Potters & Sculptors - Making Rock from Mud
It seems my local supplier only sells Spectralux Opacifier which runs about 60% more than straight Zircopax. It is the same percentage of zirconium as zircopax. While it seems to have a smaller particle size I can't find anything else that suggests it is better. Anyone used it and have an opinion?
I am trying the Mastering Cone 6 recipe for Cone 6 Majolica. Would appreciate any feedback others might have on this glaze.
In addition, Ron Roy has been kind enough to supply me with some reformulations of his recipes in his book to account for the decreased potash content of Custer Feldspar and the fact that G-200 is unavailable in my area. I'm testing these now. The Custer reformulations worked well but the Minspar versions underfired during the test and did not produce the proper colors so I have to rerun those tests.
"Zircopax, ZrSiO4 is a brand name for various grades of zirconium silicate opacifier. The grade that Continental Clay offers is Zircopax-Plus and it is comprised of 94.0% ZrSiO4 on average.
Zircopax Plus is white in appearance and white to grey-white as an opacifier after firing.
As a sole opacifier zircopax is added to glaze and glass formulations in amounts that range from 3% to 12%.
If background opacity is the objective and other colorants are to be included, the use of Superpax rather than Zircopax is often recommended as an overall cost saving measure."
I have not found "Zircopax" for years. It's always been Zircopax-plus, Superpax, or something else. Tony at digitalfire.com notes that Zirconium prices have been moving sharply upward, which may be part of the high price you have found. See http://digitalfire.com/4sight/material/zircopax_1724.html for more info and the particle size issue.
Thanks George. I finally found an analysis of Spectralux. My local ceramic supply (Trinity Ceramics) supplies the potter trade and the commercial trade for hundreds of miles around. So I think what they carry is heavily influenced by their commercial customers. They can't explain why they carry it versus Zircopax Plus, Superpax or other versions.
I noticed the proportions of ZrO2 and SiO2 and particle size (1.4 microns) are pretty similar to what insight live shows for Zircopax. (just 50% more expensive). Anyway I am using it 1:1 for Zircopax in my formulas
|Properties of Continental Mineral Processing Spectralux Opacifier (ZrSiO4)|
|Typical Chemical Analysis (in weight %)|
|*ZrO2||Zirconium Oxide||65% Min.|
|SiO2||Silicone Dioxide||32.5% Typ.|
|AI2O3||Aluminum Oxide||2.0% Max.|
|Fe2O3||Iron Oxide||0.15% Max.|
|U & Th||Uranium & Thorium||475 Max.|
|P2O5||Phosphrus Pentoxide||0.09% Typ.|
|*Includes 1-4% Hafnium Oxide HfO2|