Electric Reduction Firing

[PDWhite 8]

48 minutes ago, neilestrick said:

46 minutes ago, neilestrick said:

So that's different than firing in reduction. More like what we call reduction cooling. Firing like the Fallon would not reduce the clay body. No reason you couldn't use his system to reduce going up, though.

My original experience with reduction firing was through the use of gas kilns. The one in my studio was a walk-in catenary kiln. (I loved it.) 

Since the gas being introduced into the kiln was for the purpose of heating it, cutting back on air going into the kiln, usually by closing the chimney damper slightly resulted in incomplete burning and brought about the reducing atmosphere. However, less burning of gas also meant less heat and so the kiln would not climb as fast, this is what's commonly understood as reduction cooling. The slowdown also allowed the now-fluxing glazes to melt, and the reduction atmosphere had time to pull out the oxidation.  On the other hand, attempting to reduce too strongly could cut the heat and stall the kiln. (Not too mention the production of dangerous carbon monoxide.)

[neilestrick 3,113]

31 minutes ago, PDWhite said:

My original experience with reduction firing was through the use of gas kilns. The one in my studio was a walk-in catenary kiln. (I loved it.) 

Since the gas being introduced into the kiln was for the purpose of heating it, cutting back on air going into the kiln, usually by closing the chimney damper slightly resulted in incomplete burning and brought about the reducing atmosphere. However, less burning of gas also meant less heat and so the kiln would not climb as fast, this is what's commonly understood as reduction cooling. The slowdown also allowed the now-fluxing glazes to melt, and the reduction atmosphere had time to pull out the oxidation.  On the other hand, attempting to reduce too strongly could cut the heat and stall the kiln. (Not too mention the production of dangerous carbon monoxide.)

I've only ever heard reduction cooling to mean reducing during the actual cooling cycle, not heating slower. Yet another confusion bit of terminology in the ceramics world.  So what would you call maintaining a reduction atmosphere during the cool down?

[PDWhite 8]

5 hours ago, neilestrick said:

I've only ever heard reduction cooling to mean reducing during the actual cooling cycle, not heating slower. Yet another confusion bit of terminology in the ceramics world.  So what would you call maintaining a reduction atmosphere during the cool down? 

Actually I've heard it referred to loosely both ways. What I termed as slowing the firing by closing the damper a bit, and forcing the atmosphere to become a reducing one is often referred to as a soak.  On the other hand, it takes a  very tight kiln to maintain a reduction atmosphere once the burners are shut off. Generally, fire brick kilns aren't tight enough to the atmosphere keep them from re-oxidizing fairly soon after the firing is over.

Most usually, it is the re-oxidation that occurs after firing which brings up the warm colors from the reduced glaze and clay bodies.

The Stoker kiln was built very tight and well insulated  in order to make the most out of doing a reduction with only a small amount of carbon from the charcoal briquettes it used. As such, it was possible to leave the briquettes in after shutting the kiln down, resulting in a non-oxidizing cool down. Doing so would often leave the clay and glazes without the warmer tones or re-oxidation, but did make it much easier to do copper reds and celadons.

Actually, I discovered that for myself accidently, by botching the first public demonstration of a Stoker kiln firing in New York City back in the '70s... But that's another story...

Edited December 6, 2018 by PDWhite
More readable...

[docweathers 148]

I asked Skutt how I might implement a Fallonator configuration with my 1227. This is what they said:

 

"Hello Lawrence,

We do not recommend introducing fuel into the chamber of an electric kiln.  It can be quite dangerous to do so.  In the case of the Fallonator it looks like you are depending on CO2 to displace any fresh oxygen in the kiln to prevent combustion, but if that CO2 fails to do its job you are turning the kiln into a big explosive container.  The heating elements get well beyond the temperature needed to ignite the propane.  I would recommend looking into Steven Hill's electric firing process.  He is able to emulate the look of an atmospheric firing through spraying his glazes and firing very slow without bisquing the pots (once firing).  This would be a much safer way to get the look of a gas fired piece.  Here are some links to his articles:

https://static1.squarespace.com/static/555a4afbe4b06f6e6f42474f/t/55712bc7e4b0334e5889b742/1433480135766/An+Approach+to+Single+Firing.pdf

http://www.stevenhillpottery.com/articles/

Generally speaking, introducing gas into an electric kiln chamber will deteriorate the elements and the brick, but it also has a chance of combusting.  I would not recommend putting any sort of gas in your kiln.  You may also be interested in asking around your community for access to a gas, salt, soda, or wood kiln.  Wood kilns are a lot of fun!!"

Edited December 7, 2018 by docweathers

[PDWhite 8]

Quote

Re:  Generally speaking, introducing gas into an electric kiln chamber will deteriorate the elements and the brick, but it also has a chance of combusting.  I would not recommend putting any sort of gas in your kiln.  

This is nothing new from Skutt or most of the other  small, portable kiln manufacturers.  I am sorry that I don't currently have time to  address the fallacies (and the  unsaid facts) in this statement right now, but I'm about to get to the part that explains the confusion involved with statements like these in the next installment on why reduction firing in an electric kiln is  possible and practical.  However,  this is not true for just any electric kiln. 

More on this topic when I have a bit more time to compose it.