I'm Kristen Lays with Heritage Preservation in Washington, D.C. and I want to thank Mike and Learning Times for helping us with this webinar and to the Institute of Museum and Library Services for making this series possible. Please feel free to continue to say hello in our chat box and in a few minutes as Mike said, we'll move that away to a moderated chat. We have Heather Brown helping us today answering your questions. She's one of Debbie's graduate students at the Art Conservation Program at the University of Delaware and we're really grateful for her help today. Today's webinar will be about the technological development of photography and we'll continue it next Thursday. So it's a two-part series and it's so important to understand how photographs were made so that you understand what kind of degradation they might experience and what kind of conditions they should be kept in. So we just wanted to again alert you to next Thursday's webinar. We'll be at a later time, so 3 to 4.30. And then the final two webinars in this series will be Tuesday and Thursday of the following week. I'm just going to really quickly go over some things because Debbie has a lot to present today. I just want to remind you that the course webpage is where you'll find all the information we are presenting to you. So after each webinar airs, we will have PowerPoint slide handouts, links to the homework assignment. We've got a great list of references that Debbie's pulled together for you and that's all there. And then after each webinar, we will email you with all these links as well. So if you're not getting our emails, do let us know at heritageinfo at heritagepreservation.org and make sure we're not ending up in your spam filter too. If you're interested, you can work towards earning a certificate in digital credential. You should have registered so we know who you are. If you're not getting our emails, that's an indication you may not have registered, so please be in touch. Watch each webinar in the course either live or in the recording and complete all five homework assignments. And if you do wish to earn a certificate in digital credential, you should have everything completed no later than Thursday, May 30th. And of course I want to remind you about the Connecting to Collections online community. If you're not already a member, this is a great place to have links to additional resources and network with each other. Okay, I'm going to welcome back Debbie in a minute, but here's our information on how to find us if you need anything, have any questions about the course. And I'm just going to ask a series of poll questions at this point just to give Debbie a sense of the audience and the types of photograph collections you might have. We're going to start off with maybe a tough question.  So each print, each negative, each slide, each lantern slide. We know it's so hard to make an estimate, but if just a ballpark would sort of give us a sense of the scope of the issue that you're dealing with. We don't know because it is challenging. I am seeing that you sometimes hear the sound cut in and out a little bit, and that's just because we're using voice over internet and it's a little like a cell phone in that regard. So we do apologize if you're on a wireless network. Sometimes there's also a slight delay. So if it's possible to close all the open programs on your computer except for your internet browser that sometimes helps. So just bear with us and hopefully the closed captioning will keep you informed if there's a blip over a key question. Okay. Thanks so much. There's lots of photographs out there, so we're glad to help you. I'm going to close this poll and drag it away. And then Debbie talked a little bit last time about some early photo processes. The garyotypes, amber types, and tin types. And I think it helped the audience to learn a little bit about, you know, that it helped them identify some of these types that they may have misidentified or weren't as knowledgeable on. So she will review that today, but we wanted to sort of get a sense before today's lecture if you had an estimate. And she'll know if she wants to go into the tail line. Great. Let me bring this back later. And then today's presentation will talk a lot about prints. Some of these terms may not be familiar to you. So if so, don't worry about it. Don't know. It's a very, very viable option. But she referenced a little bit of this last time. And again, we're going to go in a lot more detail, but it's just sort of a sense of the group and what you do not have in your collection. Okay. Thank you so much. I'm going to go ahead and close this and drag it away. And again, we may bring that back. Presentation. Okay. At this point, it's my pleasure to welcome back Debbie Hesnoris. And she, again, is the chair of the University of Delaware's art conservation program and an expert in photo conservation and a great advocate to our field. So we're really pleased that she's with us today. I'm going to go ahead and close this chat box here. And we're going to turn it over to Moderated Chat. And as Mike was saying, this means that your question, and once when we publish it, unless we respond to you privately, and you're welcome to tell us if you're having any technical concerns. But don't be concerned if you see your question twice. So with that, I'm going to hand things over to Debbie. Going through clearly. Uh-oh. Hang on. Okay, good. Okay, good. I'm reading my, Mike, who is sort of leading all of us through this, has just been terrific. And I think I'm on, and I think you all can hear me, and I'm very happy to be back for the second webinar in this series. And as Kristen described, this will focus more on the technology of photography. And particularly with this lecture, I'm going to be talking about photographic print materials, especially those that are silver-based materials. And again, I do love the Beatles. And so once again, another Beatles title, The Long and Winding Road, with some really fantastic portraits that you can see here, both black and white, silver gelatin portraits on your left. And then these wonderful dye transfer photographs all by Richard Avedon on the right. If you sort of think back to what we talked about on Tuesday, the silver gelatin photographs of the Beatles on the left. In this case, the final image material of metallic silver, the binder is gelatin, and they're on a paper support. The dye transfer photographs on your right are comprised of organic dyes, cyan, magenta, and yellow. And there is no silver at all in these particular photographs. But anyway, let's keep moving through this. I also want to thank Heather Brown, who you see here, who is a second-year fellow in our graduate program, our three-year master's level program, jointly sponsored with Winniter and the University of Delaware. And she will be online, as Greta did on Tuesday, answering questions where she can. And I hope you find this helpful, and I'm grateful to Greta. And what you see here is she's treating a wonderful silver gelatin sepia tone, which is why it appears brown in color, photograph from a wedding. And in fact, I'm going to grab the pointer again, because it's a little bit hard to see. If you study this photograph, you can see how it's much lighter at the bottom edge, whereas very gray and somewhat discolored throughout. And it turns out, in fact, that was all dirt and discoloration, most likely caused by smoking, nicotine. And she was able to carefully remove all of the dirt and grime from the surface of this photograph. So anyway, thank you, Heather, for your help. I certainly appreciate it. And again, I want to remind you that my goal in all this, there's so much to cover and there's so much we could talk about. And I thank you for your questions and the homework, which has sort of allowed me to broaden the scope on this presentation as well. But I want to keep focusing on resources, because we can only begin to address a bit of these topics. But be sure to examine the resources that are online, the links that Heritage Preservation has provided, and the many books that we talked about during Webinar 1, including these two books by Bertrand Lavadrine. And I highlight these particularly today, because they're very rich in content in terms of the various photographic processes, particularly photographs of the past, the photographic print processes that we'll be discussing today. We talked on Tuesday about daguerreotypes, amber types, and tin types. I talked about how these are direct positives. That is that these are made without a negative. You take that light-sensitive silver-plated copper support, in the case of the daguerreotype here, and place it into the camera and expose it to light. And in that way, there is not a negative. So we call these direct positive processes. And we talked a bit about these different processes and just to review, because many of you mentioned that you do have these in your collection. The daguerreotype is popular from 1840 to 1865 in the United States. And again, remember, this is a process that's on silver-plated copper. Very highly reflective. It looks like a mirror. As you hold it in your hand, it moves from a negative to a positive image. And these daguerreotypes are often housed in protective cases in the United States. In France and in Europe, you will sometimes find these in what we call passe partus. That is, they're framed behind a decorative glass and often hung on the wall. So they're not in a folded miniature case at all. So their presentation can vary around the world, but they are generally prone to deterioration, corrosion at the outer edges, as we discussed on Tuesday. In comparison, the amber type, another example which you see here, in this case, a beautiful image that's hand-colored from the Library of Congress, is on a glass support. It's not on silver-plated copper at all, but rather on glass. It has a salis nitrate or collodion binder layer in which a silver image is suspended, and then the amber type is typically varnished. And they may or may not be hand-colored. This is a beautiful example of a hand-colored amber type in really excellent condition. Remember, I mentioned that these are actually technically negative, but they were made to look like a positive. It's a very thin negative image.  