Boraq 2

Description: Plainsman Plastic Gerstley Borate Substitute

Oxide	Analysis	Formula
CaO	25.40%	0.76
K2O	0.50%	0.01
MgO	3.60%	0.15
Na2O	3.20%	0.09
B2O3	26.50%	0.64
Al2O3	2.40%	0.04
SiO2	11.90%	0.33
Fe2O3	0.10%	-
LOI	26.40%	n/a
Oxide Weight		122.87
Formula Weight		166.94

Notes

Boraq 2 is a Gerstley Borate substitute that was made by Plainsman Clays (developed under code number L3127G). It was an adjustment to the original Boraq 1 in response to these issues:

-The boron levels in Boraq 1 were deliberately higher than Gerstley Borate so that it would melt as well at low temperatures (GB has tramp minerals that no material made from more pure minerals will have). That meant that Boraq 1 was melting too much at cone 6.

-The MgO in Boraq 1 was also lower than GB (it contains very fine MgO-rich clay particles that source the plasticity, the Hectalite addition in Boraq 1 was not sufficient to supply it all).

-Boraq 1 was not working well with iron reds at cone 6. It seemed evident that this was because of either the lack of CaO or the lack of limestone-like minerals that occur in Gerstley Borate.

Boraq 2 adds 8 dolomite and 8 calcium carbonate to Boraq 1. The dolomite supplies the needed MgO. Gerstley Borate is basically calcium-borate, so adding the calcium carbonate dilutes the boron.

The chemistry of Boraq 2, Boraq vs Gerstley Borate (mole%):
Boraq 2 Boraq 1 GB
CaO 34.7 29.1 30.4
MgO 8.0 5.4 7.6
KNaO 4.6 4.8 5.7
B₂O₃ 34.3 38.9 33.8
Al₂O₃ 1.6 1.8 0.9
SiO₂ 17.2 19.5 21.6

While no longer manufactured, the process by which it was developed is over interest to technicians.

Related Information

Links

Materials	Boraq This Gerstley Borate substitute was available during the early 2000s. Its recipe and development are well documented but two materials are no longer available.
Materials	Boraq 3
Typecodes	Flux Source Materials that source Na2O, K2O, Li2O, CaO, MgO and other fluxes but are not feldspars or frits. Remember that materials can be flux sources but also perform many other roles. For example, talc is a flux in high temperature glazes, but a matting agent in low temperatures ones. It can also be a flux, a filler and an expansion increaser in bodies.
URLs	https://insight-live.com/insight/share.php?z=eeukDwSTt4 The Development of a Gerstley Borate substitute - Boraq The development from a rationalization of the Gerstley Borate chemistry to various stages of matching the chemistry and compromising to get closer to the firing characteristics and raw physical properties.

By Tony Hansen
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