Gerstley Borate low temperature glazes

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See Also:
Common Gerstley Borate matte glazes
Common Gerstley Borate Glossy Glazes


Project Name

Gerstley Borate low temperature glazes

Project Codenumber

UnAssigned

Notes

Since Gerstley Borate has a high LOI and it seems logical that it would tend to create bubbles and imperfections in low fire glazes. However, in practice it is amazing how transparent and crystal clear some of the glazes based on it can be. This is a testament to how well it melts, even at firing temperatures below cone 06.

It is common to see Gerstley Borate in low fire glazes that also contain significant amounts of boron frit.

GB Honey Amber 04

Code #

G2826F

Materials Amt
Ferro Frit 3124 30.000
Gerstley Borate 26.000
Nepheline Syenite 20.000
EPK 10.000
Silica 10.000
Lithium Carbonate 4.000
Additions
Iron Oxide Red 8.000

Total:108.00

Auto Unity Formula

CaO 0.50
Li2O 0.16
MgO 0.07
K2O 0.04
Na2O 0.23
(KNaO) 0.27
B2O3 0.47
Al2O3 0.34
SiO2 2.30
Fe2O3 0.14

Ratios

Si:Al: 6.8:1
SiB:Al: 8.2:1
R2O:RO: 0.4:0.6

Expansion

7.9 (Molar:7.6)

LOI

12.1

Cost

0.10 per kg

Notes

Pictures

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="GB Honey Amber 04" id="67242" key="gKEsfoZM" date="2023-07-03" codenum="G2826F" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3124" amount="30.000" tolerance=""/> <recipeline material="Gerstley Borate" amount="26.000" tolerance=""/> <recipeline material="Nepheline Syenite" amount="20.000" tolerance=""/> <recipeline material="EPK" amount="10.000" tolerance=""/> <recipeline material="Silica" amount="10.000" tolerance=""/> <recipeline material="Lithium Carbonate" amount="4.000" tolerance=""/> <recipeline material="Iron Oxide Red" amount="8.000" added="true"/> </recipelines> </recipe> </recipes>

Born: 2000-04-18, Modified: 2023-07-03 21:40:16

GB:Frit Raku Glaze

Code #

G2826B

Materials Amt
Gerstley Borate 25.000 20.00%
Ferro Frit 3195 13.000 10.40%
Wollastonite 4.200 3.36%
Silica 1.200 0.96%
Ferro Frit 3124 64.000 51.20%
EPK 17.600 14.08%

Total:125.00

Auto Unity Formula

CaO 0.72
MgO 0.05
K2O 0.01
Na2O 0.22
(KNaO) 0.23
B2O3 0.61
Al2O3 0.33
SiO2 2.16

Ratios

Si:Al: 6.5:1
SiB:Al: 8.3:1
R2O:RO: 0.2:0.8

Expansion

7.5 (Molar:7.6)

LOI

8.0

Cost

0.14 per kg

Notes

*For brushing: CMC and Veegum .5 each
Add mason stains to the base

Pictures

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="GB:Frit Raku Glaze" id="67238" key="cPB3TuSo" date="2023-07-03" codenum="G2826B" picturebasename=""> <recipelines> <recipeline material="Gerstley Borate" amount="25.000" tolerance=""/> <recipeline material="Ferro Frit 3195" amount="13.000" tolerance=""/> <recipeline material="Wollastonite" amount="4.200" tolerance=""/> <recipeline material="Silica" amount="1.200" tolerance=""/> <recipeline material="Ferro Frit 3124" amount="64.000" tolerance=""/> <recipeline material="EPK" amount="17.600" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2000-04-18, Modified: 2023-07-03 21:51:31

Gerstley Borate Raku Base NS/GB

Code #

G2826N

Materials Amt
Nepheline Syenite 50.000
Gerstley Borate 50.000

Total:100.00

Auto Unity Formula

CaO 0.50
MgO 0.12
K2O 0.07
Na2O 0.31
(KNaO) 0.38
B2O3 0.53
Al2O3 0.33
SiO2 1.74

Ratios

Si:Al: 5.3:1
SiB:Al: 6.9:1
R2O:RO: 0.4:0.6

Expansion

8.9 (Molar:8.8)

LOI

15.1

Notes

*While there are many variations on this base, the 50:50 GB:Nepheline mix is typical. We have seen versions all the way to 80% GB and 20% Nepheline. This range of blends melts very well at cone 06 and most are remarkably stable and bubble free. The higher the nepheline syenite the greater the crazing (a desired effect in many raku applications).

For mixes toward the 80:20 end we suggest adding some silica, perhaps 5-10%.

Pictures

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Gerstley Borate Raku Base NS/GB" id="67459" key="DNwa6KR5" date="2023-07-03" codenum="G2826N" picturebasename=""> <recipelines> <recipeline material="Nepheline Syenite" amount="50.000" tolerance=""/> <recipeline material="Gerstley Borate" amount="50.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2000-10-26, Modified: 2023-07-03 22:44:44