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fire clay, grog, propylene glycol & cone 5 b-mix

updated thu 15 oct 98


Jim Kassebaum on wed 14 oct 98

In response to Llewellyn K's 10/11 posting re: (1) calcined fire clay; (2)
brick clay grog; (3) Molochite and (4) the best bodies for large sculpture

There are books available which describe these materials in far greater
depth, but here are a couple of thoughts.

Calcined fire clay and grog are essentially the same but of varying mesh
sizes. Grog is usually either calcined fire clay or calcined kaolin. 20F
is a good grog size for sculpture bodies as is a 20x48 grog (e.g. Ione)
which is a tight range of mesh sizes which seem to work well to provide
strength for larger forms. Brick grog is typically made from ground junk
bricks or seconds. We do not recommend it for your use. It is typically a
lot of powder at one end of the spectrum and really coarse at the other.
Molochite is an expensive calcined kaolin grog which probably isn't
necessary for your work.

For large sculpture work we recommend a body with Lincoln 60 or Hawthorne
Bond (or similar fireclays) and a mixture of grog and sand. Although many
eastern clay bodies use grog exclusively, we find that a body with a mixture
of grog and sand is more forgiving when it comes to glazing. Either way
your local ceramic supplier should be able to help you out. And if you
really enjoy creating art rather than clay, there are a lot of good prepared
sculpture bodies on the market.

Re your majolica/propylene glycol question: Laguna has propylene glycol, but
I believe you will find glycerin a very satisfactory substitute. We offer
it by the pint and the gallon.

Re: Jenny Dubats & Cone 5 B-Mix -- As with most Laguna Cone 5 bodies (one
exception being Cone 5 Porcelain), Cone 5 B-Mix should fire well at Cone 6
or even Cone 7 or 8. Most of our bodies have a wide range, but we designate
them at the temperature (Cone) where our QC tests are performed. I'm
available for further discussion!

Joe Koons Laguna Clay Co.
(800) 4-LAGUNA (452-4862) X 227
(626) 330-0631 x 227, fax (626) 333-7694;