[Stoves] Crispin´s kiln. (was Re: Traditonal Charcola Making Process / retort

[Crispin Pemberton-Pigott]

Dear Friends

In a message on 7 July (07-07-07)
> 
> Also one of Crispin's dilemmas was the way heat was delivered by the 
> resistance heaters, I suspect one of the reasons for the slow ramp ups 
> is to avoid thermal shock but at the end temperature, which is where 
> 30% of the power is used, the reason could be to avoid the hotter 
> parts of the oven overcooking the bodies there while the bodies at the 
> cooler part heat up.

The main reason os not thermal shock, though that was a good guess.  The
kiln won't heat up fast enough to generate a thermal shock.  The main
problem is direct, radiative heating of the stoves.  If they are near the
elements, they melt.

>The raw stoves have significant quantities of water content. 
>Excessive heating rate can seal the surface of the stove 
>bodies while there is still free or bound water within the clay.

This has not been such a big problem, but trapping charcoal inside
definitely has.  The charcoal has to be burned out or else is swells like a
balloon later on, about 900 I think.

Regards
Crispin