Tom Buck on thu 27 may 99
Greetings all:
A request for up-to-date analyses of Nepheline Syenite and
Gerstley Borate prompted me to supply the following, with a great big
assist from friend Ron Roy who is able to elicit co-operation from Hamill
& Gillespie, the company in eastern N.America that supplies GB.
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J-M:
Here are the analyses you wanted:
Nepheline Syenite Canada (weight percent)
60.7 SiO2; 23.3 Al2O3; 0.07 Fe2O3; 4.6 K2O; 9.8 Na2O;
0.7 CaO; 0.1 MgO; 0.7 LOI.
Nepheline syneite, South African (courtesy Toni Martens)
61.5 SiO2; 23.8 Al2O3; 9.9 Na2O; 4.8 K2O which ignores the tiny
amounts of CaO, MgO, Fe2O3 and moisture H2O free and bound.
Gerstley borate is complex... the grade has been shifting steadily
with these numbers being the "average" of several tests, and all I can do
is give you the 1993, 1997, and 1999 levels in weight percent, the latter
two as reported to Ron by H&G:
Gerstley Borate, as cited by Hamill & Gillespie to Ron and me:
as of 1993: 9.8 SiO2; 1.3 Al2O3; 0.35 Fe2O3; 0.14 K2O;
4.7 Na2O; 17.9 CaO; 3.5 MgO; 23.3 B2O3; 34.0 LOI.
as of Aug 97: 11.73 SiO2; 1.63 Al2O3; 0.48 Fe2O3; 1.38 K2O;
4.39 Na2O; 19.06 CaO; 4.10 MgO; 27.68 B2O3; 29.35 LOI,
as of May 1999: 21.2 SiO2; 7.0 Al2O3; 2.9 Na2O; 18.9 CaO;
25.7 B2O3; 22.5 LOI.
As you will see, if you have a successful recipe containing GB, and now
it is causing problems, you will have to know when the glaze recipe first
was designed to know how to adjust for today's GB which is
much more refractory (more SiO2 and Al2O3) than before.
Good tests. BFN. Tom.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
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