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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 |
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.
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. |
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Materials |
Boraq 3
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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 |
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