Kiln Wash Simplified

Brushing this mixture of alumina hydrate and water on your kiln shelves can cut down on hassle and studio expenses.

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 Harnetty, editor.


 

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.

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.

Comments
  • Sylvia,

    Great tip! much easier to use, and the clean up is a breeze..
    Thank you so much…

  • 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.

    Marge

  • 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 Add enough water so that your slurry is the consistency of cream or whole milk.

  • 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 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.

    Verna

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

  • 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!-

  • does anyone know the formula for making those small balls to place between glazed lids and pots during a firing so they do not stick together?
    please send to rgraebner00@comcast.net

  • 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.

  • 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?

  • 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.

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