Firing the PrattMWP salt kiln- some notes...

Our salt kiln is built mostly out of k23 and k26 insulating fire brick.  Although this type of brick is susceptible to faster deterioration,  coatings or not, we feel that the time and fuel savings are enough to warrant using them.  From a teaching standpoint, the ability to fire our kilns using a shorter schedule is especially helpful in a continuing education setting.  Our students do not always have the time to tend a kiln for 24 hours.  There is no need for this anyway.  A good firing schedule does not have to be long- just set up for a safe and and successful outcome.  A good steady ramp and knowledge of some basic elements that impact ceramic materials are needed.  

Over the next few posts we will discuss heat gain or ramping and controlling of the kiln atmosphere.  These are easy to describe but nothing improves firing skills more than experience, trial and error. Learn to read the kiln.  Take good notes.   Pay close attention to cause and effects.  Lectures or written instructions are a good start but never a substitute for doing and seeing.  You fire with the senses!  All the pyrometers and Co2 analyzers will not take the place of using your eyes, ears and nose.  Weather is often questioned as a factor.  It is to some extent.  Barometric pressure can have its effects.  Outside temperature is of no consequence.  For this discussion, we will assume the kiln is protected from the most problematic of weather conditions, the wind.  


We fire our salt kiln with natural gas. Some other time we can get into the differences between fuels.  Most potters use natural gas, propane or wood.  Oil is still used, but it seems rare.  Still, the basic ideas we will talk about are the same regardless of fuel.    


One last thing-  your head should be inside the kiln!  Some of the reads are "external" but they are symptoms of the atmosphere in the chamber, surrounding the pots.  And the reads will be different from kiln to kiln.  They can also be different from firing to firing.  Good notes and kiln logs will help in seeing  the nuances and effects of loading patterns and kiln designs.  This stuff is amazing.  How nature applies its laws to the firing and how materials react to heat, oxygen and carbon, we might take for granted.  Over the years one can lose the mystical sense of any firing.  But it is sheer poetry (in motion!).  It isn't the outcome.  It is the input.  Good craic(!) as they say in Ireland.