Pot Melt Temperature Effects

Image credit: Craft Gossip

When firing a pot melt, you have to consider how high a temperature is needed.

Viscosity reduces with higher temperatures which increases the flow and reduces the length of soak, although there are often some undesirable opacifying effects at prolonged higher temperatures.

The size of the hole is also relevant to the temperature chosen. The smaller the hole, the higher the temperature will have to be to empty the pot in the same amount of time. Of course, you can just soak for longer at a lower temperature to achieve the desired object of emptying of the pot without changing the temperature.

Using the same principle, the larger the hole the lower the temperature required to empty the pot in a given amount of time.  So, in general the larger the hole in the pot, the faster it will empty, given the same temperature.

The temperature used to empty the pot will need to be between 840C and 925C (1546F and 1700F).  The problem with temperatures in the 900C to 925C range is that the hot colours tend to change, e.g., red opal tends to turn dark and sometimes become brown. Some transparent hot colour glasses also opacify. There is also the possibility that some of these glasses will change their compatibility with others in the range.

The best results seem to come from temperatures in the 840 to 850C range with longer soaks than would be required at 925C.  Also remember to give melts a longer than usual anneal as they will be thicker than 6mm at the centre - sometimes as  twice the edge thickness, which will require annealing for twice the thickest area.

Revised 2.1.25