GERSTLEY BORATE: Replacing it in your glazes

to source boron from something other than
Cadycal since it does not have these, or
you'll need to use a combination of Cadycal
and feldspar'Nepheline Syenite.

Fire samples of your new recipe and make
adjustments if necessary to maintain the
visual character. Have the glaze tested for
leaching. Find information about this in
the January isste of see http:/!
digitalfire.com/education/ glaze!
leaching. hem, If the glaze fails the test, try
to rationalize the formula according to the
information from these two sources; ad-
just and test again.

A Challenge

I believe itis possible to formulate amix of
Cadyeal and the night clay and a little
feldspar to duplicate the physical and
chemical properties of GB. The material
that Ravenserag Slip is based on has a
makeup that complements Cadycal to pro-
duce a GB like chemistry. It would have
even betterflow properties. The mix would
be adjustable and much more consistent.
More word on this as it develops.

Cadycal
This material is being touted by some as a
successor to GB. Be careful; there are
some caveats. First, a litthe background:
Cadyeal is a calcium borate mineral pro-
duced by Fort Cady Minerals Corp of
Newberry Springs, CA. Their plant is in
the same area as US Borax and other boron
producers. The ore body from which
Cadycal is made is 1400 feet below the
surface. The mining is done by drilling
wells into the ore bxdy and injecting a
solution af diluted sulfuric acid. The re-
sulling boric acid is pumped to the surface
and reacted with lime to produce a pure
calcium borate that is dried and packaged.

The approximate chemical analysis from
the manufacturers brochure is:

CaO 25.0%
MaQ 0.3%
B203 48.0%
Si02 0.7%
LOL 25.0%
Mary Simmons at the Department of Earth
and Planetary Sciences at the University

of New Mexico analyzed @ sampic:

S102 (Le
AI203 O04
MnO O03
MgO 0.24
Cad $0.80
P2305 O02
LO] 24.44,
B203 43.81

She got the boron figure by subtracting
everything (majors + LOL from 100. Her
further comments were: “The gb samples
I analyzed for LOA all melted in the cruci-
ble to a clear/yellowish glass alter sitting
in the 1OQMKS furnace for one hour. The
Cadycal did NOT completely melt — there
was glass + whitish stuf! after an hour in
the 1O00c furnace,"

Cadycal has twice as much boron as
Gerstley and therefore it is very different
chemically. It is completely different
mineralogically as well. Remember, many
GB glazes depend.on it for suspension and
hardness and flow properties and Cadycal
will not impart these.

available through:

The only clays made from
Canadian clay deposits

A complete line of products is

PLAINSMAN intes

Box 1266, Medicine Hat, Alta. T1A 7M
Phone 403-527-8535 FAX 527-7508
Intemet: http:digitalfire.corm/plainsman

Greenbarn Potters Supply Surrey, 8.C. Phone: 604-888-3411
Vancouver Island Pottery Nanaimo, 8.C. Phone: 250-716-9966
Warehouse Inc.

Apni 2000

Potters Guild of Bntish Columbia