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copper sulphate (was copper phosphate)

updated fri 26 may 06


Bob Masta on thu 25 may 06

> >Any tips from other experimenters on this or other chemicals used in raku
> >and sagger firing would be appreciated...

Haven't tried this in raku, but soaking bisqued ware in copper sulphate
and firing it gives a nice matte-to-satin black to the body itself at cone 6
oxidation. Drips of clear glaze onto this have interesting green fringes.
You need a fair amount of copper sulfate for this to work... a quick wash
with a brushtroke or two may give poor results. Try dipping for several
minutes at least. I used a saturated solution made simply by throwing
some copper sulphate crystals into water and letting it stand for several
days; give it plenty of time, and make sure there are excess crystals
so that everything that can dissolve will do so. (If there are no crystals
left after several days, throw in some more and wait some more.) I
just store the solution with the excess crystals in the bottom. You
could of course speed up the dissolution by heating it, but who wants
to mess around with hot copper sulphate?

Needless to say, this is for decorative work only... not for food!

Best regards,

Bob Masta