Saturday, 15 September 2012



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.