Chapter 10. The Unity Molecular Formula Approach to Glaze Development
- William M. Carty
Published Online: 26 MAR 2008
Copyright © 2000 The American Ceramic Society
Materials & Equipment/Whitewares: Ceramic Engineering and Science Proceedings, Volume 21, Issue 2
How to Cite
Carty, W. M., Katz, M. and Gill, J. (2000) The Unity Molecular Formula Approach to Glaze Development, in Materials & Equipment/Whitewares: Ceramic Engineering and Science Proceedings, Volume 21, Issue 2 (ed W. M. Carty), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294611.ch10
- Published Online: 26 MAR 2008
- Published Print: 1 JAN 2000
Print ISBN: 9780470375679
Online ISBN: 9780470294611
- glaze development;
- unity molecular formula(UMF);
- molar calculations;
- glaze nature;
- hazardous materials
The unity molecular formula (UMF) approach to glaze development is commonly included in almost all undergraduate ceramic art curricula. Artists frequently complete the class and return to the studio excited with the possibilities of applying “science” to solve glaze issues. What they frequently discover is that the UMF approach does not work and they return to the trial and error methods and other information obtained from other artists. (Frequently you will hear of glazes with colorful names such as Pete's Red, Jane's Turquoise Blue, etc.)
Our work, conducted with the Glaze Calc summer school class at Alfred University, demonstrated that the UMF limit formulas were at the same time over-simplified and too complicated. The trend within the art community, as well as with industry, has been to develop glazes that are environmentally friendly (by eliminating oxides of lead, barium, strontium, etc.) and produce the broadest color palette (thus eliminating oxides of zinc, magnesium, etc.) Over the past 30 years, art glazes have been moving to much simpler compositions, mainly SiO2, A;2O3, CaO, K2O, and Na2O. From this perspective, the UMF limits are too complicated and are not well suited for use with the simpler glaze formulations.
The UMF limits are overly simplified in the context of the development of matte surfaces. Two types of mattes are possible: silica-based and alumina-based. The UMF limits only predict one of these possibilities.
This paper addresses the UMF limits, proposes new limits, and specifically discusses the importance of CaO in the formation of glosses and mattes for cone 10 applications. Cone 5 and cone 04 glazes are also discussed.