  
REFINING BY USE OF
SULPHATE COMPOUNDS (PR 441)
Work on a non-polluting
refining
Antimony oxide and arsenic oxide are the most common refining agents
at art-glass production. Today the industry uses almost only the antimony
oxide which is less dangerous for the environment.
However, the authorities
make proportionately great environmental demands also upon the use of
the antimony oxide and the industry is enjoined to investigate other
alternative refining agents.
Previous results
The result of the project "Refining by cerium oxide" shows
that it is possible to achieve an effective refining also by use of
the cerium oxide. Larger content of the cerium oxide than of antimony
or arsenic oxide is however required. The glass refined by use of cerium
also became a faint tint of yellow. Because of that cerium oxide can
not be recommended at production of colourless glasses.
Sulphate compounds
as refining agent?
Sulphate compounds are daily used at refining of many different types
of glass. The general opinion of refining is that a temperature higher
than 1450 °C is required to obtain a glass with no blisters. Normally
such high temperatures are not achieved in conventional furnaces used
for art and domestic glass.
At production of
special glasses we have found those sulphate-containing glasses can
become free from blisters at considerably lower temperatures.
Investigation
of possibilities
In the project we will investigate the possibilities of using sulphate
compounds to refine art and domestic glass. The test includes, e.g.
different raw materials, contents and other additives.
Test in full-scale
If the results of the tests in the laboratory scale look promising we
will continue with refining tests with the cerium oxide out in the industry.
CURRENT
PROJECTS
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