Firing Small Pieces

 Do you run small pieces of glass through the whole cycle or just bring it up to your degree posted and cool down?

 

Picture credit: Eva Glass Design

It would appear easy to ignore the need to anneal small pieces.  They can anneal with short heat soaks.  In industry the anneal of sheet glass is 15 minutes for 4mm/0.019” glass.   In kilnforming the 30ºC - 40ºC/54ºF – 72ºF below the annealing point is where annealing is effective.  If you are certain that the natural cooling rate of your kiln is more than 15 minutes for that temperature range, you can simply turn off after top temperature.

However, it is not a good practice unless you intend to confine you kilnforming to small pieces.  All glass needs to be annealed to be sound.  Small pieces may need only 15 minutes and often that can be achieved with the natural cooling rate of your kiln.  But pieces of 6mm/0.25” thick and over 100mm/4” in any direction need to be annealed with longer soaks and slower cools.  This is done with a hold of the amount of time appropriate to your glass and layup.  There is an excellent table from Bullseye that gives the hold times and rates for cooling glass of different calculated thickness. 

Using an annealing soak and a cooling cycle for every firing is a good practice.  This gets you into a habit, so that you do not skimp on the anneal and cool for larger, thicker, or tack fused pieces.  If your kiln cools more slowly than you have scheduled, that's ok.  The kiln does not use any electricity to heat the elements.  No additional electricity cost or wear on the kiln occurs.