Kiln Wash Simplified

Protect your kiln shelves with kiln wash!

kiln wash

Most potters don’t give much thought to kiln wash and just use the recipe they used when they first learned about firing kilns or grab whatever happens to be in the kiln wash bucket. Consideration of kiln wash might help potters avoid some of the common kiln wash headaches – like scraping cracked kiln wash off shelves or lamenting an otherwise perfect piece that was ruined by a flake of kiln wash. This week’s Tip of the Week comes to us from ceramic artist Sylvia Nagy of Brooklyn, New York. If you are tired of scraping and cleaning kiln shelves between firings, you’ll love this simple tip. — Jennifer Poellot Harnetty, editor.

Worried about your kiln wash flaking?

Kiln wash is usually a mixture of alumina hydrate and kaolin. If kiln shelves with this typical mixture of kiln wash are not scraped and cleaned in between firings and the kiln shelves are flipped between firings to prevent warping, pieces of kiln wash can flake off, drop onto glazed ware and ruin the surface. Kiln wash should be used in both electric kilns and gas kilns.

A Guide to Ceramic Kilns

Find helpful tips for choosing the right kiln firing method when you download this freebieA Guide to Ceramic Kilns.


I have found that using alumina hydrate mixed only with water eliminates the problem of flaking kiln wash and works just as well. I just brush the mixture on my kiln shelves and, after firing, it becomes powder again. Cleaning the shelves is as easy as brushing the powder from the shelf. You can even save the powder, remix it with water and use it again next firing. An added bonus is that the powder enables the ceramic pieces to move a bit during the firing, which cuts down on warping that my occur during shrinkage.

Do you have any kiln wash tips or recipes that you’ve found success with? Share them in the comments!

**First published in 2008.
  • Geoff K.

    Alumina hydrate as a bat wash in a gas kiln is likely to cause you problems. In a gas kiln, when the wash has dried, it is likely to be moved by the flames and thus onto your ceramics turning them into sand paper! If used in an electric kiln – no problems. As a wash under/on the foot of a pot in a gas kiln I can see it should work but care as always is essential.

  • Sue Y.

    For my current kilns (firing electric). I have older traditionally kiln washed shelves that I use in the base of the kiln with a thin layer of medium grog spread over the surface. They stay in there all the time and only come out for kiln maintenance. If I’m firing test tiles/pieces or pots that I think might run they go on bottom shelf. The rest of the shelves are not washed and only use layers of grog for larger pieces or brush the alumina hydrate and water thin paste on the foot of porcelain pieces or other clays of that nature. The alumina hydrate sponges off the feet after firing and the grog gets brushed off back into a flat tray box and reused. I always do a final dust off with an old T shirt rag so the shelves are flippable. When loading the kilns I do a sight line along the shelves straight edge and flip the shelf accordingly. Shelf sets are 10 and 12 years old and all nice and flat. Occasionally have had a glaze drip on the unwashed shelves and delicate use of an angle grinder eliminates the drip with minimal effect.

  • Janet C.

    What????!!!!! This is AMAZING information. I cannot wait to try this. Why have I never heard this before? Thank you!

  • Adrian C.

    Just took over an electric kiln (7cu ft)together with a bunch of stuff…glazes, clay, tools etc. I found a 5 kg bag of ‘Alumina Hydrate’. Been reading responses by members. Please advice…can I treat it as ‘kiln wash’? Would it be useful to coat mandrils for glass bead making? Thanks.

  • Roger S.

    One health concern is dealing with the dry alumina after firings. Use an appropriate respirator if brushing it off the fired kiln shelves. Probably not good to inhale it. Maybe wash it off instead?

  • Subscriber T.

    I use a 50/50 mixture of alumina and EPK with water until is balls up. Attach to the pot with white Elmers glue. Here is also an article from CAD. There are numerous recipes found on google under kiln wadding.

  • I’ve tried this and can’t say that I would recommend it. The feet of my pots stuck to the shelves and big chunks of clay were pulled off the pots. They’re ruined!-

  • Verna L.

    OK, after trying one this coat, I don’t know if I can get another one over it. What do you think?

  • Verna L.

    I have heard this before and was searching the internet to see if anyone else agreed. Being a self taught potter I did not know NOT to kiln wash BOTH sides of the shelves. Also I was not told the correct consistency, consequently ended up with way to thick and too many coats and it turned to concrete but will still flake off no matter how many times I scrape them.

    So my point is this is wonderful news and I am going to give it a go. I was told two thin coats drying in between and no thicker than a business card.

    Thanks Sylvia and I shall report on my results.


  • Arlene C.

    Hello, I have held onto this tip and have tried the alumina hydrate mixed with water. I’m not getting an even coating and the product seems to dry out (return to powder) almost as I’m applying it. The mixture is quite watery. Any suggestions?

  • I used 95%of Alumina and 5% of Kaolin mixed with water and apply on kiln car shelf. It is lasting for more firing.

  • Marge H.

    How much water do you add to what amount of prepared kiln wash?? I have not used this before, but am now beginning to fire at higher temperatures. Thank you for any help.


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