Using protectants for soda firing in a converted gas kiln w/soft bricks

[ATauer]

After getting a great deal on an Olympic oval that is quite a bit bigger than the Skutt KS-1227-3 that I got for free, I decided to convert my Skutt into a gas kiln ala Simon Leach (yes, I know there are some issues with the conversion that people have brought up in previous threads, I will be using a regulator on my burner and babysitting the kiln at all times, and I  have dozens of reasons for doing this) which will save me about $1000 on the things I would need to do to make the Skutt workable as an electric kiln. I have recently become interested in light soda firing while learning about doing soda firing with raku, which I know is quite a bit different at low temperatures. I know that soda or salt will tear up soft kiln bricks, but I have found out about several sealants you can put on the bricks that are supposed to protect the bricks, at least for a time, from the soda. I would not be doing heavy soda firing, as I rarely like the colors in heavy soda firings especially if the work doesn’t have any other coloring/glazes, so I’m mostly interested in light soda that adds a light glaze to the work and the particular kind of sheen that that work has, with the occasional flashing. This would not be something I would do a huge amount of, I am more interested in a handful of reduction glazes that I’m obsessed with enough to want to be able to do reduction (and not just silicon carbide reduction, something I enjoy experimenting with in my Olympic kiln as well, but want the ability to do the real thing sometimes) and I would also be firing the gas kiln in neutral/oxidation plenty when I have a long glass casting project going in the Olympic kiln. I realize once you put salt/soda in a kiln it is forever a soda kiln, as it has the soda in the bricks that can react later, but if it is only lightly used, and I put the protective  covering on as frequently as it is possible to use it…well I’m just wondering if anyone has experience with these products with the soft brick kilns and soda kilns, especially if the soda firings are very infrequent. If everything points to it being a terrible horrible idea, I will resign myself to doing soda/borax fuming reduction in raku, and possibly use the soda kilns at some other places when I have the opportunity (they just tend to do them heavier than I like).  Thank you. 

[Bill Kielb]

My experience, coating the walls works and slows down the degradation. The kiln walls will accumulate soda as the kiln becomes seasoned. The walls will continue to degrade ……. As will the shelves. So each and every subsequent firing will be influenced by the soda and the bricks will degrade. Coatings do protect or slow this degradation down but coatings do not prevent accumulation or eliminate it.

Its hard to use one kiln and go back and forth from soda to non soda use. As for light soda, have you thought how you will apply the soda?  Light uniform applications are hard to come by.

The influence on your regular firings, the accumulation, constant degradation will probably make this soda only in relatively short order IMO.

[ATauer]

On 4/5/2022 at 3:44 AM, Bill Kielb said:

My experience, coating the walls works and slows down the degradation. The kiln walls will accumulate soda as the kiln becomes seasoned. The walls will continue to degrade ……. As will the shelves. So each and every subsequent firing will be influenced by the soda and the bricks will degrade. Coatings do protect or slow this degradation down but coatings do not prevent accumulation or eliminate it.

Its hard to use one kiln and go back and forth from soda to non soda use. As for light soda, have you thought how you will apply the soda?  Light uniform applications are hard to come by.

The influence on your regular firings, the accumulation, constant degradation will probably make this soda only in relatively short order IMO.

Thank you for the insight. I was planning on either wrapping the soda ash up in newspaper and giving it a quick soak in water before putting it in at the bottom close to the burner port, or since I will be buying a couple of the garden sprayers with long metal tips for use with raku to open the lid briefly to spray as uniformly as I can…the trouble being that I will be using more than one kiln shelf of ware, so I may have to go in the peeps instead, on both sides instead, as from above I will not be able to get at the lower shelves very well. 

If it will become a soda kiln only pretty quickly, I would prefer not to have that happen, but I have a third kiln laying around (crazy, considering how it wasn’t too long ago I thought it would be years and years before I would ever have my own kiln. It is useless as an electric kiln for pottery other than for luster, as it will only go up to 1800*F, and I had planned on using it for smaller glass projects by building my own electronic controller, which I am still on the fence for, but most recently I had been thinking of using it as a second, smaller raku kiln or even just as a post-fire reduction chamber. That or selling/giving it away. But perhaps, if I’m doing raku and converting a bigger kiln to a gas kiln, it wouldn’t be much bother to convert this as a second gas firing kiln and reserve it for soda. But it is so small, only 18 in tall on the inside, about the size of a large dinner plate in diameter inside, I don’t see how I could fit the downdraft conversion in it and have room for even a small shelf,  and I would either have to be running it all the time to make it worthwhile doing soda, which would soak up my time since I can’t leave it while the gas is going for safety reasons, or I’d do it so infrequently that it would be better used in the other ways.

Perhaps I should have some patience, content myself with what I can do with soda in my raku kiln, even if it is not the same as high fire soda, and see what the universe brings my way…I never would have imagined that in short order I’ll have 4 kilns (counting the raku kiln I am building) taking up space in my unattached garage, so who knows what may happen. But I definitely need to be able to use the Skutt conversion for gas oxidation/neutral firings as well as reduction firings, so having it only be a soda kiln is not an option for me, so I should probably drop the idea for now. Thank you very much. 

[Mark C.]

I have converted same type of kiln to a salt kiln-one fire at it was salt forever which was not that many fires on it before death. I did this for an art center as a project-not sure how many fires they got out of it but less than 5 I'm sure

Soda is less corrosive than salt but very soon its a soda only kiln with a shorter life

[neilestrick]

Once a soda kiln always a soda kiln. Coatings will help to some degree, but it will get in to any little exposed crack and eat away at the bricks from behind. It may last for quite a while, though. We had an old Alpine updraft gas kiln in college that we converted to a salt kiln, and it appeared that the coating was working well, but then big holes would appear, the salt having eaten away the bricks from behind the coating. Those bricks were in pretty rough shape to start with, though, and it was fired quite a bit.  I say if you've got the money and the time, go for it. It'll be fun until it dies.