Share from Insight-live.com (Lab Documentation and Calculation System) by Digitalfire. https://digitalfire.com
The chemistry of Minspar, a sodium feldspar, is very different than Nepheline Syenite, so substituting the latter in glaze recipes would likely be an issue. Let's make our synthetic Minspar.
Project Name Calculating a Substitute for Minspar 200 Project Codenumber UnAssigned Notes What happens when you cannot get a specific feldspar for use in a glaze recipe? In some cases, there is a similar feldspar that can simply be substituted, this is the case when the chemistries of the two materials are very similar. When a recipe only calls for 5 or 10%, then substitution is likely not a problem, even when the new feldspar is a little different that the old. However, when the recipe calls for a significant percentage (e.g. 30%+), which is normal since feldspars are the backbone of many glazes, then the situation becomes much trickier. That is the case with the recipe we studied, "Perfect Clear", it calls for 40%. That being said, feldspars are a little like Mother Nature's Frits, each one is different. Feldspars are almost a glaze in themselves, just needing silica and alumina to shift their chemistry toward that of a typical glaze. But that is where the biggest differences are: The percentage of silica and alumina. Here is the comparison of Minspar, Custer Feldspar and Nepheline Syenite, the three we have in stock:
Custer has a lot less Na2O and Nepheline has a lot more. Nepheline has significantly more Al2O3 less SiO2 than the other two. So, it seems that ny employing a blend of Custer and Nepheline diluted by the right blend of other materials it would be possible to produce a mix having the same chemistry as Minspar. So that's what I did. As you can see from all the tests, the substitute I calculated in my account at insight-live.com is "bang on" the very first try! Who gets the credit? The magic of glaze chemistry once again! |
Minspar
Total:100.00 Auto Unity Formula
Notes *I targeted this Minspar chemistry in calculating the substitute. Pictures Minspar vs. L4441B synthetic substitute Orton Autofire test kiln. Ball wts. 9.24 grams. XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Minspar" id="198278" key="Brufyj1p" date="2021-05-30" codenum="L4441A"> <recipelines> <recipeline material="Minspar 200" amount="100.000" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2021-05-19, Modified: 2021-05-30 16:05:46 |
Minspar Calculated Substitute
Total:100.00
Notes *These materials were used to supply the oxides needed to produce the same chemistry as Minspar 200. The trickiest part of the calculation was realizing that I needed a highly concentrated source of Na2O that was also low in Al2O3 - that is the reason for the small amount of frit. Pictures Minspar vs. L4441B synthetic substitute Orton Autofire test kiln. Ball wts. 9.24 grams. XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Minspar Calculated Substitute" id="198156" key="5Kv47iKy" date="2021-06-01" codenum="L4441B"> <recipelines> <recipeline material="Nepheline Syenite A270" amount="49.000" tolerance=""/> <recipeline material="Whiting" amount="1.600" tolerance=""/> <recipeline material="EPK" amount="9.000" tolerance=""/> <recipeline material="Silica" amount="19.800" tolerance=""/> <recipeline material="Ferro Frit 3110" amount="4.800" tolerance=""/> <recipeline material="Custer Feldspar" amount="15.800" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2021-05-17, Modified: 2021-06-01 17:48:50 |
Perfect Clear A well known cone 6 transparent
Total:100.00 Auto Unity Formula
Notes *This is a popular transparent cone 6 glaze. We use it for comparing feldspars in-glaze. Pictures G3925 Perfect Clear on M390, M340 Left: Uses L4441B Minspar subsitute G3925, G3925A glaze comparison G3925, G3925A glaze flow comparison Fired to cone 6. The calculated substitute for Minspar is used in G3925A, 40% of the recipe. The flows are identical. Untitled XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Perfect Clear" keywords="A well known cone 6 transparent" id="48913" key="Xn3Fxm9X" date="2022-03-02" codenum="G3925"> <recipelines> <recipeline material="Minspar 200" amount="40.000" tolerance=""/> <recipeline material="Gerstley Borate" amount="30.000" tolerance=""/> <recipeline material="OM #4 Ball Clay" amount="20.000" tolerance=""/> <recipeline material="Flint Silica" lookup="Silica" amount="10.000" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2013-12-13, Modified: 2022-03-02 14:45:35 |