And some of you had asked last Tuesday and also in questions subsequently about flaking and issues associated with flaking of amber types. This can happen at their outer edges because you do have collodion on one side of the glass and usually a black lacquer on the other. But in many cases, they actually are in very good condition because they've been protected from the intrusion of air and moisture in these decorative cases. And then finally, the tin type process that you see here, which is popular in the United States, especially throughout the 19th century. And of course, in this situation, the support is actually iron. Iron that's coated on both sides with a black lacquer or in some cases a brown lacquer. Therefore, the tin type appears more brown in color. But the image is silver. The binder is collodion. These are typically varnished and often hand colored. As you can see, at least hand colored slightly in the cheeks to make these images or these individuals appear a little bit more lifelike. The great challenge with tin types is when they're exposed to high relative humidity conditions that iron support may begin to rust and corrode. And you can only imagine, again, these are laminate structures. And so I need you all to sometimes just sit and think for a second. What is the cross section of this object? You can imagine that as the iron begins to rust and corrode, it will affect the collodion binder that sits on top of it, causing flaking and deterioration. And so that is a real catastrophic problem, really, if the support begins to deteriorate in that way. And one that you try to avoid and how do you do that through storage in controlled environmental conditions wherever possible. But for the most part, I think when you go back and look at the tin types in your collection, you'll find that they're generally in good condition. They may be rusted and corroded at their outer edges. But for the most part, these images are fairly pristine. The varnishes may have yellowed a bit. But that varnish layer does protect the silver image from fading and discoloration. It's always important when you think about these processes to, in your mind, think about a timeline, timeline of popularity. So it can begin, again, to help you distinguish the various processes. It's important to think about when they were made, when they were popular, what do they look like. All these things sort of combine. So in this particular timeline, you can see the daguerreotype, amber type, and the tin type, and their sort of dates of popularity. And this may help you, along with many other keys and characteristics that you'll read about that you might hear about, to begin to distinguish within your collection whether you have daguerreotypes, amber types, or tin types. On the fourth webinar, we're going to talk about prioritization for preservation and when you should begin to consider rehousing these collections, perhaps storing them in protective boxes to mitigate against environmental damage. But this webinar is really not today is focused more on identification. I see that Heather has been answering some of your questions as we go through. And we'll take breaks here and there, but not yet to address questions as they come up. I want to focus here, though, on photographic print materials, particularly 19th and 20th century. And I had asked on Tuesday for you all to send images. And here's one that I received from the University of Texas School of Law. A wonderful album from the 19th century, which appears to be, in this case, comprised of albumen prints. These are photographic processes that dominate the 19th century. And as you're beginning to try to identify print materials, and many of you, and identifying preservation challenges as part of your homework, talked about the difficulty that you're encountering in differentiating these different processes. So that's what I'm hoping to help you with today. But as you're beginning to do that, you need to really think about dates of popularity and what was popular in the 19th versus the 20th century. So these photographs that you see here appear in my mind, of course I'm not looking at the object, to albumen prints. They are definitely printed out. And if you remember, on Tuesday we talked about the difference between printing out and developing out images, these printed out images that are made by taking light sensitive paper, placing it in contact with a negative and out into the sun, into the image visually prints out. As a result, they tend to be brown or brownish in color. These, however, have faded fairly significantly. They're much more yellowed, which is a common deterioration problem with albumen prints. I have another one as well, which I'll show you. Really a wonderful album. We'll talk about the preservation of albums during Webinar 4 or 5. But again, you can see that although they're in different states of condition, all of these images are much browner in color. They're not truly black and white. So understanding when photographs were popular, knowing that the albumen process is introduced in 1851 and popular throughout the 19th century can help you in beginning to identify various processes. So timeline and identification is important as is deterioration. This is a wonderful image actually from the Metropolitan Museum of Art and a recent exhibition that they have now called Faking It, which I recommend highly will be traveling to other museums as well. It's sort of pre-photoshop and how photographers manipulated their images to create effects as you see here. But looking at photographs to assess their deterioration can also help you in beginning to determine whether something is silver gelatin photograph or an albumen photograph because these materials deteriorate in different ways. So identification, deterioration. Here's another example also. In this case from the Nelson-Eckins Museum of Art and albumen photograph in generally good condition, but there is some evidence at the outer edges of fading and discoloration, which is typical of silver images. So deterioration problems will help you. You're always thinking about preservation guidelines and priorities. So as we're going to focus on is this albumen, is this silver gelatin, I want to be sure that you are also always thinking about the bigger issues of preservation because really that's what's fundamentally important. In the end, to be honest, you're going to house albumen prints in the same way that you're going to house salt and paper prints. So whereas it's nice to know and important to understand these materials and their technologies, preservation guidelines and priorities are by far the most important topic. When you're thinking about identification, you think about the historical, the contextual, and the technical. And this is a Matt Kalodian photographic portrait, really a beautiful one actually privately owned. You see here mounted onto a gray card. Matt Kalodian process is introduced at the turn of the 19th century in the mid 1890s and popular until about World War I. And this is a silver based process that is actually toned with gold and platinum to produce a very permanent photographic print process that you see here. And it tends to be somewhat neutral in color. It almost appears black and white, but in fact it's a printed out image. But the neutrality of the color has to do with the toning in gold and platinum. So in terms of historical and contextual issues, just some things to think about. Who is the photographer? Do you know their dates and when they worked? Do you have a sense of where this object came from? Can you date it from that point of view? The content of the image, who's pictured in the image? Do you know who that person is when they were born and died? Do you see cars? Do you see buildings that you can date? What is it in the image itself that may allow you to begin to date that object? And also its format. Is it mounted? Is it unmounted? Is it on a cabinet card? Is it on a cart de visite? Is it a stereo view? These different formats, some of which I'll mention more detail in a moment, can sometimes be dated as well. And so all of these clues can help you begin to differentiate when might this object have been made and therefore then you think, okay, what process was popular during that time period? Here's an example actually of an albumen print on what we call a cabinet card. So the cabinet card is a format about four and a quarter by six and a half inches and this process of format is introduced in the 1850s, 1860s. In terms of the technical, you know, think about image quality and image color. So is that photograph brown and white or black and white in color? And that may help you to distinguish various processes. What is the tonality in the non-image area? Is it yellowed or is it white? For example, the albumen process has a tendency to yellow, the egg white binder yellows over time. And therefore when you look at a highlight in an albumen print, it may be yellowed and deteriorated. Whereas a silver, gelatin, black and white photograph, the gelatin doesn't tend to yellow and discolor in that way and therefore you'll see a brighter, whiter highlight. So the non-image color is something that can help you as well. Here is, in fact, this is a nice comparison. So here you're seeing a salted paper print from, as you can see here, 1855. So this is a printed out image in which the image color is very brown. It's a photolytic silver image. And in comparison, this photograph by Man Ray is black and white. You can see the difference in the image tonality in those dark areas and also in the non-image color here, which is very white and bright. But also you want to look at surface characteristics. Is that image glossy or matte? One thing that we often talk about when we're trying to differentiate the photographic printing processes is whether they are a one, two, or three-layered structure. A one-layered structure is something like the salted paper print where the image material is embedded directly in the paper support. And I'm going to go back because I can. And in this case of the salted paper then, the silver image is actually embedded in the paper support. They tend to be very matte. They aren't glossy. Now, this photograph may be an exception. It seems to have a bit of a gloss. And that could be because it's coated with a varnish of some kind. But for the most part, this one-layered structure, such as the salt print, the image is embedded in the paper support. Whereas in other photographic processes, you have a binder, such as albumin, collodion, or gelatin. And we call that a two-layered structure. In that case, the surface will appear more glossy and not as matte as the salted paper print. So being able to differentiate these various layers and what's present and what the surface character looks like can also help you to differentiate one process from another. Format and presentation, as we mentioned earlier, can also help you. The silver gelatin photograph, as you see here, they are often unmounted. The albumin print is typically mounted because it has a tendency to