IFB kiln for Soda

November 2, 2010

The following is a summary of a series of email messages which I recently exchanged with Nils Lou regarding his current recommendations for constructing a soda kiln using insulated brick coated with ITC100HT.

Coated IFB Soda Kiln

In *The Art of Firing* (1998), I read your preliminary report of using refractory coatings to protect IFB from the erosive effects of sodium atmosphere and to increase emissivity. I would be grateful if you would answer a few questions....

More than a decade has passed since the publication of The Art of Firing. Would you now recommend building a new soda kiln of coated IFB ... or should I stick with hard brick?

Sure, I am still using the original kiln, but made the mistake of salting a couple times with "burritos". After repair I only introduce salt by spraying the salt/soda solution. All IFB were totally dipped.

Is that kiln made of K23's coated with ITC100HT?

Yes.

Do you fire to cone 9-10.

Yes.

Are you saying that as you constructed the kiln, you totally immersed each brick in ITC100HT - ie coating all six sides, not just the hot face?

Yes.

Do you dip the bricks into a bucket of ITC ... or paint it on?

Dip.

Do you have a specific gravity or some other measure of how thick the ITC100HT should be to coat the bricks?

No, thin with water to thin paint consistency.

How much of the ITC would I need to coat the bricks for a 40 cubic foot kiln?

5 gallons

Would I need to buy 5 gallons of the concentrated ITC100HT? ... or do you mean that I would need 5 gallons of the diluted mixture used for dipping bricks?

5gals. of ITC, diluted to 10 gallons or so.

Do you use the ITC as a sort of mortar, laying the bricks up with the ITC still wet? ... or do you let the ITC dry on the bricks before you lay them up?

No, let dry. 

Is there a benefit to coating the side of the bricks that faces away from the heat?

Yes. If you dip the brick completely you don't have to fool with orientation. Otherwise, no heating benefit.

Composition of ITC100HT

Is "ITC100HT" anything more than a good kiln wash that I could make myself using commonly available raw materials?

It is much more, and is a proprietary formula.

Are you saying that some of the material contained in ITC100HT is specially manufactured - not something I could buy by the bag from a ceramic materials supplier?

Yes.

Topcoat to increase emissivity


Would a topcoat of HUC be as effective in increasing emissivity as ITC296A?

HUC is no longer available to my knowledge.

It appears that I don't have many options to select from.

Apparently so.

In *The Art of Firing*, you said HUC was a slurry of silicon carbide and various suspending agents. How about a kiln wash composed of kaolin and silicon carbide powder?

You could experiment with SiCo3, sodium silicate, and clay--might be interesting.

I don't know how I would measure the benefit of an emissivity coating other than showing a reduction in gas used in firings. Once a kiln is coated, you would have to build a new kiln to test another coating formulation. Is there an inexpensive way to accurately measure the amount of gas used in a firing?

I got a used meter from the gas company, so I could measure the gas. Otherwise, if the firing time is reduced you could assume you were using less.

Sad Note added Jan. 2014: I just learned that Nils Lou died 12-25-2013, a few days before his 82nd birthday.