Chapter 7. Use of Fining Agents

  1. William J. Smothers
  1. H. N. Mills

Published Online: 26 MAR 2008

DOI: 10.1002/9780470320327.ch7

Proceedings of the 46th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 7, Issue 3/4

Proceedings of the 46th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 7, Issue 3/4

How to Cite

Mills, H. N. (2008) Use of Fining Agents, in Proceedings of the 46th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 7, Issue 3/4 (ed W. J. Smothers), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470320327.ch7

Author Information

  1. Owens-Illinois, Inc. One Seagate, Toledo, OH 43666

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1986

ISBN Information

Print ISBN: 9780470374658

Online ISBN: 9780470320327

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Keywords:

  • fining agents;
  • chemical compounds;
  • glass;
  • gaseous inclusions;
  • glass batches

Summary

The fining of glass involves the removal of gaseous inclusions. Two basic mechanisms are involved in this process: (1) buoyant rise of bubbles, and (2) dissolution of bubbles. Glass viscosity, temperature, time, and chemical kinetics influence the rate of fining. Fining agents are chemical compounds that can be added to glass batches to promote the basic fining mechanisms. Sulfate compounds are the most significant fining additives in oxidized soda-lime-silica glasses. The addition of reducing agents that promote decomposition of sulfate can further enhance glass fining. The application of redox factors to the oxidizing/reducing materials used in glass batch are very helpful in establishing equivalent fining benefit for different fining materials. Chemical analysis for retained sulfur and ferrous to total iron ratio determine the true redox of the final glass. Fining agents are selected on the basis of effectiveness, chemical consistency, handling characteristics and cost. With knowledge of the raw materials, glass composition, furnace and melting data, the glass technologist can provide a fining agent system to meet requirements.