curl. And of course, deterioration characteristics. Is there image fading, which is characteristic perhaps of a silver image? Is there cracking of the binder layer, which you may see with the egg white binder, albumin, et cetera? So here's a cross-section of some of the photographic processes that we will talk about, not in great detail for all of them. But you see with this timeline a sense of the chronology of these various processes. I've shown you some of these throughout the lectures already. Beginning with the salted paper process, which you see here, introduced in 1841. I can't move my... I have a bit of a technical problem. My pointer is stuck. Got it. Okay. Here you go. So the salted paper print, which you see here, starting in 1840s, the cyanotype process was also popular, introduced at least about this time. It really became more popular by the end of the 19th century. The albumin print introduced in 1851 dominates the 19th century. We're going to talk in much more detail about albumin, because many of you said that you had this in your collection. And then the turn of the century things become a little tricky with a variety of different processes introduced, including silver gelatin, printing out paper, which you see here, and a variety of papers, both matte and glossy, that you see here, that are comprised of collodion as a binder. And also the turn of the century, an entirely different process, the platinotype or the platinum print, which was used particularly by fine art photographers. But again, this chronology will help you to begin to differentiate what you have in your collection. And you'll see this in a variety of different publications presented in many different ways. So here's, again, the same information formatted in a slightly different way, the timeline of popularity, one process that was not on the earlier timeline, which you see here, is the silver gelatin developing out process, which is present even today, black and white photography. So study those. We don't have time, really. I don't want to go into this in an enormous amount of detail, but I just want you to be aware of the fact that as you're thinking about identification of the materials in your collection, that you're really thinking about what processes might have been popular at what different time periods. The other thing to recognize is that many of the photographic prints in your collections are likely to be silver-based. That is, they are based on the light sensitivity of silver halides, silver chloride, silver bromide, and silver iodide. Many of the silver-based processes are here at the bottom of this slide, including the salted paper print, the albumin print, the silver gelatin printing out paper, and the silver gelatin developing out paper. So all of these processes are based on the fact that these silver halides are light sensitive. With the printing out process that we talked about on Tuesday, you take this light sensitive paper, salted paper albumin, silver gelatin or cody and chloride, and you place it in contact with the negative and out into the sun until the image begins to print out. These images tend to be brownish in color when they're produced. The silver, if you could look at it under very high magnification, would be rounded in shape. It scatters light and therefore appears more brown in color. With developing out images, as we mentioned, you take that light sensitive paper and you place it in contact in an enlarger. Oh, what happened to that? There it is. And you actually expose it in a darkroom in an enlarger and then develop it in a chemical developer. So there is no light and you end up with an image that's more black in color, a final image material that's known as filamentary silver. These filaments of silver that almost resemble steel wool, the image appears black in color because those filaments absorb light. But in all cases, whether these images are produced through development or printing out in the light, in the sunlight or through chemical development, they must be fixed to remove the residual unexposed light sensitive silver salts. So all these processes, no matter how they're produced, are fixed in one way or another so that they're no longer light sensitive. And sometimes you'll hear about fixation or fixing using something like hypo or sodium sulfate. And then finally, these materials must be washed to remove the residual fixing agent, whatever that might be. And so this is sort of just a basic understanding of these materials, whether they're salt and paper prints or human prints or silver gelatin developing out. And I think it's important to get a sense and to sort of recognize what's happening as we talk about these processes in a bit more detail. And also to refer back to the cross-section which I showed you on Tuesday and that is just to remind you that you do have these laminate structures with photographic print materials that include paper supports that may or may not be, grab a pointer again, that may or may not be coated with what we call barita, which you see here. It coats the paper, it's a mixture of the white pigment barium sulfate combined with gelatin coated on the paper support. This is popular with photographic processes after 18, I would say after 1880, 1890. A binder layer which is coated on top of the paper or on top of the barita layer, transparent layer such as albumin, collodion, and then that final image material which scatters light. More importantly I think is to look at this in a real photograph. So this is a silver gelatin printing out photograph that you see here and here again the primary support is paper, you really can't see that. But under high magnification you can see this white coating on the paper support and that's the barita layer. And then of course on top of that is the gelatin binder layer so we're to see here it's folded over in the area that's damaged. The final image material is printed out silver. This is what we call a three-layered structure because we have the paper support, the barita layer, and then that transparent binder layer. So again you might have a two-layered structure, a one-layered structure, or in this case a three-layered structure when you're looking at various photographic printing processes. Okay, so let's, Kristen I think what I'll do, let me talk just a bit about salted paper and then I will stop and take some questions. I know Heather, it looks like Heather's been answering questions as we go through. But let me just start with the salted paper process which I'm only going to address briefly. It's really a beautiful process and many of you will have some of these materials in your collection. You're unlikely to have large collections of salted paper prints which is why I'm not going to spend a lot of time on it. On the other hand it's an important process to recognize because it is one of the earliest photographic printing processes. It's based on the light sensitivity of silver halides, in this case silver chloride. And it's actually produced in a relatively simple way. Photographers would take good quality writing paper, 100% rag paper that's made from cotton and linen. It was typically sized with gelatin or starch and they would then immerse that paper in a solution of sodium chloride or table salt, which is where the name comes from, salted paper. The paper then would be allowed to dry and to make it light sensitive because remember thinking back to those silver based printing processes, the sort of basic information I presented, you need silver halides are what's light sensitive. So to make this paper light sensitive the photographer would then immerse it or float it or brush it with a solution of silver nitrate, forming light sensitive silver chloride in the paper support. That light sensitive paper would then be placed in contact with a negative, which may be a paper based negative or a glass plate negative depending on when this print was made, placed out into the sun into the image actually prints out, removed from the sun and then fixed and washed. So that's in a nutshell, that's the salted paper process. And it is important to sort of think about it and to sort of understand how this process is made because it will help you to really understand all of the printing out processes. In this image here, this really wonderful image of the moon from the Library of Congress which has a fantastic collection of salted paper prints. There's an interesting actually survey of salted paper prints being done now at Harvard University and so you may find more and more information as we learn more and more about the salted paper print from our colleagues at Harvard. But when you look at sort of a schematic which you see here of the salted paper process, you have a paper support and embedded in the paper support are these silver image particles, which are actually photolytic silver, silver that's produced by light, because this is a printed out process. So the image is photolytic silver, the support is a cotton rag paper, and there is no binder layer so it's a one layered structure. This is an image of Henry Falk's Talbot's printing establishment in the United Kingdom and I showed this to you so this is where many salted paper prints are being made. Just so you can get a sense of how this is all done. These are the printing frames that are out in the sun with the light since the paper. The assistant who sort of monitors the printing, it was very labor intensive because you had to sort of determine when that print was completed when it had been exposed to light exposure appropriately before it would be fixed and washed and you can see the photographers and everyone working outside as well. So and then images here from Mark Osterman and George Eastman Health just showing a historic photography and the making of a salted paper print here. The salted paper print again introduced in 1841 popular into 1860. There is no binder layer. The image is directly embedded in the paper support. The image is a photolytic silver image. It's brown in color. It's produced by light through contact printing. It can be sort of a purplish brown color when it's in good condition but the image can fade. When you look at the outer edges of this particular photograph you will see characteristic, very characteristic fading at the outer edges as this silver image is exposed to poor environmental conditions, oxidation. It will begin to fade. The silver will convert to silver salts. The silver salts no longer absorb and scatter light as effectively and you get this characteristic fading at the outer edges. And the image of course may also be abraded because they are soft and sensitive. Here's another salted paper print. I might have