CoE
CoE
is an abbreviation for coefficient of linear expansion. This has a very
specific definition which is not widely understood.
The
"linear expansion coefficient" is determined by a
laboratory test which expresses the average expansion rate from
room temperature to 300ÂșC. It ignores the more important range of
expansion for determining compatibility for fusing and the expansion
through the annealing and softening ranges as this graph shows.
It
also ignores viscosity, an important element in determining whether
glasses will "fit" each other on fusing. Not all "90"
expansion glasses are compatible.
The
two major factors in a fusing compatible glass are expansion
characteristics and viscosity. These need to be in balance with each
other within one piece of glass and with other pieces of glass with
which they are combined. There are other factors of course, because
glass chemistry is very complicated.
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