Wednesday, 29 June 2016

Kiln Forming Myths 26 - Fast Ramps

Firing AFAP harms your kiln.

This may be a hangover from the time when ceramic kilns were being used commonly.  There certainly is a tradition of this kind in ceramics practice.  However, nowadays we are firing in kilns with light weight bricks or fibre, or a combination of the two, making this less relevant.

The light weight bricks are much less subject to temperature shock than the dense ones.  Fibre is completely unaffected by rapid changes in temperature.

Firing as fast as possible is much more likely to damage the glass you have in the kiln than the kiln itself.  It is also likely to have over runs in temperature.  The controllers compare the actual increase in temperature with that requested by the schedule.  It takes time for the controller to “learn” the rate of advance being achieved within the kiln.  On fast rises in temperature, it does not have the capacity to stop the input of energy early enough to prevent the kiln temperature rising beyond that which is programmed.  This can lead to unexpected and unexplained results (unless you think about the effects of an AFAP rate on the controller's computer).