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Electric Reduction Firing?


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#1 HAUKSBEE

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Posted 09 August 2010 - 10:34 AM

I am just returning to ceramics after a longish hiatus, and I recall hearing in the past of a method for doing reduction fire in an electric kiln. Does any know if this can really be done, or, is it a new 'urban legend'? Thanks.

#2 JBaymore

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Posted 09 August 2010 - 11:54 AM

I am just returning to ceramics after a longish hiatus, and I recall hearing in the past of a method for doing reduction fire in an electric kiln. Does any know if this can really be done, or, is it a new 'urban legend'? Thanks.


Hauksbee,

It certainly can be done. Some of the finest celadon on porcelains done by a couple of folks I know in Japan are fired in the middle of Tokyo in reduction electric kilns. It is very common in Japan... not so much here in the US.

Years ago there was a company here in the northeast called "Reduction Productions" than made "The Stoker"...... an commercial electric reduction kiln.

There are a couple of "caveats" when doing this though.

The first is the issue of ventilation. A reduction electric requires far more ventilation than an oxidizing electric kiln. There is a higher volume of effluent generated, and the toxicity of that effluent is significantly higher due to increased levels of stuff like CO (carbon monoxide). It is not the equivalent of venting a fuel fired kiln, becacuse you don't need to burn much in the way of combustables to create reducing conditions..... and not heat energy. But it is far more volume than the typical "out the window or wall kiln vent" system should try to handle. If there is any doubt as to the effectiveness of the exhaust system, a digital display CO meter should be kept in the kiln room to monitor the conditions.

The next issue is the potential impact on element life. Reducing conditions cause deterioration of the protective oxidized layer on the surface of the elements. So they do not last as long. This problem can be mitigated to a degree by coating the elements with something like ITC100 HT. But be aware that the qulaity of the application job is critical. It does not matter if 99.99999% of the element is effectively protected...... when it burns through in one spot.... it is dead.

Replaceing the elements more frequently is just a "cost of doing buisiness" if you want to fire reduction in an electric kiln. Compared to consturcting and ventilating a gas kiln........ replaceing a set of $150 elements every so often can actually be cheap. Build that cost into the pricing of the work.

One characteristic of the reduction electric kilns in japan is that the elements are heavier gauge than those typically found in the US. They are also often surface mounted ribbon type. Unless you can do the math yourself, contact someone like Euclids Elements and have them make up custom elements for your kiln that are a larger gauge wire. Be aware that those larger wire gauge welements still have to fit into the groves in the brickwork of your kliln though.

Then there is the even-ness of the circulation of the reducing gases in the kiln. You do want an active draft system on the kiln to get even results. You don;t need much flow, but you do need flow.

As to what to use to caus the reduction....... my friends use a wood firebox hooked to the electric kiln. You can also use a small propane burner. "The Stoker" used a sliding tray of charcoal briquettes inserted in the bottom.

Stay away from the old common suggestion of popping mothballs into the spy holes! Posted Image

best,

....................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#3 Seasoned Warrior

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Posted 10 August 2010 - 12:01 AM

Reduction firing is done in the absence of oxygen but has any one tried firing in a muffle furnace using other types of gasses? Saggar firing appears to come closest to the use of a muffle furnace but the atmosphere in saggars relys in the combustion of organic materials to use up the oxygen and uses some of the compnents of the smoke generated to color the object. Muffle furnaces are often used in heat treating metals and properties in the treated metal are changed by heating the metal in a controlled atmosphere by introducing gasses into the muffle.

#4 hansen

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Posted 10 August 2010 - 05:20 PM

I am just returning to ceramics after a longish hiatus, and I recall hearing in the past of a method for doing reduction fire in an electric kiln. Does any know if this can really be done, or, is it a new 'urban legend'? Thanks.


I think I have heard of making a fairly air tight sagger filled with chracoal & the work in it used in some kilns. Suggesting this for electric may pose some problems, but on a small scale in an older kiln it might be worth experimenting with. For glazed pieces, with front loading electrics, raku firing is possible, with post-fire reduction in either combustibles or water, but possibly dangerous. I hesitate to suggest either of these options, it's probably wiser to build a small updraft fired with propane for your reduction, and that also allows higher temperatures

h a n s e n



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#5 hansen

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Posted 10 August 2010 - 06:30 PM

Anyway, I know this has been asked for several times but I just made the connection. Here is how to convert an old electric kiln into a gas reduction kiln. You don't have to have an old electric however, just use soft brick, figure the top out somehow. Dimensions should be adjustable but pretty close to standard specifications. - hansen

http://www.jossresea...conversion.html



I am just returning to ceramics after a longish hiatus, and I recall hearing in the past of a method for doing reduction fire in an electric kiln. Does any know if this can really be done, or, is it a new 'urban legend'? Thanks.


