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glaze faults & tile problems

updated sat 31 aug 96


Alfred O. Smith on sat 31 aug 96

Keith Chervenak wrote:
>A tile making friend is experiencing problems with his glaze
>coming off the side (edges) of his tile...[snip]...This is
>happening with sporadic occurence with all his glazes.
>The inconsistency of how and when it it occurs is what is
>so puzzling to us. Any thoughts or ideas out there?
>All help is appreciated for this frustrating problem.
>Steve Hoskin wrote:
>I recently purchased my first kiln and am firing to cone 6
>(oxidation). I have been making my glazes from base
>chemicals for the first time and many of my pots have
>emerged from the kiln with bald areas (small but obvious
>unglazed spots). Does anyone know why this is? Any

Hello. My name is Al Smith and I'm one of those lazy lurkers. Haven't
worked with clay for the last twenty years or so and been too busy
raising brats (who are now having wonderful grandchildren). I am in the
process of designing a gas kiln which I hope to build before I get too
old to lift the bricks and have been lurking around Clayart for a couple
of months.
I don't have a great deal of experience with clay and glazes but have
suffered problems in other fields with contamination from silicone oils
and sprays. I have seen a number of posts on Clayart recommending a
squirt here and there for noisy belts and squeaky wheels. Has anyone
considered/experienced problems with contamination from these so-called
lubricants? (They don't lubricate very well). They are used almost
everywhere for mold releases, belt dressings (noisy throwing wheels) and
waterproofing sprays for earthenware flower pots, etc. Silicone
contamination has caused major problems for virtually every industry
trying to stick anything together or trying to wet or clean a surface.
The electronics industry has had severe problems with contamination of
soldering operations to the extent it has almost bankrupt some companies.
The stuff gets on everything you touch and it is amazing how little it
takes to screw things up. I have had numerous problems with painting,
both wood and metal, and bonding operations with rubber, metal, &
plastics at work. The spray cans sold for automotive use and use on
squeaky doors are the worst - one puff coats a whole room. In one plant,
where silicone contamination repeatedly shut down the production line of
a rubber bonded product, a persistent source was traced to contaminated
steering wheels on the company vehicles used in the plant.
I can't believe that silicone contamination could cause problems at
temperatures much above 10000F (what's a little more silica to a pot?)
but it certainly could cause problems if you used silicone lubricants on
equipment that came in contact with raw clay/greenware to be glazed (tile
cutting?) or if spray settled on bisque before the glaze was applied.

>From the Mojave, where today may be cooler than yesterday's 1110F (that's
440C to the real world)

*Al Smith*
*1033 Mary Ann Ave. *
*Ridgecrest, Ca 93555 619.375.4131*