Better Kiln Wash and Wadding Recipe
After last weeks article about loading the soda kiln I received a few questions about kiln wash and wadding. Instead of answering each one individually I thought I’d just answer them all here. Feel free to add any other questions or information in the comments.
Kiln Wash is basically a combination of Alumina Hydrate, EPK, and water. Potters paint this on the kiln shelves to help prevent pots from sticking too the shelves. If glaze runs while the kiln is firing it can bond to the kiln shelf just like it bonds to the pots. Alumina Hydrate is highly refractory which, in simple terms, means it helps to prevent the bonding from happening. For a more scientific explanation of a refractory see the “Other Stuff” section below.
Wadding is made of the exact same ingredients as kiln wash but with much less water so it’s more of the consistency of clay. It’s got the same refractory properties as the kiln wash but it is usually only used in atmospheric firings where something is added to the atmosphere of the kiln that will create a glaze (wood, salt, and/or soda). Since the glaze is created by introducing something to the atmosphere it tends to glaze everything in its path so we put small pieces of wadding under the pots to prevent them from sticking to the kiln shelves. This allows the glaze to flow under the pot also so you can get an almost fully glazed piece. Since the glaze doesn’t land on the pot wherever the wadding is some potters use it to help create beautiful design effects. Some potters will add combustibles like sawdust or coffee to wadding often for esthetic reasons.
When I was at Penland School of Crafts we used Cynthia Bringle’s recipe for wadding and kiln wash. The recipe uses less Alumina Hydrate, the more expensive ingredient, therefore it costs a little less to make. We fired about 2000 glazed pots in many salt and soda kilns. I promise it works just as well as the 50/50 mixture I’ve always used.
Kiln Wash and Wadding Recipe:
70% EPK
30% Alumina Hydrate
Enough water to make it the consistency of the application you desire. If you use too much water it can be dried out via evaporation or on plaster.
Other Stuff:
Definition of Refractory - https://en.wikipedia.org/wiki/Refractory
Alumina Hydrate - http://dictionary.reference.com/browse/aluminum+hydrate
Edgar Plastic Kaolin and other raw materials - http://lakesidepottery.com/HTML%20Text/Tips/Glossary%20of%20Ceramic%20Raw%20Materials.htm
Check out the gallery page - Future Relics Gallery by Lori Buff
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| Pots in a Salt Kiln (wadding is circled) |
Wadding is made of the exact same ingredients as kiln wash but with much less water so it’s more of the consistency of clay. It’s got the same refractory properties as the kiln wash but it is usually only used in atmospheric firings where something is added to the atmosphere of the kiln that will create a glaze (wood, salt, and/or soda). Since the glaze is created by introducing something to the atmosphere it tends to glaze everything in its path so we put small pieces of wadding under the pots to prevent them from sticking to the kiln shelves. This allows the glaze to flow under the pot also so you can get an almost fully glazed piece. Since the glaze doesn’t land on the pot wherever the wadding is some potters use it to help create beautiful design effects. Some potters will add combustibles like sawdust or coffee to wadding often for esthetic reasons.
When I was at Penland School of Crafts we used Cynthia Bringle’s recipe for wadding and kiln wash. The recipe uses less Alumina Hydrate, the more expensive ingredient, therefore it costs a little less to make. We fired about 2000 glazed pots in many salt and soda kilns. I promise it works just as well as the 50/50 mixture I’ve always used.
Kiln Wash and Wadding Recipe:
70% EPK
30% Alumina Hydrate
Enough water to make it the consistency of the application you desire. If you use too much water it can be dried out via evaporation or on plaster.
Other Stuff:
Definition of Refractory - https://en.wikipedia.org/wiki/Refractory
Alumina Hydrate - http://dictionary.reference.com/browse/aluminum+hydrate
Edgar Plastic Kaolin and other raw materials - http://lakesidepottery.com/HTML%20Text/Tips/Glossary%20of%20Ceramic%20Raw%20Materials.htm
Check out the gallery page - Future Relics Gallery by Lori Buff
there is so much I don't know about all the chemicals; I learn every day, great post
ReplyDeletewow, those pots were packed in extra tight weren't they?
ReplyDeleteThat is basically the recipe we use for wadding too. We have fired with a few people who add sawdust or flour to the mix. I really don't like it. The wads seem harder to take off and they often leave speckles instead of white dots on the bottoms of pots.
ReplyDeleteI do 1 part alumina hydrate, 1 part kaolin, 1 part coffee grounds. Makes the wadding softer so it grinds away more easily...you know I love those rivers of soda!
ReplyDeleteI’ve heard of people doing that and may try it sometime. It’s a good way to get rid of those used coffee grounds and the wadding should smell good.
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