I think I have heard of making a fairly air tight sagger filled with chracoal & the work in it used in some kilns. Suggesting this for electric may pose some problems, but on a small scale in an older kiln it might be worth experimenting with. For glazed pieces, with front loading electrics, raku firing is possible, with post-fire reduction in either combustibles or water, but possibly dangerous. I hesitate to suggest either of these options, it's probably wiser to build a small updraft fired with propane for your reduction, and that also allows higher temperatures

h a n s e n






h a n s e n
Stone House Studio, Alexandria, Virginia

americanpotter.blogspot.com
thesuddenschool.blogspot.com

#6 HAUKSBEE

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Posted 11 August 2010 - 12:15 PM

Anyway, I know this has been asked for several times but I just made the connection. Here is how to convert an old electric kiln into a gas reduction kiln. You don't have to have an old electric however, just use soft brick, figure the top out somehow. Dimensions should be adjustable but pretty close to standard specifications. - hansen

http://www.jossresea...conversion.html


Thanks for all the response. I have an Olympic gas kiln in the back yard (being hooked up as we speak) and an electric coming for the basement. Reading the comments here, I am pleased that I remembered correctly; it is possible in an electric. But as with so many instances of one style being jury-rigged to suit another purpose, there are too many caveats, especially if the electric is inside the house.

However; thank you greatly for the link to converting an old electric to gas. I've had an old one sitting behind the house and have intended to convert it to a raku kiln. I think this link is exactly what I need. Again, many thanks.

#7 Marcia Selsor

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Posted 12 August 2010 - 06:17 PM


I am just returning to ceramics after a longish hiatus, and I recall hearing in the past of a method for doing reduction fire in an electric kiln. Does any know if this can really be done, or, is it a new 'urban legend'? Thanks.


Hauksbee,

It certainly can be done. Some of the finest celadon on porcelains done by a couple of folks I know in Japan are fired in the middle of Tokyo in reduction electric kilns. It is very common in Japan... not so much here in the US.

Years ago there was a company here in the northeast called "Reduction Productions" than made "The Stoker"...... an commercial electric reduction kiln.

There are a couple of "caveats" when doing this though.

The first is the issue of ventilation. A reduction electric requires far more ventilation than an oxidizing electric kiln. There is a higher volume of effluent generated, and the toxicity of that effluent is significantly higher due to increased levels of stuff like CO (carbon monoxide). It is not the equivalent of venting a fuel fired kiln, becacuse you don't need to burn much in the way of combustables to create reducing conditions..... and not heat energy. But it is far more volume than the typical "out the window or wall kiln vent" system should try to handle. If there is any doubt as to the effectiveness of the exhaust system, a digital display CO meter should be kept in the kiln room to monitor the conditions.

The next issue is the potential impact on element life. Reducing conditions cause deterioration of the protective oxidized layer on the surface of the elements. So they do not last as long. This problem can be mitigated to a degree by coating the elements with something like ITC100 HT. But be aware that the qulaity of the application job is critical. It does not matter if 99.99999% of the element is effectively protected...... when it burns through in one spot.... it is dead.

Replaceing the elements more frequently is just a "cost of doing buisiness" if you want to fire reduction in an electric kiln. Compared to consturcting and ventilating a gas kiln........ replaceing a set of $150 elements every so often can actually be cheap. Build that cost into the pricing of the work.

One characteristic of the reduction electric kilns in japan is that the elements are heavier gauge than those typically found in the US. They are also often surface mounted ribbon type. Unless you can do the math yourself, contact someone like Euclids Elements and have them make up custom elements for your kiln that are a larger gauge wire. Be aware that those larger wire gauge welements still have to fit into the groves in the brickwork of your kliln though.

Then there is the even-ness of the circulation of the reducing gases in the kiln. You do want an active draft system on the kiln to get even results. You don;t need much flow, but you do need flow.

As to what to use to caus the reduction....... my friends use a wood firebox hooked to the electric kiln. You can also use a small propane burner. "The Stoker" used a sliding tray of charcoal briquettes inserted in the bottom.

