soda firing Soda firing in ceramic fibre kiln?

[Twitchy]

Has anyone tried using a ceramic fibre kiln for soda firing by coating the fibre with a high-zirconia coating (such as "Furnascote") to protect it from erosion. The coating would still erode, but it might do so sufficiently slowly to protect the fibre, though it would need to be reapplied from time to time. Any comments, especially any actual experience?

Edited February 15 by Twitchy

[PeterH]

In case it's of interest-  googling  site:community.ceramicartsdaily.org fibre  soda firing
threw up some hits including

... which includes
In the 90's I decided to do a couple of soda firings in my ancient, Geil, fiber kiln. It sprayed the interior with ITC 100 and after just a couple of firings the old fiber just wouldn't stay put with the ITC. If you're looking for light construction you might try using IFB's, and coating 5 sides of interior bricks with the ITC 100.

 

... which uses fibre as a short-lived sacrificial liner

Elsewhere I found this thread

... which includes this post

 

[neilestrick]

Those coatings may be beneficial in a typical reduction firing because they harden the surface of the fiber and make it more durable, but in something as corrosive as soda or salt it won't be able to protect it enough. The atmosphere is just too corrosive.

[Mark C.]

So I would say yes I have experience but in salt not soda which is less corrosive.

When you spary fiber and I have done it a lot you want to use a thin coating other wise the weight of it will  make it tear off (spall later)

zirconium is a fine coating. I use a spray gun made for spraying thicker materials

I have used lots of ITC  over the decades until it price went to the moon and now use my own private formula 

here is a post of mine from a few years back.

 

[Twitchy]

Thanks Mark. I suspect that a product called "Fibrecoat" might be better than the coatings tried in those links. it remains that I would like to find other trials before I do any trials myself. But it does not look very promising at this stage.

[neilestrick]

Fibrecoat sounds very similar to other zircon based coatings. The problem is that fiber shrinks, cracks, etc, and those small cracks will allow for penetration by the soda fumes. You just can't create a complete barrier with the coating. it may last a while if you're religious about re-coating it, but there's a reason everyone uses hard bricks for salt/soda kilns. It's been proven to be the best option.

[Twitchy]

I don'r doubt that, but it would be great if one could find a way to use fibre. The Furnascote non vit should crack less than some coatings. I have used it on fibre (not for soda) and it remains well intact. Another product, Fibrecoat, is apparently similar but designed specifically for coating fibre. I am trying to get further data on Fibrecoat.

[Twitchy]

I decided to explore the opinion of AI on matters related to this subject, so I asked Google Gemini AI a series of questions. The result is the  attached  "discussion" I had with Gemini. I have copied the "discussion" without reformatting or editing the text. I make no comment about the validity of this material. I simply offer it for your information. Please check it against other sources where appropriate. Note the Gemini disclaimer at the end.

  

Conversation with Gemini.pdf

[neilestrick]

14 hours ago, Twitchy said:

I decided to explore the opinion of AI on matters related to this subject, so I asked Google Gemini AI a series of questions.

Interesting stuff. The main thing it's missing is that the sodium is not just reacting with the silica. It also needs alumina in order for it to form the glaze. Pure silica will not be affected by sodium vapor. We used to dust flint onto our salt kiln shelves to protect them.

High zirconia blanket is about 15-17% zircon. It's in there primarily to bump up the heat rating of the  blanket. It may help protect from the soda, but not much. High zirconia bricks are 60+% zircon, so it's going to be considerably more durable than the fiber.

The life span of salt and soda kilns depends more on the amount of salt and soda being used in each firing than which one you're using. Salt kilns can outlast soda kilns and vice versa. In general, I see soda people using a lot more material than salt people.

Neither salt nor soda is more dangerous than the other, and your car will create many times more pollution than a salt/soda kiln being fired every week. Much of what comes out the stack is water vapor, and about 96% of the salt/soda that goes into the kiln comes out the stack as the same thing.

Read 'The Truth About Salt' by Gil Stengel in the Sept. 1998 Ceramics Monthly. HERE is some other good info. HERE is a good discussion.

[Mark C.]

You can always add some alumina to it.Just remember to keep it this on the fiber so it does not spall off from its own weight

[Ben Eberle]

Soda firing for over 20yrs now....and I have to agree with Neil on this one:

Like many of the "bendable" kiln rules out there....just because you CAN soda fire in a fiber kiln.....doesn't mean you SHOULD.

Anyone who has used kiln coatings in a combusting kiln will chime in and say that the upkeep is brutal...and, even with your best efforts, you will get flaking.

You're better off going with an IFB and a VERY thin high alumina wash. Bruce Denhert did that on Peter Valley's IFB soda kiln with over 50 firings on it...and it looks new. You simply have hit the chamber with a stiff bristled brush after each firing to gently remove and loose coating. If it looks good. Don't touch it. If it looks like it's compromised, apply a VERY light and thin coat - skim milk consistency. 

But Neil is right: There is a reason you have never seen a fiber soda kiln....and only VERY few soft brick soda kilns...