this weekPaper or Plastic

May 6, 2005

The Wet Collodion Process

Developing a better negative

Intellectual-property lawsuits may seem like a thoroughly modern phenomenon, but the struggle to assert one’s rights over a creative work is very, very old. Patents, copyrights, and other formal claims of authorship exist largely—in theory, at least—to guarantee that a work’s originator has the greatest opportunity to profit from it. But ethical and legal complications arise when more than one person claims to have created something first, when the scope of someone’s claim is unclear, or when a creator’s interests are potentially at odds with the public good. The outcomes of such cases (one way or the other) can have a profound impact on technological progress, not to mention the financial success of both individuals and entire companies.

In the mid-1800s, a grand battle took place between a patent holder and someone who we might today call an open-source advocate. As it turned out, both sides lost, but the public gained. The technology under dispute was nothing less than a method for creating multiple, clear copies of a photograph from an original—something we take for granted today, and without which, the world of media would be very different.

Picture Imperfect
The earliest days of photography were both exciting and frustrating. The daguerreotype, for instance, invented in 1837, made a beautiful, sharp image on a copper plate coated with light-sensitive silver iodide. But creating just one picture required extensive preparation, an exposure as long as 20 minutes, and development using toxic mercury vapors. Because the end result was a positive image on metal, there was no way to make a copy.

A less-expensive, competing process called the calotype was patented in 1841 by William Henry Fox Talbot. A calotype began with a negative image printed on light-sensitive paper. To make a positive, one sandwiched the negative together with a second sheet of the paper and exposed it to the sun. Because Talbot’s process was repeatable, one could make numerous copies of a single image. But the images weren’t very sharp, because the irregularities in the paper itself caused distortions; calotypes also took much longer to create.

Holy Colliding Colloids!
Frederick Scott Archer was an English sculptor who liked the idea of working from a photographic image of his subjects. But the limitations of both daguerreotypes and calotypes made them less than ideal for his work, so he set about to create a solution—a process with all the sharpness and contrast of the former and the reproducibility of the latter. In 1848, he struck upon the idea of using a recently invented substance called collodion.

Collodion is a thick, sticky, clear, gelatinous substance. To make it, you start with pyroxylin—also known as “gun cotton”—which is created by treating cotton or wood pulp with nitric and sulfuric acids. Dissolve the pyroxylin in ether with a small amount of alcohol, and it turns into an adhesive of sorts. (The Greek word from which collodion is derived means “glue”; the same root gives us the word colloid, any of a class of gelatinous substances of which collodion is just one example.) At that time, collodion was used primarily to dress wounds. Archer’s innovation was to coat a glass plate with a mixture of collodion and potassium iodide, and then dip the plate into a silver nitrate solution to make it light-sensitive. (In fact, it was very sensitive—exposures could now be as brief as a few seconds.) Because the plate had to be placed in a camera, exposed, and developed immediately—while the coating was still wet—Archer’s method was known as the “wet collodion process” (or, sometimes, the “wet plate collodion process”). The result was a sharp, durable, glass negative that could be used to make any number of prints. In other words, it was a direct ancestor of modern negatives.

Nice Guys Finish Last?
Archer did not patent his process, but instead published a detailed description in the March, 1851 edition of The Chemist—making it freely available to all comers. It was an immediate success. Almost overnight, the daguerreotype and the calotype became obsolete; the wet collodion process went on to dominate photography for nearly 30 years. Although later discoveries would eliminate the awkward need to work with wet plates, Archer’s invention opened entirely new doors for the young art of photography.

One person, however, was highly chagrined at this turn of events: William Talbot. Talbot held that his calotype patent covered all silver-based photographic processes, and that therefore anyone who used Archer’s wet collodion process owed Talbot a licensing fee. For three years, Talbot waged intense legal battles, driving some photographers out of business. This made him an extraordinarily unpopular figure in the photographic world, and eventually the courts ruled that those who used Archer’s process were not in fact violating Talbot’s patent. So Talbot lost, but so did Archer. Because he didn’t patent his own process, he earned virtually nothing for his efforts. When he died in 1857—at which point his invention was still just taking off—he was penniless.

This little tale does not have a nice, neat moral. We want to be thankful to Archer for his selflessness while at the same time lamenting his foolish lack of foresight; we feel angry at Talbot for being mean-spirited and vindictive, while respecting his prudent choice to patent his invention. So I suppose the lesson I take away is: “Be smart, but also be reasonable.” —Joe Kissell

More Information about The Wet Collodion Process…

To learn more about Archer and his wet collodion process, see: