Pots
During this firing, we lost almost two pots a day. We tried upending them in the stoke hole to cool down slowly overnight, but this did not work! The reason for the pots breaking (usually at the glass line) is that as the glass cools down below 500°C it shrinks more than the pot, putting the pot under stress.

Autumn 2021 update: We have now found a small second-hand electric kiln to keep the pots warm overnight. This should be installed by Firing Five in 2022.

Various combinations of pots and positions were tried, and it was clear that this was a very versatile furnace. The shelves were too low, and do need to be increased in height by about three inches. The pots were supported by bricks and other refractory offcuts, which made balancing them securely rather tricky! We will use the other new shelves on top of those already in position and add spacers to bring them up to the required height.

We also made a support for the small pots containing coloured glass. This initially worked, and did survive through the entire firing, but the fired daub we used was not stable at glassblowing temperatures and distorted and eventually broke (not helped by the thermal shock of cooling down each night).

Collars
This was a success story. We continued to fire the new collars and stoppers to 1000°C, and their survival rate was impressive - a couple cracked, but we have discovered that we can stick them together with high temperature sealant. We also painted the hot faces of the ones that would be in place for long periods of time with zircon silicate slip for added protection from the furnace atmosphere and the molten glass.