Go-to Schedules

 It’s a schedule I always use.

This is a frequent statement in response to a firing that has gone wrong.

You don't always fuse the same thing, or the same design, or the same thickness, etc. So why always use the same schedule?

The schedule for the firing each piece needs to be assessed individually. It may be similar to previous firings. But it may have differences. Assess what those differences mean for the firing.  Some factors to consider.

Addition of another layer to a stack in tack fusing makes a difference to the firing requirements. Even if it is only on part of the piece. It needs to have a slower ramp rate and a longer anneal soak and slower cooling.

A different design will make a difference in firing requirements too. For example, if you are adding a design to the edges of the glass, you will need different bubble squeeze schedules than when you do not have a border. It will need to be slower and longer than usual.

The placement of the piece in the kiln may require a re-think of the schedule too. If the piece is near the edge of the kiln shelf, or in a cool part of the kiln while others are more central, the same schedule is unlikely to work. You need to slow the schedule to account for the different heat work each piece will receive during the firing.

If you have introduced a strong contrast of colour or mixed transparent and opalescent glass in a different way, you may need slower heat ups and longer cools.

These are some examples of why the same schedule does not work all the time. It works for pieces that are the same. But it does not work for pieces that are different. And we should not expect it to.

There are sources to help in developing appropriate schedules. Bob Leatherbarrow’s book FiringSchedules for Kilnformed Glass is an excellent one.

Another one is especially good for lower temperature work: Low Temperature Kilnforming, anEvidence-Based Approach to Scheduling. Be aware that I have a vested interest here – I wrote it.