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 4,864]

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 158]

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.

[Hulk 903]

Hi PD!

We're still waitin'! 

<bump>

[Fallonator 0]

On 10/31/2018 at 4:02 PM, PDWhite said:

Hello!

My name is Philip White. I was the manufacturer of the Stoker Electric Reduction Kiln. The company, a.k.a. The Reduction Production Refractory Factory was building Stoker Kilns in Amesbury,Massachusetts, USA. It had to close in the early 1980's when the US Small Business Administration reconsidered RPRF from being a 'small' business to a 'miniscule' one and not important enough to continue subsidizing. Consequently, the whole thing went down the tubes. Needless to say, I was so disillusioned with this state of affairs that I didn't want to have anything to do with kilns or pottery for years.

 

Flash forward to 2018 and I'm now retired. Thought I'd see if the Internet knew anything about the Stoker. I was amazed to see it mentioned on this website. Subsequently, I decided to come 'out of the shadows' and share a little of what I learned about electric reduction firing and the engineering constraints that made it highly doable and practical. Some of this may be surprising, and (I hope) edifying. Some of what I discovered, you may find surprising. As with other discoveries, it was under our nose all this time, but no one had connected the dots.

It is really not my intention to write a 'book' on this topic without knowing if there is still any interest.

If there is anyone that may find the subject interesting, or want to actually learn more and build one, please reply and perhaps we can open a thread on the subject.

Phil White

Im the Plumber from Fallonator.com I interested in talking Reduction in electric kilns.

send me a email

 

[Dick White 440]

On 10/17/2019 at 10:08 AM, Fallonator said:

Im the Plumber from Fallonator.com I interested in talking Reduction in electric kilns.

send me a email

 

As I noted in this thread back in Dec, Terry is The Man Behind The Fallonator.  Plumbing of the highest order meets pottery of the highest order!

dw

[Austin Paul Geithner 0]

 Is this thread still going?! I just got an Electric Reduction Production Kiln from a couple in Frederick, Maryland. It’s pretty beat up, but I’m going to repair it the best I can do I can use start using it again.

the wealth of information here is overwhelming, as I am a relatively new to ceramics especially gas and reduction firing.

I‘m a bit concerned of the dangers of CO and potential explosions. I want to make sure that I practice the art of reduction firing safely and properly. Any safety tips or other advice on how to get started?

[neilestrick 4,864]

10 hours ago, Austin Paul Geithner said:

I‘m a bit concerned of the dangers of CO and potential explosions. I want to make sure that I practice the art of reduction firing safely and properly. Any safety tips or other advice on how to get started?

How is the reduction created in your kiln?

[Bill Kielb 1,285]

12 hours ago, Austin Paul Geithner said:

I‘m a bit concerned of the dangers of CO and potential explosions. I want to make sure that I practice the art of reduction firing safely and properly. Any safety tips or other advice on how to get started?

CO (Carbon  monoxide) is very dangerous to human life but in fuel based reduction a necessity to get the reduction reaction. CO is not explosive, it is the end result of a very dirty (fuel rich) flame.  Folks who do reduction generally wait until approximately 1600 f degrees to go into early reduction. This is often called body reduction or clay body reduction before the glazes have begun to melt. So why 1600 degrees? Before one introduces excess gas into a kiln to produce a dirty flame they wait for the temperature of the kiln to be above the self ignition temperature of the fuel so as not to build up enough raw gas to reach the lower explosive limit  (LEL) of the gas.

So that’s a mouthful but .........only  still very basic reduction. Reduction in electrics can be had with fuel / carbon monoxide or in some cases  chemically with silicon carbide local reactions.

Reduction atmospheres in electric kilns tend to corrode elements aggressively so Neil’s question is spot on. Pictures  of your kiln will help determine how this reaction was being obtained.

Reduction firing is fairly simple and folks do it daily with great result yet it only affects a handful of metals with respect to color and carbon trapping is a thing decoratively as well.

Much has been said about reduction, most of it with elements of correctness but as you have likely noticed much of the information can be partially correct or perception based. IMO, This is a solid description of the process and a good start: https://ceramicartsnetwork.org/daily/firing-techniques/gas-kiln-firing/demystifying-the-reduction-firing-process/  From there fuel based safety, carbon monoxide safety, gas train safety are all things one ought to learn  when firing a gas kiln, especially in reduction. Again, these things are relatively simple unfortunately one can find good and not so good explanations so locating good credible reading material is a thing.

unfortunately much of the above is from 2018 / 2019

[Austin Paul Geithner 0]

15 hours ago, neilestrick said:

How is the reduction created in your kiln?

I haven’t fired this kiln yet. I will most likely convert this kiln to strictly gas fired. I’m not exactly sure how I will induce reduction yet. I’m still researching and have a lot of experimenting to look forward to.

[neilestrick 4,864]

2 hours ago, Austin Paul Geithner said:

I haven’t fired this kiln yet. I will most likely convert this kiln to strictly gas fired. I’m not exactly sure how I will induce reduction yet. I’m still researching and have a lot of experimenting to look forward to.

Is it a round toploader? If so, see THIS BLOG for good information on converting it.