[Jewelry making - Article 00500] - Re: [Orchid] Substitute for vermiculite and alumina hydrate?

[nick]

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    If you allow silica to come into contact with your kiln elements it
    fuses and makes hot spots which not only burn out the elements but
    also causes the silica to react with the fire clay bricks causing
    their melting to a glass which will eat its way through the
    surrounding refactory. You get a similar effect from fingerprints on
    500w tungsten lamp tubes which are silica. The salt in the
    fingerprint creates a hot spot and the silica reacts and forms a
    glass which then melts. I have several pieces of kanthal and SiC
    with quartz crystals growing on them from contact with silica sand
    and many pieces of kaowool and the like with silica that has corroded
    its way through it. You only need to get it to melting point once and
    then the new compounds will melt at a lower temp and so it
    continues. In the UK the kiln shelves are known as batts or bats so
    perhaps it is used as a generic term for a flat surface. 

Nick
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