Kiln Firing Schedule for Kiln Carving

This generic kiln firing schedule for kiln carving is to be treated with kiln firing schedule caution – be warned! There are so many different variables; not just with the kiln itself (eg. size, where the elements are situated, insulation properties) but also with the glass (eg. type, thickness, inclusions, pre-fusing). The schedule below is to be taken as a starting point for your own experiments – not a recipe for instant success. By the same token, I can’t be held responsible for any glass disasters you have following this firing schedule . Sorry - I’ve had too many all of my own!

So what exactly is kiln carving?

kiln firing schedule It describes the process by which you slowly melt glass into a shallow mould so that it picks up the shape or texture of that mould. Whether that mould is made of ceramic fibre paper, plaster of paris or clay is immaterial - the crucial difference between glass slumping and kiln carving is the detail and depth. Slumping glass is when you shape glass into a smooth bowl mould which can be quite deep, whereas kiln carving allows for much more detail in shallow relief.
The glass kiln firing schedule below is calculated for two 3mm layers of Bullseye glass that have been pre-fused. Check the annealing temperatures for the glass you’re using and adjust accordingly. The cycle lasts for approximately 18 hours, so be prepared to bite your nails over a long period…

An Example of a Generic Kiln Firing Schedule

Segment	Rate Degrees C	Temp	Soak (Hold)	Additional Notes
1	110	480	15-20	Primal heat up. Taken slowly so that you don’t shock the glass. Slow down further if you have any inclusions, if glass is next to elements. Vent a kiln at this stage, to burn off glue and other organic material.
2	280	595	-	Moving from Primal to Forming stage. Glass unlikely to thermally shock at this range, but do be cautious – if your glass is thicker, or contains any element that interferes with even heating, slow the rate of this segment down.
3	55	677	30	The slow rate up during this segment and the 30min soak is known as the ‘bubble squeeze’. It allows the glass to settle together, and reduces the chance of bubbles. If you want to encourage bubbles, you can remove this section.
4	full (9999)	835	20	Moving into the liquid stage. To avoid devitrification (crystals forming on the surface of the glass) ramp up to top temp. as fast as possible. There are many alternatives to this approach – e.g. using heat work during the ramp up, which means going up slower and holding at a lower top temp. Use the kiiln firing schedule that’s right for your project. The 20min soak allows the slumping glass to take the form of the glass fusing molds it’s resting on. Ajust accordingly.
5	full (9999)	515	60	It’s now time for the quick descent into the annealing range. It’s generally agreed that whizzing down as fast as possible from the top temp. to the start of the annealing stage is crucial. The 60 min hold allows the molecules in the glass to realign and the temperature throughout the glass to equalise.
6	28	426	-	Now a slow cool through the annealing range. The glass contracts and hardens evenly so that it can return to a secure solid state. This is the time when any incompatibilities in the fused glass are exposed – the rate of contraction is different and the glass will crack.
7	55	371	-	This segment finishes off the annealing safely.
8	166	38	end	Take the glass down to room temperature. You can slow this section of the kiln firing schedule down if there are any elements in your glass that could contribute to thermal shock. Don’t open until it’s at room temp, however tempting!!!