Stay away from the old common suggestion of popping mothballs into the spy holes! Posted Image

best,

....................john



ITC 213 is the correct ITC for coating elements for protection in reduction. ITC 100 is used on bricks.
Marcia



#8 Marcia Selsor

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Posted 12 August 2010 - 06:22 PM

There was much discussion on Clayart about hybrid kilns. They use electricity for climbing the temperature and insert a little propane burner through a hole in the bottom of the kiln through the floor which will create a reduction atmosphere. The concern is to protect electic elements. This can be done by coating the elements with ITC 213 for metal coatings. Mel Jacobson recommended using a diluted bleach to clean the coating off the new elements, then dip the prepared elements in ITC 213 and let then dry. Check Clayarts archives for further details.

Marcia

#9 HAUKSBEE

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Posted 12 August 2010 - 09:02 PM

Thanks, Marcia. I'll check out Clayart.

#10 JBaymore

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Posted 13 August 2010 - 12:53 AM

Marcia,

I've used both.

best,

................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#11 Marcia Selsor

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Posted 17 August 2010 - 04:39 PM

Marcia,

I've used both.

best,

................john

How'd it work? I know people who have used it on lots of things from tile rack rods to pyrometers, burner tips, etc. I know Feriz, ITC inventor, recommends ITC 213 for metal.
M





#12 JBaymore

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Posted 17 August 2010 - 06:19 PM

Marcia,

The issue with any of the coatings on the elements is, as I noted above, that the old well known "weak link in the chain" theory applies here too. So any of the coatings has a serious Achilles Heel. That is the need for full and uninterupted coverage.

A single spot that has a scratch in the coating, an air bubble in the coating, or a tiny piece of the coating flakes off in the DIFFICULT job of installing the coils in the typical American electric kiln (that has grooves of some sort) and THAT is the place the element will fail first. It does not matter if the rest of the element is pristine Posted Image .

So the coating tend to exend the element life from the "change in resistance" standpoint a bit for sure, because the deterioration of the overall wire diameter is delayed because a lot of it IS protected. But the deterioration of that single point with the missing coating eventually ups the resistance value of the element due it it becoming narrowed in conductive mass ... it is the "restrictor plate" in the system to electron flow........ and then that high resistance spot gets hotter than the rest of the element, and poof... it burns through there.

Do the coatings improve the situation... yes, a bit. Both work OK. They are NOT miracles however. I have found the same in using the coatings on new IFB construction for protection form soda also. Makes things a bit better... but again, not a "miracle cure for all ills".

One thing the ITC coatings do VERY well is increase the emmissivity of the surface of IFB. That causes heat energy to get re-radiated off of the wall surfaces much like light off of a mirrror. This tends to make the kiln fire more efficiently as more energy is absorbed by the wares themselves, and it evens out small micro-climates that can occur in any kiln.

It is pretty amazing how many firings a good Kanthal A-1 element will get with no protection added when used in enough reduction to get celadons and copper reds. So I am not really sure of the eventual payback on the coatings for the cost of the mateials combined with the cost of your labor time to do the coatings "to spec".

As I said above, I'd just figure in the cost of replacing elements every X firing into the cost of the reduction fired pieces. A cost of doing business. Simple.

There are TONS of reduction electric kilns in use in Japan... and they typically use NO coatings on the elements at all. The old "Reduction Productions" Stoker kiln made here in the US used no coatings on the elements, just a heavy guage A-1 Kanthal element.



best,

...............john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#13 Marcia Selsor

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Posted 18 August 2010 - 05:27 PM

Thanks John. I remember using glo-bars electrics in grad school. Someone loaded a kiln full of bricks (solid mass) and burned them out. I imagine that those would survive well in reduction.
Have you ever seen Beatrice Wood in "Mama of Dada" ? In it she is putting wood into her electric kiln for a luster firing.
So as there are no silver bullets, I agree that ITC 100 does seem to improve firing with a coating on the IFB. I have sprayed it onto my fiber raku kiln too. It helped but the fiber did eventually shed the ITC 100.

After 40+ years, the longer I work with clay...the less I feel anything is certain. Just had a glaze screw up. Not sure if I put a mislabled chemical it the glaze or what?...moved them all from Montana or what has happened.

Thanks,
Marcia

#14 High Bridge Pottery

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Posted 15 November 2013 - 09:14 AM

This guys video was interesting.

http://www.youtube.c...h?v=tGQLp92XwNQ






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