We all know that kiln wash and shelf primer does not melt at high temperatures which enables it to form a protective barrier between kiln shelves and glaze or glass. But, did you know the secret to smooth and bubble free kiln wash is to warm the shelves prior to its application?
Before applying the kiln wash, heat the shelves in the kiln to around 150F / 65C for an hour or two. If you are heating multiple shelves, make sure to separate them in the kiln with posts. Your kiln wash will now flow effortlessly without forming those small, and frustrating bubbles. Pre-heating shelves also speeds drying and lessens the chance of cracking the kiln wash.
The Bullseye Glass Shelf Primer Guide is a great resource for kiln wash applications.
When you mix your kiln wash, it should compare to a nonfat milk consistency. Paint your shelf by applying kiln wash in complete thin coats. First in one direction, then in the opposite direction, varying north/south, then east/west, etc. You’ll need about 6 coats to properly protect your shelf from glass adhesion. I can’t stress enough that thin coats are always preferred over thick ones. Applying the kiln wash that is too thick will result in the kiln wash peeling back from the shelf after just one firing. If it does, just scrape off all of the kiln wash and start over with thinner coats.
Don’t forget to let the kiln wash dry before firing the kiln. The kiln-washed shelves are still wet if they are cool to the touch. Apply kiln wash to the top of each shelf but not to both sides as the underside of a shelf can flake onto the items underneath. If the kiln wash is gauged, scratched, or chipped, that’s when it’s time to scrape the shelf clean and reapply.
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