shown you this on Tuesday. Just one of my all-time favorites in this case. Really quite beautiful. Someone I just glanced down at the questions and someone has asked if salted paper prints were varnished. And that is a great question and in fact many of them were because when you varnish these images you would increase their luminosity, increase their detail. And so you will find salted paper prints that are coated with a variety of different varnishes really from shellac to natural resins of all kinds. These varnishes may deteriorate in yellow over time. And this is where process identification can become very tricky because I'm telling you that the salt print is matte because the image is embedded in the paper support and yet it may be varnished or coated in which case it will be very glossy. So you need to study these images carefully and determine do I have a varnish or is that a binder layer? And what am I seeing? Sometimes you can distinguish varnishes because they've been coated by hand they've been brushed on and so you'll see brush strokes which you won't necessarily see with other binder layers. So let me just take a break and ask Kristina if there's any questions that are coming through that I might respond to before we move into the albumin process. Okay. But, you know, Kristina, before I turn it over, can I take it back for one second? Sure. Is that hard? I wanted to just show this just to finish up on the salt print because I forgot I had added this in actually at the last minute. But this is just detail under high magnification of the salted paper print which you see behind it. And what I wanted to show you here is that when you look at these images under very high magnification you will see the paper fibers and that's what you're seeing here. And again, this is symptomatic of a one-layered structure. If you have access to handheld magnifiers that are 30 or 40x, you can begin to see this yourselves. And so this identification, microscopic identification can be helpful to you. And again, why are you seeing the paper fibers? Because this is a one-layered structure with the image material embedded in the paper support. Okay. Kristen, sorry. No problem. Heather's been doing a great job answering a lot of these questions. But one that she wanted your input on had to do with popularity of these items. So Margaret had asked of the four processes at the turn of the century what would have been the cheapest and easiest for an individual to use and what was the most popular around the turn of the century because that might mean it dominates. Yeah. That's a good question. The turn of the century is the turn of the 19th century. So we're talking late 1890s through like 1910, I imagine. That is a tricky time for process identification. There are many processes that are available to photographers and it is a little bit hard to say what was the most popular. We have some photographers who are still using the albumin process. Certainly you do not see salted paper prints. Salted paper prints are popular until about the 1860s. I say that. I hesitate because there are photographers who suddenly said, oh, let's do salt prints. But for the most part, you don't see salted paper. You may see some who are using albumin. I would say the most popular process are probably the other printing out processes. Silver Gelatin printing out papers including chloride printing out papers both matte and glossy. But by 1895, Silver Gelatin black and white photography is also available. It doesn't really become popular until 1910 or so. But you can see a wide range of materials at this time period. And some of this will also depend on where you are in the world. And one book that I, and I see actually it looks like Angelica has mentioned it ironically at the same time that I was thinking about it, which is really a wonderful resource. And I will bring you an image of it in my next webinar so you can take a look at it. It's a book by Jim Riley on 19th century photographic print processes. It is truly excellent about these various processes, particularly those that dominate, of course, the 19th century based on this title. And it includes details on how these materials were made, how to identify them. There's a wonderful process identification chart in this book as well. And so that combined with the graphics atlas and looking at the turn of the century will help you to begin to differentiate some of these processes. That's great. And we did have a question about the salt process. How long did it take to produce in the sun? And was it ever done under artificial forms of light? OK. Good question. Artificial lighting wasn't really available at the time that the salted paper process was popular. And so it was produced with the sun. In terms of the length of exposure, it really varied because it depended on the sensitivity of the paper and the density of the negative and the type of negative that was being used. Was it a waxed paper negative, which was popular early on at the beginning of the salted paper print, or after 1850 to 1851, was it a wet-plate collodion negative? So it's hard to say, but I would say in general, you probably are talking about light exposure in the range of 15 maybe to 30 minutes. And it wasn't really an issue because you just put these photographs in printing frames and allowed them to be exposed to light. Of course, it had to do also with the intensity of the light and the time of year. But photographers began to sort of recognize what their exposures would be based on their own experience. There are many, many variables. Photography was difficult, it was challenging, and it's important to step back and recognize the amount of time that went into every one of these images that we're caring for today. And actually, there's a great follow-up question from Dennis about these types of photography. Was this prohibitively expensive at the time, or would amateurs have used one type over another? The salted paper process wasn't necessarily... Well, in the United States it was expensive because it was patented, so you had to buy a patent. You had to pay by a licensing fee in order to make salted paper prints. So amateurs really were not as involved in photography. In fact, they really were not involved in photography until later in the 19th century when it was just a little bit easier to do and you could buy paper that was already manufactured and light-sensitive, such as silver gelatin printing out paper. But it wasn't, I don't think, as expensive as something like the daguerreotype. But certainly it was not a process that you would find amateurs working with. Now there were scientists who might have been experimenting with this process and dabbling in salted paper, now human prints as well. But the amateur market really begins to rise at the late 19th century with the introduction of other processes. Okay. I think, Kristen, I should keep going. Sure. Given the time, it's getting away from us. And move through albumin, at least. And then, of course, Heather, it looks like is answering questions and we'll take another break or so, and I want to be sure we have time at the end, which may be a challenge. But anyway, if you understand the salted paper print, you will certainly readily understand the albumin photograph. The albumin photograph dominates the 19th century. You see two examples here, one beautiful hand-colored albumin photograph on the right. And in this case, and another example here from the Library of Congress, when you look at this portrait of Abraham Lincoln, you can begin to see some of the characteristics of the albumin process. It is a photolytic silver image produced by light. The image is therefore brown in color or purplish brown in color. It's not black and white. These rounded particles of silver that scatter light. The binder is egg white or albumin. And this binder tends to yellow over time. And so you don't see bright white highlights, but rather the highlights are more yellowed because of the degradation and deterioration of that egg white binder layer. The image tends to fade. Both of these images are somewhat faded. And if you could look at this photograph under higher magnification, you might see cracking, which is a common problem with albumin as the egg white expands and contracts differently from the paper support. There are all kinds of wonderful videos and movies online that show you how albumin prints are made. I've just done a few screenshots from this particular video that's produced by the George Eastman Health, and I mentioned these in my discussion on Tuesday. They're really wonderful in terms of sort of showing you how these materials are made. But to make an albumin print, of course, you would take the white of hen's eggs, which you see here, and that would be then beaten up to a froth to homogenize the egg white. And a salt of some kind, such as potassium iodide or ammonium chloride, would be added to that egg white binder. The lightweight paper support would be floated on this albuminized solution, which you see being done here. And to make that paper then light sensitive, you would take the albuminized paper, that is paper that's coated with egg white, and float it on a solution of silver nitrate, forming light sensitive silver chloride, most likely in the albumin binder layer. That light sensitive paper then would be allowed to dry, placed in contact with the negative, typically coating wet plate negative as you see here, and placed out into the sun until the image begins to print out. And again, the image that I showed you earlier, showing the printing frames out in the sun as the photographs are printing out. And you could inspect, as you can see here, the extent of printing by just carefully lifting up the image to see. In this case, you can see this albumin print, which is printing out following exposure to light. The photograph would then be fixed with sodium phthalate or hypo and washed. And after 1854, I would say, really, this is part of the process. This photograph would be gold toned as well. And so the process really is that you expose the albumin print to light, you then gold tone it, fix it, and wash it. And so these images are traditionally gold toned. And the gold toning would improve the color and certainly increase the permanence as well. So albumin prints in very good condition tend to have a beautiful, purplish, brown tonality. Here's another sort of schematic that begins to sort of describe silver printing out papers and albumin prints in particular. Again, you take that light-sensitive paper, you place it in contact with a negative, you tone it in a gold toner of some kind, you then fix it to remove the unexposed light-sensitive silver