Friday, 19 February 2010

Temperature Characteristics of Various Glasses

Over the years I have collected temperature information for a number of glasses. They are of comparative interest and can assist with choosing a temperature or range of temperatures for the work you are doing. If the work is important, or critical, refer to the manufacturer for the latest information.

BullseyeThere has been a lot of information published about this glass. One interesting characteristic has been the different temperatures for the complete range of glass they produce. So there appears to be a difference between the transparent, opalescent and gold pink glasses.
Transparent:
Full Fusing 832C ; Tack Fusing 777C ; Softening 677C ; Annealing 532C ; Strain 493C
Opalescent:
Full Fusing 843C ; Tack Fusing 788C ; Softening 688C ; Annealing 502C ; Strain 463C
Gold Bearing:Full Fusing 788C ; Tack Fusing 732C ; Softening 635C ; Annealing 472C ; Strain 438C

This also illustrates that not all the characteristics of a glass range are linear. The most apparent one is that the full fusing, tack fusing and softening points of the opalescent glass are higher than transparent, although the annealing point is lower.

Desag GNA
Full Fusing 857C ; Tack Fusing 802C ; Softening 718C ; Annealing 516C ; Strain 427C

Float GlassFull Fusing 835C ; Tack Fusing ca. 760C ; Softening 720C ; Annealing ca. 530C ; Strain 454

Spectrum S96Full Fusing 788C ; Tack Fusing 718C ; Softening 677C ; Annealing 510C ; Strain 371C

UroborosFull Fusing 788C ; Tack Fusing 732C ; Softening 663C ; Annealing 538C ; Strain 427C

This listing also shows that the temperature characteristics are not linear between glasses. For example, Spectrum and Uroboros have the same full fuse temperatures, but different tack fusing, softening, annealing and strain temperatures. Sometimes one is higher than the other, and other times it is reversed.

Another example is shown by the Desag GNA and Float glasses. Desag GNA has higher full fuse and tack fuse temperatures than float, but lower softening, annealing and strain temperatures. This helps to make the point that you need to know the glass you are using as it will not have a proportional relationship at every point in the kiln working temperature range.

I emphasise that these temperatures have been collected over a period and may not be the current or absolutely correct information. They are used here to illustrate the differences within and between the glasses of various manufacturers.