[Sca-cooks] Charcoal forge suggestion ;-)

[marilyn traber 011221]

> The cuplrit in this case was moisture... 
> since you were unevenly heating the terra cotta pottery (which is 
> usually unfired clay) any moisture in the aggregate will go to steam 
> unevenly and the internal pressure, along with the thermal stress, 
> will crack such a pot every time. 
> 
> Try removing the moisture by placing the pottery in a 220 degree 
> oven overnight. then in the morning turn the heat up to 500 degrees 
> for a couple of hours to "set" the pot. That should manage to 
> protect your pot soemwhat. 
> (it still neads to be heated evenly and slowly or thermal stress 
> will crack it, but it helps on the moisture front) The problem is 
> going to be that if the pot is heated evenly enough to prevent 
> thermal stress cracking it, it will also be hot enough on the bottom 
> to damage what it is set on anyway, so perhaps your best bet is to 
> use a pot in conjunction with an insulating surface, such as a 
> sacrifical wood plank, or anothe clay tile, or a metal trivet. 
> 
> Perhaps a better alternative is to line the pot with an inch or so 
> of slighly moist sand. 
> 
> Capt Elias

Thank you, Brandu, for an excellent explanation. I was avoiding going into 
details, because this is SCA-Cooks List, not EKMetalsmiths ;-) but, since 
he'd asked, was going to go into detail, and you saved me the trouble.

Stefan, the reason that modern high- temp ceramics are completely glazed is 
to prevent moisture from wandering into the clay. A flower pot, and, for that 
matter, the unglazed clay cookpots like rommertopfs are designed to soak up 
water and release it slowly for the benefit of the contents. That's NOT what 
you want happening when you're using high temperatures with melting metals.

Stefan think- what temperatures are the standard flower pots exposed to? And 
what temps are you getting to, to melt your pewter, whether modern lead-free, 
or old fasioned leaded? And, what would happen if you poured a glass of water 
onto your melted pewter?

Drakey, DON'T try this to find out!!!!!!!!!!!!

Saint Phlip,
CoD

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