Brad Sondahl on sat 27 apr 02
In Aug 2001 Ron Roy listed his kiln wash recipe (particularly for
porcelain)--80 parts Alum. Hydrate and 20 parts Ball Clay.
I started using it and was pleased with how I've been able to cut back
on applying it, particularly with my spitting crystalline glazes.
Then one day I mistakenly brushed on a test glaze which was in an ice
cream bucket identical to my kiln wash bucket. It was brushed on rather
thinly, and there wasn't a thick coating of wash on the shelf (which
would have aided chipping it off). So I boldly added a coat of kiln
wash and fired with it. None of the pots stuck to it. With subsequent
firings the glaze reemerged, but one more coat of kiln wash has restored
it to utility.
This recipe exhibits no tendency to crawl, although I haven't built up
thick enough layers of solely this wash to speak with authority on that.
On the theoretical side, it does make sense that if you want to avoid
creating a glaze on your shelves, you should avoid using a glassformer
(silica). Yes, the melting point of pure silica is ridiculously high,
but it likes to make glass with whatever odds and ends befall it.
Anyway, good recipe.
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