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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 suggestions.

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