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Matt Russell

Calcium Carbonate (Lime/Whiting) as a Kiln Wash for Wood Firings?

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I was wondering if anyone has played with the idea of using whiting (calcium carbonate) as a kiln wash.   My logic comes from the use of seashells (calcium carbonate) on glazed surfaces of pots.  After the firing, the shells dissolve when soaked in water, just leaving a scar on the glaze.   Logically, I would think if a big glaze drip falls on the shelf coated with lime (also calcium carbonate), after the firing you could just spray water on the area, let the wash dissolve, and easily free the glaze drip.  I cant find anything online of anyone even  considering this.  If agricultural lime could be used it would be ideal, as I can get it for 2.50 per 50# sack,  which is much cheaper than both EPK and especially alumina hydrate.   I fire a large wood kiln to cone 10 and beyond, so the atmosphere can be volatile, and the standard kiln wash isn't working as well as I want.

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More alumina is your best friend on this. It has the highest melt temp..50% alumina 25% calcined EPK and 25% regular EPK works great in my salt kiln and in any wood kiln.

The only way is to test your idea-I think its going to not work well but let us know how it works-I would only use it on 1 shelve got see.

 

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I looked up some properties of quicklime, what is produced when lime is heated past 1500 degrees.   It sounds like some rough stuff, so much so that clouds of quicklime dust were used as a chemical weapon in ancient times.   I will do some testing, hopefully I can make something that works while also sticking to itself enough that it doesn't create a caustic cloud of dust. Ill post  results as I get them.

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Money is the main factor,  but also just the thought of trying something different.   I know that pure alumina is a relatively new material in comparison to the ancient history of pottery.  I was expanding on the process of using seashells as a wadding material.

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Hey Matt that's an awful lot of seashells if you have a large kiln. I've never used them but I have used lots of wadding making nearly 1200 on each glaze firing. I make mine out of epic and alumina with sawdust thrown in to make the wads porous and easier to remove after firing.  Never tried the lime as a kiln wask but I'm sure interested. Please keep us posted!!!+

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Never heard of using a flux as a kiln wash before.

I used to use a mix of 50% alum hydrate, 25% EPK, 25% Calcined EPK like Mark said above. I added in 1-3% of G200 (start at 1% and add it in more inrements until the fired kiln wash is no longer soft enough to dent with your finger nail, but soft enough to scratch with a nail/screw). The calcined EPK keeps the shrinkage down, and the G200 helps harden/bond the wash to the shelf and itself. I would build up 1/2" thick layers of this on my shelves over numerous firings.

If you've got a large wood kiln, spent all that money on this HD's, spent all the time splitting wood, then what does it matter if you spent $20 on a bucket of kiln wash? Id be more worried about trying a sketchy substitute material out in your kiln only to find all your work wrecked, and your kiln/furniture permanently damaged, or like you said, creating chemical warfare in your yard.  Spend the money on a tried and true kiln wash and KISS (Keep.It.Simple.Stupid!).

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