[Stoves] Crispin´s kiln-was Re: Traditional Charcoal Making

[Crispin Pemberton-Pigott]

Dear Jeff

You have a point at least to be considered.  If you made the inside
reflective, would the heat put back onto the parts already hottest make the
problem worse?  What about the reflective coating separating from the
brickwork?  Generally the kiln bricks have a pretty low thermal expansion
coefficient.  The coating would have to match it or it would separate pretty
quickly.

The normal method of handling the problem is to use a muffle furnace - one
that has a sheet of ceramic material between the element and the 'work'.
The whole sheet gets hot instead of just the concentrated heat
radiating/conducting from the element which is perhaps 10 or 20% of the
area.  That is why an arc would make things worse - further concentrating
the heat source makes heat distribution harder.

The materials development workshop actually uses muffle furnaces but they
are far more expensive and usually, in the lab, much smaller so cost is not
such an issue.

As David L pointed out, the convection brings down the heating time
dramatically so the question to be answered is, can the gas furnace provide
the right kind of circulation through the necessity of passing gases in one
end and out the other?

Perhaps the answer can be provided by looking at conventional gas ovens for
the home.  Are they a working example of good convection?

Regards
Crispin

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Jeff Davis
Subject: Re: [Stoves] Crispin´s kiln-was Re: Traditional Charcoal Making

Crispin wrote:
> Re the glaze - anything that reduces the temperature gap between those
> parts that face the elements and those that don't is welcome!

OK, I'm thinking/seeing shadows. ...... So maybe the inside of the kiln
should be reflective.