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kilns and reku and toxic glazes

updated mon 12 jun 00


Gwyn Ace on sun 11 jun 00

If you have a kiln with no instructions..if you have a pyrometer..then =
it should be easy to plan a temp rise Start very slow to remove any =
remaining moisture then chemically combined water will be released. This =
stage should continue until no moisture can be detected.. ..use a cold =
mirror near the vent..then climb slowly until a good red color is =
seen..then when all carbon etc. has burned off a faster climb is O.K. to =
temperature. If you are too slow then you are just wasting a bit of your =
time and a bit of extra power. For a medium size kiln..about 8 hrs to =
10 hrs for bisc is fairly normal and about the same time for a glaze =
firing which does not need such a slow start. You will not give yourself =
problems by firing a bit slowly but too fast can give explosions of the =
ware etc. I have never had any instructions for any kiln and just use =
careful and slow as the guide.
Robert Fournier's book on Electric Kiln Construction gives a good =
rundown on the changes taking place in the firing.

As most Raku Glazes are not food safe ..I cannot see where waterproofing =
pots is appropriate unless a vase or similar is involved...but I =
wouldn't suggest that such a pot should be used on an expensive Grand =
Piano !!! Better leave Raku for decorative pots where the potential =
toxicity of the glaze and waterproof is not fact an old =
friend Rosemary Perry recommends that Raku or similar bottles..jars etc =
which are not food safe should be labeled "decorative pot " Not =
waterproof" and she suggests a hole in the bottom of the that =
any later owner will not misuse them.
Gwyn in N.Z. where we try to play safe...