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plaster molds for use in tile presses - question for experts and users

updated fri 10 nov 06

 

Paulette Carr on thu 9 nov 06


Recently I have heard from two people who use tile presses (2- ton
types), that they prepare the molds by combining #1 pottery plaster
and hydrocal or hydrostone. In one case the prep was done using
50:50 mixture by volume and employing the island technique. In the
other case, a percentage of pottery plaster to hydrostone was weighed
out, dry mixed with a ribbon mixer (?), and then prepared via the
weight or quantitative approach.

According to each of these people, the molds were harder (able to
withstand the pressure from the tile presses without breaking, but
still absorbent, and could still be carved right away, before they
cured.

Does anyone prepare molds of a mixture of pottery plaster and
hydrostone/hydrocal/ceramical. Can the plaster and gypsum cement be
mixed well in a low tech way without the aid of a ribbon cutter, and
still produce good molds without "swirling", or incomplete mixing of
the dry ingredients? Can this be done with the weight to weight
method (quantitative), rather than the island technique?

The advantage to making a mold that is slightly (to more) durable
than straight plaster, carve-able, and that will release without
purging is very intriguing!

Thanks, in advance for any information!

My best,
Paulette Carr

Paulette Carr Studio
Member/Potters Council
St. Louis, MO