Wednesday, 25 March 2020

Scheduling to Room Temperature

Why Schedule the kiln to room temperature? The kiln will cool slowly enough at the final stages.

How do you know?

Relatively large thick pieces need slow rates of cooling below 370°C.  Complex tack fused pieces require slow cooling rates as well as the long annealing soaks. These required rates of cooling may be slower than your kiln’s unpowered rate of cooling.

This means you need to know the natural cooling rate of your kiln from 370°C down to room temperature to be sure you are cooling at a suitable rate. The method described in this blog post gives you information on how to calculate the natural cooling rate of your kiln.

I program my firings to about twice room temperature. Yes, the kiln does not turn on much during that time,  but when I crack my kiln open to speed the cooling, the switching on of the relay tells me I am cooling faster than programmed, and I can reduce the size of the opening to avoid too rapid cooling of the piece.

The following chart is a way to assist in recording your kiln’s unassisted cooling temperatures against time to give you the natural cooling rate at various temperatures.

Natural Cooling Rate of the Kiln

Kiln Name: Cooling Rate
observ'n Time (hr:min) Temperature Difference rate/min  rate/hr 
1         : Time (mins) Temp. =temp/mins .=temp/min*60
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