Technical Tuesday: What Makes A Glaze Shiny?
- , by Haley Stanaford
- 2 min reading time
All glazes are made of three, integral components: glass formers, fluxes, and clay. These materials provide different amounts of molecules of compounds and elements (as seen on the periodic table) that work together to form your glaze. Glass formers are the key to making glazes shiny by creating structures of glass. Adding more of a glass former makes a glaze shinier. Fluxes impact the melt of the glaze, therefore, more flux equals more melt. The clay portion of a glaze suspends the material in the glaze mixture and allows the glaze to adhere to the ceramic surface.
This molecular makeup can be seen and analyzed through the Unity Molecular Formula, commonly referred to as UMF. There are many UMF calculators available to use online, a great, accessible, and free to use one is on Glazy, under the calculator tab. You can put in any glaze recipe by putting in the materials and amounts and see lots of information without having to do the scary math of UMF. I have put in Tony Hansen’s G2926B Cone 6 Transparent, which you can find images and more information about here.
Within the calculator, you are able to see a glaze’s Silica (SiO2) to Alumina (Al2O3) ratio. These compounds are present in all glazes and determine what makes your glaze shiny! The numbers that appear correspond to a glaze finish, which is shown in this chart:
|
SiO2:Al2O3 Ratio |
|
|
0-2.6 |
Not Melted |
|
2.6-4.3 |
Matte |
|
4.3-5 |
Semi Matte |
|
5+ |
Glossy |
These numbers for Hansen’s glaze in our glazy calculator appear as a graph in the top left corner. When hovering over the glaze’s graphed dot, you’ll see a breakdown of the numbers.
To find the finish of the glaze, we are looking at that red number. In this case, the SiO2:Al2O3 is 9.25! That’s a glossy glaze! So if you don’t know if a recipe will be shiny or matte, hop over to a UMF calculator and find the answer super easily!
Haley Stanaford is currently a Post Baccalaureate student in ceramics at the University of Kansas where she is currently taking a Clay and Glaze Formulation taught by Colby Charpentier in addition to her studio practice. She also is a Sales Representative at Bracker’s Good Earth Clays in Lawrence, Kansas.
