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INSIGHT Software, the best way to deal with this: Watch the Gerstley Borate video here.

PV GB Base Glaze

The Plastic Vitrox Gerstley Borate combination has been very popular and used for many years as a base glossy glaze for cone 6 (so we have dedicated a separate page to it). This recipe doubtless originated in California since PV Clay is mined there and was in common use since the 1970s and perhaps earlier (i.e. the California Artware casting body contained PV Clay). Since this recipe is comprised entirely of clay-containing minerals it shrinks and cracks off ware if it is applied too thick. On the other hand it makes a good slip to apply to leather hard ware since it will shrink with the clay as it dries. To learn more about PV Clay click the link below.

To create a white from this most people add 10-20% zirconium silicate.

We do not anticipate a problem using Boraq with this recipe. If you are mixing your own Boraq you have the option of leaving out the Hectorite to reduce the drying shrinkage.

INSIGHT 5.3 Comparison Report

PV Clay:Gerstley Borate Base Cone 6 PV Clay:Boraq 2 Base Cone 6
  Amount %  
Gerstley Borate 50.00  
PV CLAY 50.00  
  Amount %  
PV CLAY 50.00  
Boraq 2 50.00  
Analysis Mole%
CaO 0.63 11.5 15.5
MgO 0.15 2.0 3.7
K2O 0.09 2.6 2.1
Na2O 0.13 2.7 3.3
Al2O3 0.21 6.9 5.1
B2O3 0.64 14.5 15.7
SiO2 2.21 43.3 54.4
Fe2O3 0.01 0.3 0.2
  LOI 16.2  
Analysis Mole%
CaO 0.65 11.6 15.3
MgO 0.16 2.0 3.7
K2O 0.09 2.8 2.2
Na2O 0.10 2.0 2.4
Al2O3 0.23 7.5 5.4
B2O3 0.70 15.4 16.5
SiO2 2.29 43.8 54.2
Fe2O3 0.01 0.3 0.2
  LOI 14.4  
Tony Hansen

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