Project Name
Gerstley Borate Cone 6 Matte Glazes
Project Codenumber
UnAssigned
Notes
Gerstley Borate was used to create very nice magnesia matte glazes (using dolomite and talc). This might seem strange considering that GB is so fluid and naturally tends to form runny glossy glazes. But moderate to large amounts of magnesia change that. It acts as a filler and stabilizer to counteract the runny melt (not as a flux). However, with more magnesia comes less resistance to leaching and cutlery marking).
An interesting side effect of this mechanism is that calculated thermal expansion values are misleading. Likely the normally low expansion influences of MgO depend on them being active in the glass chemistry, that is not happening here.
Since the high MgO is the matte mechanism these glazes are good candidates for sourcing the B2O3 from a frit instead of GB. Those containing significant feldspar offer the opportunity to source Al2O3 from kaolin instead (the KNaO from the feldspar can be also sourced from Frit 3110).
GB Lavendar Satin Glaze Cone 6
|
Code # G2826G |
| Materials | Amt |
|---|---|
| Gerstley Borate | 21.100 |
| Nepheline Syenite | 12.300 |
| Talc | 11.800 |
| Dolomite | 11.800 |
| Spodumene | 5.000 |
| Ball Clay | 8.300 |
| Silica | 29.600 |
| Additions | |
|---|---|
| *Cobalt Carboante | 0.500 |
Total:100.40
Auto Unity Formula
|
Si:Al: 14.5:1 5.8 (Molar:5.6) 13.5 |
Notes
*This glaze takes the magnesia matte concept close to the limit (it uses both dolomite and talc to supply a lot of MgO). This is thus very matte, likely having cutlery marking issues.
Pictures
Untitled
XML (to paste into Insight)
<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="GB Lavendar Satin Glaze Cone 6" id="67243" key="DGpsMw64" date="2023-07-03" codenum="G2826G" picturebasename=""> <recipelines> <recipeline material="Gerstley Borate" amount="21.100" tolerance=""/> <recipeline material="Nepheline Syenite" amount="12.300" tolerance=""/> <recipeline material="Talc" amount="11.800" tolerance=""/> <recipeline material="Dolomite" amount="11.800" tolerance=""/> <recipeline material="Spodumene" amount="5.000" tolerance=""/> <recipeline material="Ball Clay" amount="8.300" tolerance=""/> <recipeline material="Silica" amount="29.600" tolerance=""/> <recipeline material="Cobalt Carboante" amount="0.500" added="true"/> </recipelines> </recipe> </recipes>
Born: 2000-04-18, Modified: 2023-07-03 22:48:25
Gerstley Borate Cream Oatmeal Cone 6 recipe
|
Code # G2826V |
| Materials | Amt |
|---|---|
| Gerstley Borate | 15.500 |
| Nepheline Syenite | 39.000 |
| Dolomite | 18.000 |
| Zinc Oxide | 0.700 |
| EPK | 6.300 |
| Silica | 20.500 |
Total:100.00
Auto Unity Formula
|
Si:Al: 7.2:1 7.5 (Molar:7.3) 14.3 Cost 0.06 per kg |
Notes
*This is an example of a glaze that is matte because of moderately high MgO content coupled with low melting. Since it does not depend on the reactivity that Gerstley Borate gives this would likely respond very well to efforts to source the B2O3 from a frit instead.
Pictures
XML (to paste into Insight)
<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Gerstley Borate Cream Oatmeal Cone 6 recipe" id="67634" key="c28GSfp5" date="2023-07-03" codenum="G2826V" picturebasename=""> <recipelines> <recipeline material="Gerstley Borate" amount="15.500" tolerance=""/> <recipeline material="Nepheline Syenite" amount="39.000" tolerance=""/> <recipeline material="Dolomite" amount="18.000" tolerance=""/> <recipeline material="Zinc Oxide" amount="0.700" tolerance=""/> <recipeline material="EPK" amount="6.300" tolerance=""/> <recipeline material="Silica" amount="20.500" tolerance=""/> </recipelines> </recipe> </recipes>
Born: 2001-05-24, Modified: 2023-07-03 22:17:58
Gerstley Borate Antique Green Cone 5
|
Code # G2826M |
| Materials | Amt |
|---|---|
| Gerstley Borate | 32.000 |
| Custer Feldspar | 35.000 |
| Dolomite | 14.000 |
| EPK | 5.000 |
| Silica | 14.000 |
| Additions | |
|---|---|
| Rutile | 2.000 |
| Chrome Oxide | 0.500 |
Total:102.50
Auto Unity Formula
|
Si:Al: 9.4:1 7.6 (Molar:7.2) 17.0 Cost 0.05 per kg |
Notes
*This recipe is an example of one that has to be applied and fired just right (cone 5 with quick cool) to achieve an opaque matte surface.
Pictures
XML (to paste into Insight)
<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Gerstley Borate Antique Green Cone 5" id="67430" key="aMFjsX7c" date="2023-07-03" codenum="G2826M" picturebasename=""> <recipelines> <recipeline material="Gerstley Borate" amount="32.000" tolerance=""/> <recipeline material="Custer Feldspar" amount="35.000" tolerance=""/> <recipeline material="Dolomite" amount="14.000" tolerance=""/> <recipeline material="EPK" amount="5.000" tolerance=""/> <recipeline material="Silica" amount="14.000" tolerance=""/> <recipeline material="Rutile" amount="2.000" added="true"/> <recipeline material="Chrome Oxide" amount="0.500" added="true"/> </recipelines> </recipe> </recipes>
Born: 2000-10-05, Modified: 2023-07-03 22:20:47
