Tuesday, October 21, 2008

Firing your own pottery, You Brave Soul

Careful. It's addicting.

So, you've acquired a kiln from Great Aunt Minnie who made the cutest little Christmas trees and poodle figurines, and you'd like to try your hand at moving and firing the earth. Electric kilns are not rocket science, and you can learn to fire one, but safety is very important since you're playing with a couple thousand degrees, and the potential of getting zapped severely. Also, kiln fumes can be toxic, and glaze chemicals can be poisonous..Oh, and then there's silicosis from overexposure to clay dust... (Still with me?) This isn't to scare you off, it's just to let you know that there are pretty important things to know concerning life, limb, and clay.

While I am not an expert on the whole safety thing, I can get you started on the quest for kiln safety. The good news is, the subject is very searchable online- here's a decent basic discussion to get you off and searching: http://pottery.about.com/od/safetyinceramics/tp/kilnsafe.htm

Also, get an electrician to install your kiln- preferably not in the house. If your kiln is used, many manufacturers have owner's manuals either online, or they will send you one. Just contact them with the model and serial # on your kiln. There is usually a plate on the outside jacket of the kiln with this information.

Ok- assuming you've gotten your kiln safely installed, and you've made a few pots, let's bisque!

Bisque is fired clay without glaze. Generally, you do this first firing because it makes the ware strong enough to handle while you are glazing. Also, it is a low firing, so that the clay is porous enough to absorb your glaze. Be sure your pots are completely, totally dry. Moisture in the clay, especially if it's thick (kids love to build thick) will blow up. It's really not the air bubbles, it's the wet. kaboom! A good rule of thumb is this- if the clay feels cool to the touch, it's probably slightly wet. Touch it to your cheek- if it's as cool as you are, wait.

What is all this stuff I got with my kiln, and what do I do with it? : shelves, stilts, kiln wash, cones. The round or hexagonal things you got with your kiln are shelves.
The.... well, "stilty" things you got, usually a few different heights, are stilts.
Kiln wash usually comes in powdered form, and you add water until it's like cream, and paint it on ONE SIDE of each shelf. This helps you to remove glaze runs and drips without ruining the shelf. Important.
Here is an explanation of what cones are and what they do.
Can we load yet? Ok, here we go. The pic of the shelves and stilts is great because it sort of shows them in action. Start with some really short stilts and a full shelf at the bottom of your kiln. You want to raise the first layer of pots up to the first row of elements (those twisty coiled wire things all around the kiln.) Also, it's good to put your bottom layer of ware on a shelf, because you want to protect the bottom of the kiln from glaze drips. (when we get that far.)
Next, choose stilts that are higher than your tallest pot. Stack a couple of stilts if need be. Three stilts to each shelf will support it well. Y'know, the tripod thing. Add shelves, more ware and stilts- also add a conepack in at least one place in the kiln- near a peephole is good so you can check your firing, and stop the kiln if you must before the kiln sitter trips.
KILN SITTER?? What? - It's the thing sticking out of the side of your kiln. Inside, there's a porcelain tube, and some prongs. You'll put a small cone on the prongs. Outside, there's a lever that falls to shut off the kiln when the cone melts. Read more here.
Finally, my friends, (do I sound like McCain?) at long last, it's time to fire the dang thing. Close the lid- or, prop it open a little if you're afraid your ware might not be completely dry.
I'm going to assume that Aunt Minnie's kiln is older, and it has switches-not a computer controller (whole'nother article.) These switches work pretty much like a stove. Here is a good, conservative schedule to follow when firing a bisque. Follow the article to the bottom. Basically, it's low for an hour, then gradually turn the thing up over the next few hours until you are on high. The kiln sitter should shut off your kiln, providing you have it adjusted right, at the right temp. A bisque should take anywhere from 8-10 hours, depending on how slow you go and how old / worn your elements are. Any longer and there's a problem with the kiln- a discussion for another time.
Let the thing cool for at least a day- then open, unload, and start thinking about glaze!
So, if after reading this, you're thinking "the kiln gods aren't welcome at my house," -fear not! Join a local art center, audit a college class, or pay a potter (in NE Ohio, that would be me) and leave it up to the crazy people.
Questions? I'm sure there's something I didn't cover, so comment here or email me at sheaclaypottery@gmail.com

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