halides and wash it. And you end up with an image that has a brown or purplish image color. And under very, very high magnification, 40,000 X, you will see these tiny little particles of silver metal, these rounded particles that scatter light, and therefore the image appears brown in color. So the albumin process is made by taking this albuminized paper, making it light-sensitive, exposing it to light, and then toning it, fixing it and washing it. The paper tends to be very good quality, but it's also very thin, tends to curl. And for that reason, most albumin prints were mounted in some way, as you see here. So you may hear a reference to something called the carte de visite. And the carte de visite refers to a format, which is about 2 1⁄2 by 4 ¼ inches. And these are all albumin prints that are mounted onto these various carte de visite formats. Now, a carte de visite is not always an albumin print and certainly in places like Western Europe, many carte de visites are actually matte collodion processes. So be very careful about distinguishing the format from the process. On the other hand, in the United States, I would say that 95% of the carte de visite that you find in your collections are likely to be albumin prints. This is simply because the carte de visite mount, this format, is introduced in the 1850s at the heyday of albumin printing. All of these albumin prints are in relatively good condition, but you can see they're all brown in color. They all have yellowed highlights. This is, again, the deterioration of that egg white binder layer. Some are faded at the outer edges, which is typical of silver images. But they're generally in good condition. Another format that you may find in your collection that's popular with the albumin process, but you'll see this format into the 20th century as well as the cabinet card, which is slightly larger. In this case, probably about four and a quarter by six and a half inches. These are two albumin prints, in this case, mounted onto this cabinet card. So you want to think about format and think about process simultaneously. Another example here of an albumin photograph from the Library of Congress in relatively good condition with some fading, certainly at the outer edges, but the cabinet card refers to the format and the size of the mount. When you look at the albumin print then in cross-section, what you'll see here is a two-layered structure. You have a good quality, 100% rag, thin paper support coated with a transparent albumin or egg white binder, and the image material is this photolex silver, these rounded particles of silver metal that are toned with gold. So you have a gold-toned silver image, an egg white binder, and a good quality paper support. The process dominates, as we said many times, and it's worth repeating the 19th century. When we did that poll at the beginning of this lecture, many of you said you had albumin prints, which is not the least bit surprising because they are so common. And again, it's an egg white binder on a very thin paper, typically mounted, typically gold-toned with this purplish-brown image, and yellowed highlights. Again, the highlights are yellowing because of the deterioration of the silver image and also the deterioration of that albumin binder. And the egg white does tend to crack and craze over time, and so under high magnification you'll see this characteristic cracking, which I'll show you in a moment. I also wanted to draw attention to another problem in 19th century photography, and that is we do begin to see fading of the highlights. The highlights lose their detail. Fairly rapidly, and this is because the silver image in those areas is very small and very prone to fading and deterioration. So one of the first areas where you'll lose detail is in areas of highlights, such as christening dresses, which you see here. This is an example of that cracking that I talked about, which is characteristic of the albumin process, as that egg white expands and contracts differently from the paper support. You get this characteristic cracking, which you will not necessarily see in something like a black and white silver gelatin photograph. Again, there are all kinds of resources, and through the IPI Image Permanence Institute website, you can purchase a book that was written many years ago and has now been updated by Jim Riley on albumin and salted paper. And this is a wonderful publication, really, which outlines how these materials were made, how they were manufactured, how they were mounted, the different kinds of mounts that were used and how they deteriorate over time. So I recommend this, certainly. And again, an awful lot of information that we're talking about can be found on the graphic set list. So keep referring back to these various resources. I wish we had hours and hours and hours, and we could talk for hours and hours about the albumin process. But it's nice to know that there is an enormous amount of information out there that I think you will find very helpful. But in the back of your mind, I've gone back just to remind you again that the albumin process has this brown and white color. Now, this particular albumin print is not in particularly great shape. It's yellowed, it's faded, there's loss of highlight detail. It has surface dirt and deterioration as well. But it is characteristic of the albumin print. I'm going to just introduce a couple of processes that I want to move quickly to Silver Gelatin developing out, because that's the other process that you all identified and the one that's most common in your collections. But someone had asked earlier, you know, what dominated the turn of the century. And this is where we get into all these other processes, one of which is Silver Gelatin printing out papers, which you see here. And these papers were introduced, as you can see, in the 1880s, late 1880s, and popular really until 1940. What's different here is that photographers would actually buy this paper already manufactured. They no longer had to sensitize them to light. They didn't have to deal with immersing things in silver nitrate. When you bought, typically, with the albumin process, a photographer would purchase albuminized paper, which was manufactured in Europe. But he or she would have to float it on a solution of silver nitrate to produce light-sensitive silver chloride. And that was cumbersome and difficult and time-consuming and problematic. With the introduction of Silver Gelatin printing out papers, these papers were made by machine. Good quality paper was coated with a Gelatin emulsion, a Silver Gelatin emulsion. And photographers would buy this light-sensitive paper, place it in contact with a negative out into the sun so it's still printed out. You still have that characteristic printing out color that you see here.  They are traditionally toned with gold fixed and washed. But the way they produced is very different in that photographers could now begin to just purchase these materials. The other difference with the Silver Gelatin printing out paper is that, for the most part, these are three-layered structures. And you can even see, it's hard to see here, but you can almost imagine that the surface quality is much glossier. Because in this case, the paper is coated with that burrida layer, that barium, the white pigment barium sulfate and Gelatin coated on that paper support. And so you can get a surface that's much glossier because you no longer see the paper fibers. They're hidden. It's like icing a cake. Whereas with the Albumin print, you still have the paper fibers that are visible. You're looking through that clear, transparent egg white layer. And so the Albumin photograph will have a bit of a gloss, but it's not as glossy as the Silver Gelatin printing out paper. Again, if you go to the Graphics Atlas and experiment with this, you'll be able to see, you can compare Silver Gelatin printing out paper to an Albumin paper, and you can see how their reflectance in their gloss is quite different. One of the problems, though, with the Silver Gelatin printing out papers is that the Gelatin may expand and contract differently from the paper support and the burrida layer. And at the very bottom you can see here, these images do tend to flake at their outer edges, particularly when they're exposed to poor environmental conditions. They, too, can fade and discolor, although this Silver Gelatin printing out photograph is in really excellent condition. And here is the detail of that. So you can see where the image has begun to deteriorate. You can also see the burrida layer again here, that white pigment coated with Gelatin. And under high magnification, do you see how you don't see any paper fibers? It's very smooth, very glossy. One thing you do see with these photographs, though, if you look at them very carefully, is retouching. This is retouching in the eye, and also in this case on the eyebrow, to make these individuals look a bit more lifelike. It's not something you'll notice right away, but in many cases there's a little bit of pigment applied to the eyes, and sometimes to the cheeks as well. We also have another process that's popular at the turn of the 19th century, collodion chloride papers, both matte and glossy. And collodion simply refers to the fact that in this case the binder layer is collodion, or cellulose nitrate. These two are manufactured, so you would buy collodion or Gelatin papers. They also are printed out, but the collodion chloride process is typically toned with gold and platinum, and therefore these images appear more neutral in color, and they sometimes can be, often, can be confused with black-and-white silver Gelatin papers. They tend to be in excellent condition. These are both beautiful in terms of their condition because of the toning of gold and platinum. But they can be abraded, and if you look carefully at this particular photograph of the baby here at the outer edges, you can see evidence of abrasion, and this is because collodion as a material is brittle, and it does abrade quite easily. But for the most part, if you have a photograph, and they often, here's another tip, they're sometimes mounted, often mounted on, not neutral, but rather gray mounts, and I think this simply has to do with the fact that they look better on these gray mounts. So you have photographs in your collection from the turn of the century that are neutral in color, that are mounted onto a gray mount. They could be matte collodion, as you see here. There's also, and this is where it all becomes very confusing, so stay with me. Don't despair. But there's also glossy papers that were made with collodion, as you see here, and so this is a collodion binder layer, a silver image on a bright-acoded paper support that have a very high gloss, very similar to silver Gelatin printing-out papers. Sometimes they added dyes to the collodion or to the paper support to produce images that were very blue or purplish-blue or magenta in color, as you see in this photograph of Kaiser Wilhelm on your right. And this, in fact, was common for those of you who are tuning in from Eastern Europe, from Russia, from that part of the world. These tinted collodion chloride papers were very popular and very common, not as common in the United States, but you still will see them in your collections. And you'll see them, really, around the world. One thing that distinguishes both of these photographs is they're in very good condition. That collodion binder layer protects the silver image. Unlike a Gelatin material which can expand and absorb moisture, become tacky and sticky, collodion doesn't respond in that way. It's a form of psalus nitrate. This is the same material that we encountered in amber types and tin types. So these are collodion chloride glossy papers that also were very popular at the turn of the century. Now, the other process that I want to talk about, and then I promise to take time for questions, but I want to be sure to address this, is silver gelatin developing out or black and white photography? Because when you responded to the polls, many of you said we have albumin prints and we have silver gelatin developing out photographs. The other day, someone asked whether silver gelatin or gelatin silver. And it can be either. People use both terminologies. I wish that it was a bit more standard, but it's not. But silver gelatin refers to the fact that the image is silver. The binder is gelatin. And developing out simply refers to the fact that these photographs were produced through development, through chemical development in a dark room, and not by light. And you see here, too, photographs in generally good condition. This one is an excellent condition. This photograph is much more faded, yellowed, and deteriorated, which is typical of some of the deterioration problems that we see with black and white photography. One of the main problems that you see here in these silver gelatin developing out photographs is mirroring. And so with the photograph on the right, you can see where the image is actually deteriorated in those areas that were probably exposed to a poor quality matte of some kind, so that the center area was protected. This area was placed in contact with this poor quality matte, causing the silver image to deteriorate, or what we call mirror. This is actually a migration of the silver in the photograph where it migrates through the gelatin binder layer and then is deposited on the top surface, as you see at the bottom edge. A common problem with silver gelatin developed out photographs. Again, just a reminder of where we are at this point. We're now into the 20th century, and this black and white developed out papers that began to be popular by 1905 and are certainly popular into the 1960s when they were replaced with color photography. You can see that shift in color, I hope. The photolytic silver images that are brown are in color, and here we are at the turn of the 19th century into the 20th century with black and white images, the silver gelatin developed out process. And here is another comparison, printed out versus developed out, printed out produced by placing paper in contact with the negative out into the sun, and the silver gelatin developing out paper produced in the dark room. Both photographs, in this case, in very good condition. So a schematic here is you take that light-sensitive paper, you expose it to light in an enlarger, you immerse it in a chemical developer, you take it in a dark room, you then fix it with sodium phthalosulfate to remove the unexposed silver halides and wash it. These images are often not toned. Toning is very common with printed out images, not as common or as necessary really for permanence with the developed out image. One thing I wanted to be sure that you saw is the size and morphology and shape of the silver image, this filamentary silver, these clumps of silver that absorb light, and therefore the image appears black and white. In cross-section, again, you've got a good quality paper support of some kind coated with borita, and then a gelatin binder and a filamentary silver image, that black and white image that we've seen. A wonderful resource for all of you is this guide to fiber-based gelatin silver print materials, their condition and deterioration by Gowan Weaver. This is listed in the resources. It's available online, and Gowan has addressed the many issues associated with the appearance and deterioration and preservation of these black and white silver gelatin papers, which can be very different in their surface quality and characterization. There is considerable work being done now by Gowan, by Paul Messier, by the Museum of Modern Art, by the Image Permanence Institute, and many others. Trying to characterize the surface of these silver gelatin papers, because they can be very glossy, very matte. They can be textured to resemble a canvas, weave, or a fabric of some kind. And in your collection, you'll see examples of these different materials. Notes on photographs, which I mentioned before, has extensive material in black and white papers. Paul Messier, who works privately in Boston, Massachusetts, has assembled a large collection of silver gelatin developing out papers, which are now being studied, to begin to characterize their surfaces and understand their manufacture. And much of this information is online on his website. So if you're interested in learning more about 20th Century black and white photography, this is another resource that you may want to refer to. This is just from Paul, actually. You get a sense of the various papers that he's been purchasing and studying, all the different textures. And this has been very important to us in the field of photograph conservation, as we begin to characterize the kinds of papers that various photographers use during their lifetime. The quality, the fiber content, the thickness of the burrata layer, et cetera. And there's a lot of work going on in this area. But in your case, I think what's important, here's a great photograph with Paul McCartney, of course, is just to think briefly, you know, what is this developed out photograph? It's made through chemical development. The development has stopped. It's been fixed and washed. And you end up with this image that is when it's in good condition in black and white. And as you see here, again, it's produced through chemical development as opposed to printing out. So you can really begin to differentiate in your collection these different materials. The developed out image is black in color. The filamentary silver image is compared to that printed out browner image. In this case, both of these images are in relatively good condition, but you do begin to see that mirroring at the outer edges, which is characteristic of developed out papers that have been exposed to poor environmental conditions. Unfortunately, these silver images do deteriorate. And in this schematic, which comes from Gowen's publication, which you see here, what's happening is these filament bundles as they're exposed to poor environmental conditions with the intrusion of air and moisture, pollutants in the air, poor quality enclosures, they begin to break up and begin to disassociate. And as they do, the image converts from something that's black and white to something that's browner in color. It no longer absorbs light as effectively, and the image appears faded and discolored. And so that's what's happening with many of your black and white photographs that appear brown. That's actually deterioration of that silver image. Some of your black and white photographs may in fact be intentionally brown or sepia toned, as you see here. And this sepia toning was common in the 1920s, 1930s, where a black and white image was intentionally toned with sulfur to produce the silver sulfide image, which is actually usually in very, very good condition. And they are, again, popular during that time period, but they are technically silver gelatin developing out. They were often hand colored. Here's another one of these great postcards from the Image Permits Institute, a sepia toned silver image that may in this case be hand colored or printed. But the sulfur toning allowed for this hand coloring because you weren't competing with a black and white image, but rather hand coloring something that was browner in tone. So this process then, you know, dominates the beginning of the 19th century. The paper tends to be coated with burrida, but the surface can vary. It may be very glossy or very matte, depending on the thickness or thinness of that burrida layer. There's a silver image embedded in a gelatin binder. You will see image fading and silver mirroring.  This still appears black in the dark areas. Silver gelatin developed out photograph with this characteristic mirroring. And also you can even see the characteristic surface quality of this photograph, which has more of a textured appearance. And that was really part of the process. Another example here also faded and deteriorated. Some of these photographs take on sort of a greenish-yellow appearance that you see here. And the silver mirroring, again, is very common with these photographs from this time period. Someone submitted this, University of Texas School of Law, also submitted this image on Wednesday, and I just wanted to pull it up and show you here. So this is a black and white silver image, but it looks very peculiar, because it's been extensively retouched. And probably retouched, so that it would then be re-photographed for a magazine or for publication purposes. So in your collections, there are photographs that are retouched to be exhibited, and then others that are extensively retouched because they're going to be re-photographed and printed in magazines and newspaper articles as well. So that's what's going on with this particular print. These, you know, the bottom line with these black and white silver images is that they do deteriorate. In fact, it's true with all silver images. Albumin prints, salted paper prints, and silver gelatin developing out photographs as well. And this fading is caused by exposure to high-humidity, air pollutants, poor-quality enclosures that cause these silver images to change, as you see here, to convert to silver ions, silver plus. And these silver ions form silver compounds that do not absorb and scatter light as effectively silver sulfide, silver sulfide, and the images appear faded and discolored, which is true with all these photographs that appear somewhat greenish-yellow in color. Some of this is caused by exposure to poor environmental conditions, most of it, in fact. But in other cases, it may be improper processing, improper fixing and washing. So you'll see with all these silver images fading, as you see here, in discoloration, silver mirroring, which is a migration of the silver in the binder layer being deposited on that top surface. You can see silver mirroring wherever you have silver, and a binder layer of some kind, but it's much more common with silver gelatin developing outpapers. And then finally, yellowing is another problem that you'll see with the deterioration of the silver image material as that black-and-white image or that photolytic silver image reacts with other products. You begin to form silver sulfide, which is yellow in color or brown in color. So you start to see with your photographic collections, and many of you in your homework, talked about silver image deterioration as one of your challenges. You start to see these different problems, fading, silver mirroring, and yellowing. And the way to mitigate against that is proper storage, controlled environmental conditions that will begin to slow down the rate of deterioration of that silver image, whether it's photolytic or filamentary in shape. I want to, and then I'm going to open this up for more questions and try and help those of you who may be confused, it is confusing. There's just so many photographic processes out there, and I think it's really important for you all to just have a bit of a handle on these silver-based processes and not worry so much about the non-silver print materials, which you see listed here. There are many of them. But by non-silver, this simply refers to the fact that there are a whole host of photographic printing processes that are based on the light sensitivity of other materials, such as bichermates or iron salts. Iron salts are light sensitive, and so you can produce using these materials cyanotypes or platinotypes or the carbon print. And you may have these in your collection as well. This is a carbon print here, in which the final image material is actually a pigment in a gelatin binder layer. The ones that are most common are the cyanotype, which is a blueprint, which is easy to identify based on its color, popular throughout the 19th century, based on the light sensitivity of iron salts, with the final image material actually being the blue pigment, Prussian blue. And these materials, one of the greatest problems with cyanotypes is they do fade sometimes in the light. So you have to be careful with light exposure. But for the most part, they tend to be in relatively good condition. But there is no silver here, so you're not dealing with the kind of fading that we've seen with the albumin prints or the silver gelatin developing out photographs. And then finally, the platinotype or the platinum print is another process that we're not going to address in an enormous amount of detail, but I just mentioned it here. As a non-silver process, the final image material, in this case, is actually metallic platinum embedded in a paper support, much like the salted paper print, based on the light sensitivity of iron salts. One thing you see happening here, which is common with the platinum process. This paper was in contact with the platinum process and you can see a transfer image.  And so in the areas of platinum metal, these dark areas, it has caused the paper support to deteriorate. You might see this in photographic albums sometimes, where this image transfer can be caused by inks as well, but in this case, it's caused by contact with that platinum metal. But whereas platinum is a catalyst for deterioration, it is a very permanent material. Some of you may have wedding rings that are made of platinum, and it doesn't fade or tarnish or corrode like silver. And for that reason, these platinum prints tend to be in good condition. You won't see mirroring. You won't see fading. However, you may see paper deterioration because it does catalyze that deterioration. And also because it's based on the light sensitivity of iron salts, those iron salts can cause the paper support to fade and deteriorate. Here's a wonderful platinum print by Gertrude Kasebier. I mentioned that Greta had done research on her work. As a second-year student, here's another photograph by Kasebier. You can see it's in great shape. It's a neutral color, which is typical of the platinum print. It may be a little yellowed and faded in the paper support, but the image has not deteriorated in the ways that the silver gelatin developing out or the albumin print has. Under magnification, you will often see paper fibers, as you do with the salt print, thinking back to that cross-section, because this is a one-layered structure. In the platinum print, the final image is actually embedded in the paper support. So with that, I have a few more slides, but I'm going to take a break because these are more of a review. That's sort of a whirlwind, but the most important points here are to just step away and recognize that there's a wide variety of photographic printing processes that are available that are present in your collections. Probably most of them are silver-based. Your photographs from the 19th century are most likely printed out silver images, probably albumin prints. They may be salt prints if they're earlier. They may be silver gelatin printing out or chlorine chloride printing out if they're turn of the century. And in the 20th century, these silver-based processes tend to be developed out. But in all cases, they are prone to fading deterioration, mirroring, and this deterioration mechanism can be controlled through proper storage and environment. So with that, Kristen, let me turn this over to you for a few questions that may have come up that I can help with. And then I do want to come back to this sort of review at the end. Okay. We have so many, and I know Heather's working quickly to answer them as well. And some of the more straightforward questions I think she's doing a great job on. We just want a clarification on terminology that Ilka had, the difference between process and format. And Heather explained that to her. And I guess the reason Ilka brought this up is that in a catalog description, it should be important to indicate photo process as well as format. So an example would be that it's this process on a card or... Yeah. Yeah. You know, again, gosh, I wish I had you all in an auditorium, and I could lock the doors, and we had lots of time. As I was saying that, I was thinking, oh, you might be confused. Process refers to how that photograph was made. So an albumen print, a silver gelatin developing out photograph, that would be process. And format, of course, is more about the size. And some of these formats are standard, such as the card to visite, the cabinet card, the stereo view. But many are not. And this, in terms of cataloging, it's really up to the institution. It's very important where you can to identify process. And format is just additional information that can be most helpful. But many institutions, rather than identifying the format, if they're uncertain, they just simply provide the dimensions. There are, throughout the history of photography, a variety of formats that were popular at different times. Some of them are paper-based. Some of them refer more to presentations like photographic buttons. So there's a wide range of formats that are out there. And process is certainly the most important way to identify something through cataloging. Great. Kind of a humorous question that came up about albumen prints. If you were to work on a restoration of an albumen print, would you use egg whites, right? Would you need to get a 19th century heritage breed egg to do that accurately? Well, actually, if you are being involved in the conservation treatment of these things, you are unlikely to use egg white in any way. But if you're trying to duplicate a 19th century process, which is probably what we're referring to here, that's a great question. And actually, if you speak to those, Mark Osterman, Doug Munson, and others who are producing albumen prints today, they can speak with great authority about the various kinds of eggs that work and others that don't, whether they're organic or not. And it can be challenging, actually, because the eggs are very different. And the other interesting and sort of fun part of all this is what do you do with all the yolks? And you can imagine when they're producing, you know, reams and reams of albumenized paper in what is now Belgium and the Netherlands that part of Europe. There's a major challenge about what to do with the yolks, cheesecake recipes, tanning, and that kind of thing. But it is a very good question. And it is actually an issue and a problem. And sometimes when you're making albumen prints using historic techniques, you will run into problems, depending on the eggs that you're using. And Janine had a question about it. And I'm not quite sure I'm getting at what she's saying, but it crossed my mind. Is there any issue with the fact that that's an animal product in a collection? Is there any sort of test issues? No. That's a good question in terms of integrated post-management. Not that I'm aware of. The bigger, not so much, because the albumen is fermented and it's a very thin layer. But the bigger issue really are these gelatin prints that are nutrient for mold. Mold is your challenge. But not so much the fact that this is an animal product. Okay. We have a number of questions that are getting into sort of those treatment questions. And Heather, again, has been handling them pretty well. But I just want to run through a few of them and then you can add your sense. So Heather, taking nicotine off a photograph at the beginning of the presentation, and I'm guessing that that's a common problem, but one that most museum professionals should not undertake themselves if that's work for a conservator to do. Correct? Yes, that's correct. The conservation treatment of these materials is incredibly complex. You can only imagine, you think of the cross-section, the various processes that we just ran through today. There's so many more out there. And so first, you know, you need to be really certain that you know what this process is, whether you're dealing with a gelatin collodion or albumen binder layer. And then the condition certainly dictates how it might respond to various conservation treatment procedures. And a lot of this has to be tested under the microscope. You need to understand what that binder