There are several firing methods in ceramics: electric, gas, vapor, pit, wood, and a few others. In the very recent past, I’ve fired in an electric kiln because this is the equipment that I own and operate in my home studio. I have had my work fired in a gas kiln while I was in college, but never actually operated the kiln myself. Last weekend, I had the opportunity to participate in a gas kiln firing at the Colorado Potter’s Guild where I am a new member. The guild acquired a new 25 cu. ft. Cooperworks gas car kiln last summer and many of the members are hesitant to fire it. Let’s face it, we’re all creatures of habit - myself included.
I showed up for the workshop because I want to be able to learn how to fire it myself without having to depend on others to fire my work for me - though I’ll be hard pressed to fill a 25 cu’ kiln myself at the rate I produce work. If the firing isn’t quite as expected, I will have no one to blame but myself. Not knowing a ton about gas firing, I’ve decided to learn all I can about this method of firing. Yep - the same geek who was hell bent on hosting my own blog and setting up my own website also wants to KNOW how to use the gas kiln successfully.
For those of you who are not ceramic people, gas firing is desirable because you can get different effects from a reduction environment. When I say reduction - I’m referring to an atmosphere that is deprived of oxygen (though gas kilns can also be fired in oxidation). Electric kilns have an oxygen atmosphere, hence the term “firing in oxidation”. What does this mean? Each firing method produces different results. For example copper can turn red in a gas firing - whereas, it will turn green in an electric kiln.
This past weekend, we fired the “Coop” to ^10 and experimented with different reduction times and temperatures. For those of you unfamiliar with the symbol ^ or the term cones - it refers to the temperature to which the kiln is fired. ^10 is approximately 2340° F. Want to see the cone chart? Click here. When I fire my electric kiln, I fire to ^6 or approximately 2232° F. 100+ ° F doesn’t seem like a lot, but it affects how a glaze melts - so when ceramic people are searching for glaze recipes, they’re also looking at the ^ of a recipe in order to achieve successful results. Firing at a lower temperature is also more economical. On a side note, potters are taking note of our consumption of natural resources - there are groups who are firing their kilns using geo-thermal energy and I am eventually going to try going solar for my electric kiln in my own studio.
So what am I currently reading? The Complete Guide to High-Fire Glazes by John Britt and a classic, Kilns: Design, Construction, and Operation by Daniel Rhodes.
I only added 3 pots to the guild firing and was rather unimpressed with the results. Not being familiar with the guild’s glazes, I used my usual application method and dipping time. Turns out, I need to dip the pots longer than my usual 3 second dip time according to one of the other members - my application was too thin. Now I know - but will share my results nonetheless:
The first 2 images are the same bowl - glazed with a tenmoku glaze. The 3rd and 4th images are the same bowl - glazed with ohata khaki (a gorgeous iron red). The interior is beautiful - but the exterior crawled terribly. I washed my original glaze choice off the bowl the same day as the firing and didn’t allow enough time to dry completely before glazing again. The 5th image is a celadon, which should be more green/blue. The bowl had too thin of an application of glaze and the result is a pale olive green glaze. It also had some kiln shelf debris that fell into it. Good thing the glaze turned out so poorly.
Even mistakes are good learning opportunities. I signed up to fire the kiln in late April with 2 other potters, so hopefully, I’ll have a little more success the next time. In the meantime, it’s a beautiful day - so I’m heading out to the studio as soon as I’ve signed off.
Have a great weekend,
~Cynthia
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I love the interior and exterior glazes combined, just beautiful, sometimes mistakes are the best thing to happen to a piece. Can you do it again? I love the way the shapes are outlined, the movement, texture and variation of earthy colors.
I remember back when I took ceramics in college that I loved using tenmoku glaze. I still have a couple of rice bowls I made using it, and a raku tea bowl (raku was so much fun). I loved celadon too, especially on white clay - there’s nothing like that particular pale green. It always reminds me of the sea. I also remember that being one of the great things about ceramics - it’s so much about the process, learning from mistakes as well as successes. Maybe if I’d gone further with it, I would have felt more stress about the final product, but for the 2 quarters I studied it, I found the process of making ceramics so relaxing.
Good for you for looking into alternative energy sources for powering your kiln, too.
I always learn a lot when I read about the pottery stuff. Of course, since I’m starting out not knowing anything that is pretty easy, still I like the processes you show and tell us about. Thanks, and guess who is going to take an HTML class! Yeah, moi!
Hey Marcia - I don’t want the crawling to happen again, but I just loved the interior of the ohata kaki glaze.
I knew after taking my first clay class - maybe even before that, that I would love working with clay Angela. It’s seductive…well at least to me.
Good for you Mary - I took a few online html classes last spring (or maybe it was the spring before last) that were really beneficial to getting a better handle on my blog.
Am so glad you are up and running !!!
The Ohata Glaze is a winner as is the fluted bowl !!! It sounds like they are studio glazes. Do they share the recipe with you?
Recently (a couple of days ago) Out of the Earth, Into the Fire by Obstler arrived so have been busy reading . . .
It’s GREAT that you’re having the opportunity to work with folks that know how to run a gas kiln. Mine is sitting out in the kiln room which is still buried with snow. As soon as we have 12 hours of sunlight, am going to dig a tunnel to it — but i still don’t know how to run the durn thing!
Happy Glazing
Hugs
Chae
I love the effect and the sound of gas kiln. I get mesmerized when I raku fire, especially the roar of the kiln during reduction. The travelers say I`m a frustrated chemist with an odd fire fetish.
Your site looks really good Cynthia.
Chae - the ohata is a studio glaze at the potter’s guild - I’m sure they have a recipe file. I think the best way to learn how to do something sometimes is to just do it!
I was pretty mesmerized myself, John - it felt so mysterious. I feel really fortunate to have access to a gas kiln now. I’ve never been a raku firing fan - but for the same reason that I don’t like to be the one manning the camp fire. But, I love raku!
I don’t have a lot of experience with it…but I can say that a reduction firing is very much like Christmas. The kiln bequeaths its’ presents. They are unpredictable as can be. That’s part of the mystery and the wonder. I love it, myself.
Very nice site, Cynthia.
Welcome, Becky! You’re right it is a bit of a surprise and like my birthday looking in the kiln.
Now you’re cooking with gas!
Hi, I have recently came into possesion of a gas kiln and yes it is like christmas everytime it is unloaded, I do a lot of reduction fires and everytime I come to love it more. I have never worked with glazes instead choosing to work with oxides. I am going to today fire my very first all glazed works. That is how I found this site..Thanks for your comments. Enjoy that new gas kiln…There is nothing like it!
Michelle