I.Lewis on tue 16 nov 99
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Encapsulated Cadmium Stains. And a note for Salt Glazers
I had not heard about these products before this strand started so I am =
curious
to know what they are supposed to be and do. Certainly, I know that some =
cadmium
compounds are extremely poisonous. Cadmium plating must never be used on =
food
utensils. Learned about this from my time in the metallurgical trades. But =
many
people seem to be talking in their postings about Cadmium as a metal. Is =
this
what is in the stains so that the colour develops through a chemical =
reaction
which takes place when the stuff is fired? From the name of the substance I
would have thought that the colour was contained in an inert casing which =
did
not react with glaze.
Can someone please clarify this. What do the manufacturers say?
I use cadmium based paints as watercolour. They are made form Cadmium =
sulphide
and Cadmium seleno-sulphide. In the hand book ( Kurt Wehlter) it states =
clearly
under Toxicity that they are not poisonous as paint pigments. Is this
information now out of date?
Ah, yes. Apparently Cadmium sulphide can react with Sodium chloride at high
temperatures to give Cadmium chloride which boils at about 960C (1760F). So =
I
will avoid putting any cadmium compounds on my pots when I next fire the =
Salt
Kiln.
Ivor, who enjoys using stains for underglaze decoration.
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