Anytime you fire a piece in a kiln, you are doing it on a kiln shelf. Properly preparing your kiln shelves is essential for not only a good glaze firing, but for the longevity of your kiln shelves- (which are no small investment!) Kiln Wash is a white firing clay-based (kaolin and flint usually) mixture painted only on one side of your kiln shelves to protect against glaze drips. Kiln wash is sold by any ceramic supplier. I happen to be using a Glass type kiln wash, called Primo-Primer. I switched to this a few years ago due to my frustration with regular kiln wash chipping off and occasionally falling onto a piece during glaze firing, causing noticeable glaze defects. The main difference, is that the Primo Primer, although a type of kiln wash, is considered a glass separator, which has a more finely ground particle size than regular kiln wash. I've not experienced the annoying fly-away chips in the glaze firings since I have switched. Kiln wash is designed to come up with the glaze drips when encouraged to come off the shelf- (as I show with a scraper or a grinder or chisel) I am preparing kiln shelves for firing in electric kilns. For atmospheric firings, please consult other resources.
When applying any kiln wash- remember, it should be in very THIN coats- not thick coats (Primo Primer is a 5:1 ratio- I misspoke in the video) - and should be applied to a damp shelf so it doesn't dry instantly and become too thick. Also, keep the kiln wash about 1/4"-1/2" away from the edge of the shelves, or you may find that the wash may flake off and fall into/on pieces below. Successive thin coats are always better than single thick coats. Many people swear by regular kiln wash- and that's great! I don't intend to cast judgement that it is not as good... I just was frustrated with having some glaze defects in my pieces so I switched! Primo Primer is really intended for glass molds. I always use a Hake brush- which is very big and soft-bristled- for the application of the wash. Regular kiln wash only requires 2-3 coats, but the Primo Primer really needs more.
Note that I use patties under my fired pieces. They are waste pieces of clay which I put the pieces on, which also help add another layer of protection to my shelving during firing. Having 180 kids in my classroom each day requires lots of glaze firing, and having patties under their glazed pieces has kept me sane and from significantly less kiln shelf cleaning than when I was a new teacher! Here is a link to my video on making the clay patties that my students put under their pieces: • Making Patties or Cook...
And, as a side note: I use thin stoneware patties at home in my personal firings too. I (dip) kiln wash the patties however at home, to make them last much longer!
Link to the product Primo Primer: www.delphiglass.com/fusing-sup...
Granted, it is more expensive, and requires more frequent application, but it causes me less stress in the long run.
Here is a link for the abrasive rubbing brick: www.homedepot.com/p/Marshallto...
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