Following on from the discussion on re-firing and cracks...........

I've tried to convert the below ramp from deg F to deg C, and calculate how long the firing will take. (Theory of course, I know the kiln may not be able to keep up/down with the ramp rate, but it will give me a guide as to firing time.

Cone 6 Glaze Firing

100 degrees F per hour to 220 degrees F, no hold

350 degrees F per hour to 2000 degrees F, no hold

150 degrees F per hour to 2185 degrees F, hold 15 minutes

On the way down:

500 degrees F per hour to 1900 degrees F, no hold

125 to 175 degrees F per hour to 1450 degrees F, no hold

Cool naturally from 1450 degrees F

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The maths on both sides looks OK. I converted the deg F to deg C using the Excel Convert formula, and double-checked the results using online conversion sites, so they are correct. But the results to work out time taken don't make sense. I used (EndTemp-StartTemp)/Ramp, looking at degF and degC separately, the results look sensible, but I would expect them to be the **same **as each other.

So, why does firing in Deg C takes longer than firing in Deg F. I don't believe in Santa Claus, and I don't believe these figures either.

Can anyone throw any light on this?