KILN WASH FORMULAS
While it's easy to purchase a pre-made kiln
wash, some people prefer to make their own. It's not difficult to
mix up your own kiln wash formula; you can even custom make the type
of kiln wash that you prefer. There are a number of alternative
formulas (two are given below), but it's generally a good idea to
use a formula that has been created with glass in mind -- some
formulas are best used for ceramics only.
The basic formula for kiln wash is alumina
hydrate and kaolin (also known as china clay, mixed 50/50 by
volume. Obtain the two ingredients in powder (or flour) form, then
simply mix the two powders together, add water to your desired
thickness (about 4 or 5 parts water to one of powder), and apply to
the kiln shelf. Most people apply by spray or haike brush in
several coats. The shelf is ready to use when the kiln wash is dry
(if desired, you can speed up the drying by heating the shelf in a
500F/250C kiln). This formula can generally be used for several
firings, and should be scraped off and reapplied once it starts to
flake or wears thin. (Note that this formula will work well for
ceramics also, so it's a good multi-purpose kiln wash.)
An alternative kiln wash formula, which works
best for float glass but can also work for other glasses, is to mix 80% alumina hydrate and 20% kaolin. This produces a kiln wash powder that is
softer than the standard mixture. Only one coat is needed on the shelf, and you can apply by
brush or spray. It's a single use formula; after each firing,
remove with a damp paper towel (no scraping needed!) and then
reapply. It's important to remove the kiln wash after each firing;
if you leave it on, it can discolor the glass on future firings.
The two main chemicals in these kiln washes --
alumina hydrate and kaolin -- are commonly used in ceramics can be
found at most ceramics supply places. If you are unable to find the
chemicals in flour or fine powder form, you can use a mesh screen to
screen out large particles and made the recipes work well for glass.
A 120 mesh screen generally works well.
Copyright 2005 Brad Walker.
All rights reserved.
Thanks to Bert Weiss, Brian
Blanthorn, Michael Ray and others for passing on these formulas and