Annealing temperatures by colour

 It has been suggested that there are different annealing temperatures for different colour groups. This is not so.

All the colours in a single fusing compatible range are annealed at the same temperature. It is true that there are variations in the viscosities of different colours, but these are designed by the makers to be minor. Also relevant is that annealing can occur over a range, making concern about different viscosities within a fusing compatible line of glass less important. The anneal soak gives time for all the glass to reach the same temperature differential of ∆T = 5°C, where the viscosity differences will be so small as to be insignificant.

There are precautions that should be observed when combining strongly contrasting colours or contrasting styles. In general, hot and dark colours are less viscous than light and cool colours at slumping and above temperatures. There are also contrasting viscosities between opalescent and transparent colours. A cautious approach to these differences in viscosities is to anneal them as for one layer thicker than that for the profile of the finished item.

The annealing temperature remains the same for all the glass in a fusing compatible line, regardless of colour or style. The length of the anneal soak and cool rates may be altered for these contrasts, but not the anneal temperature.