is and what sensitivity is. So when you're involved in doing something like removing nicotine from a surface, you have to identify a technique that will safely remove that product, whatever it might be, without damaging the binder layer or the image material. And it requires an awful lot of study, that photograph that Heather cleaned so beautifully that was hours and hours of work under the microscope to be sure that she could safely remove the nicotine and the dirt and discoloration from the surface without adversely affecting the gelatin binder, which tends to swell with exposure to moisture. There are a variety of different techniques that are used, but this very much is in the realm of the photograph conservator. And luckily, there are photograph conservators, regional centers, conservators in private practice, conservators who work in institutions who can help with this. Okay. And is it possible to reverse the mirroring effect that you have in your experience? Yeah, now that mirroring, again, is something that is... You can have mirroring whenever you have a silver-based image and a binder layer, but it's much more common with gelatin binders and much more common with silver gelatin developing out prints and also glass plate negatives. Those of you who have gelatin dry plate negatives in your collections may have an enormous amount of mirroring. It is a migration of the silver image. So this is a silver in the photograph that's migrating and being redeposited, reduced on the top surface to create that reflective sheen. There are techniques that can be used to minimize the mirroring through waxing and other coatings that are applied. Again, it must be done by photograph conservator because it's problematic and very difficult. But in some situations, just leave the mirroring. But in other situations, it is problematic. It makes it difficult to really appreciate the image because it's so highly reflective, particularly eliminating a lot of the detail in the dark. So there are techniques that can be used that are both physical and chemical. But again, like surface cleaning, it's something that should be done by photograph conservator. Okay, great. Anything can't be corrected by adding more silver or more salts to it. No. There are also chemical techniques that are much more aggressive that can be used to remove silver mirroring. So there's all different approaches. Again, to sort of think back on what's causing it, this is exposure to high relative humidity conditions that causes that gelatin to swell and then pollutants cardboard, poor quality boxes, pollutants in the air sort of enter into that gelatin matrix and begin to react with the silver image. Silver image is converted to ions. They migrate to the top surface of the gelatin and they're deposited there. The difficulty with removing mirroring and the reason we tend not to do that is that it is part of the original object. So you really have to think twice. And sometimes this is a patina that's appreciated. For example, I showed you very early on a railgram by Man Ray. Many of his photographs have mirrored, and that's really part of, that's accepted. And so you wouldn't want to intervene. And so you need to understand in these techniques, too, part of conservation is understanding the process, its deterioration, the methods and materials, ethical parameters, and artist intent as well. Great. Kalani had a great question about the paper. You said a lot of research was going into the different supports. Yeah. She wondered when the different kinds of non-fiber-based paper came into use. She's seen some modern silver prints that are sort of a plastic type. Yeah, that's a great question. You began to see the introduction of what we call resin-coated papers in the 1960s. I believe that's, I don't know the exact date. But during that time period, and this is simply a good quality paper support that's coated on both sides with a thin plastic layer of polyethylene. And therefore it's called resin-coated, because it's coated with this thin plastic layer on both sides. And this was done to minimize processing time because you could wash and fix these papers much more quickly. They didn't absorb the chemicals. They were perhaps a bit more permanent in that way. You could get a very nice, highly reflective surface. So you begin to see these in the 60s, and they really become very popular soon thereafter. So fiber-based paper, entirely fiber-based paper is early on. And you start to see the introduction of a variety of paper where you've got that paper coated with the barium sulfate and gelatin. And then ultimately in the 1960s, RC paper, resin-coated paper, or paper that's coated on both sides with polyethylene. What I should do, Kristen, probably, is move to finish up my next few slides since we're almost out of time, right? Yeah. Can we pick those up next time by chance? I was going to move to the homework slide. Yes, we can, because actually they are pretty much what you see here with just different images. So we can go ahead and move back to the homework so you can share that with everyone, and then I can pick it up, which would be a nice summary, actually, at the start of the next webinar. That would be fine. Okay. Thank you. So everyone, I've just pulled over the slide. It describes the homework, but the link is coming up right now on the screen. Cover up this lovely photo, but I did have... There was an interesting question. Oh, by the way, what is that photo? It's a cyanotype, right, because it's blue in color. Right. Okay, sorry. Well, the homework is just going to say, the homework is going to ask you to use the graphics atlas, which Debbie referenced a few times, and to use it to identify something in your collection, whether your personal collection or your institution's collection that you maybe aren't so sure about and see if the graphic atlas helps you out and then tell us more about the photograph. It's simply an interesting assignment. And then again, if you're watching with colleagues today, tell us who you're watching with, so we can give them credit for attendance. And if you're watching by yourself, we know who you are. We see you have logged in. You shared your name, so we don't need to hear that you're watching, but we're glad you did. Let's see if we can get a question or two before we wrap up. I guess Sarah picked up on collodion and having cellulose nitrate in it. Is that correct? Yes. No, it's not a hazard necessarily, but collodion is a form of cellulose nitrate. But when you're dealing with collodion prints, such as the Matt collodion photograph or the glossy collodion photograph, or even the tin type or the amber type in which collodion is a binder, the layer is so thin that it's really not hazardous. However, and that's a great question and a good preview to the next webinar. Which is going to focus on negatives. When you have a cellulose nitrate film negative, there you're dealing with much more cellulose nitrate and a different degree of nitration when compared to collodion. And that can be a hazard, but collodion as a binder layer is not necessarily hazardous. But it is important to just step back again and think, you know, what is collodion? That's cellulose nitrate. What is albumin, the white of hen's eggs? What is gelatin, a commercially prepared protein? So you sort of begin to understand these materials. Great. And we had a couple of questions today about slides and actually lantern slides. So that's coming up, correct? You know, I was reviewing this morning some of the questions and also the homework and the number you asked about lantern slides. So I thought I would add in information about that. What would be enormously helpful to me is if a few of you would send examples of some of your lantern slides or other problems that you're having. And remember, you also mentioned panoramic photographs. So if you send images to the Dropbox, I will put them into the talks and speak, you know, sort of from those images. Lantern slides are... Oh, go ahead. Oh, sorry. Well, you'll be also getting into storage, I think, in webinar four. So things like how to know when to separate an acidic mat or to take things out of acidic paper albums. Yes. I'm going to do that in webinar four. And what I'm thinking actually for webinar five, which I haven't put together yet and I'm holding off on, is, you know, to see what the questions are and part of webinar five will probably go into this in more detail. Again, for webinar five, what would be great is for you all to send images of some of your storage questions and problems, and we will just run through them and say, you know, in this case, you might do this or that. And much the same way I would do if I had you all in an auditorium because I'd have your images. So we will... That's a big issue, and we will talk about it in four and hopefully a bit in five as well. Great. How do we connect to the Dropbox? Uh-oh. Kristen, someone's asking that, and I don't know. We've shared, Heritage Preservation has a Gmail account, and that can handle some pretty big file sizes. So we just shared our Gmail address with you. So Heritage Preservation DC, all one word. The DC is important, at gmail.com. And we just shared that in the chat. So... Or if you want to send an email at info at Heritage Preservation, we can figure out a way to get larger files to us. I know we're running out of time. I think we are out of time, but I wanted to thank Heather for being online and answering these questions. And you all may be interested to know. So Heather is finishing up her second year study in our three-year program. Greta's finishing up her third year. And so both of them have been very involved in the development of this webinar. But for Heather, this is actually part of her final exam this semester, actually being online. And she's done a fabulous job. It's such a great example for her. It's such a great opportunity to really respond to, in real time, a wide variety of questions and problems. So thank you for your good questions throughout this webinar as well. Great. Well, we're at 233, so we're going to let you get back to work. And thank you so much for attending. Again, look for our email with links to come later today and check the course page for additional answers. I'm laughing because someone said we should give her an A. OK. OK. All right. Thank you guys. It's been fun. Don't forget, next time we're at a different time on the 16th, I think. Yeah. Our next class is Thursday, May 16th at 3 p.m. Eastern Time. Sorry to you folks in Europe who are making you stay up even later than you already do. But we really appreciate your participation. Thanks again, everyone. Have a good day. Thank you, guys.