Mostly for Outback Bob who wanted info on Flint River.
Not menaing your cheap Bob
In my experience an oven is all you need to heat most common cherts and even the dry splintery green obsidian. I'm cheap when it comes to energy consumption.
So I may be pushing things a little but I think I have a pretty satisfactory method.
500 degrees is all you need. To protect the oven I put the material in a large
covered pan and raise the heat 50 degrees at a time with an hour interval.
Start at a moisture burn off temp of 175 with lid off and oven door cracked open. Place lid on after you think things are dry. LOL good luck here.
When you reach 500 let soak an hour or so before reversing process back to 300-250 for an hour then shut down.
Let cool for at least 6 hrs. I have never had a problem especially when I cover the
material with sand so that no two pieces touch, (layers also)
Material reduced to preform size works best. Bigger pieces can be heated
knapped or slabbed then heated again. I have treated all these materials the same way--
English, Edwards, VA jasper, Flint River, some MO cherts and the Green obsidian.
Some failures I have had is where there is (jasper and English) course and
high quality in the same hunk. It seems the high quality ( very waxy more translucent) areas tend to craze while the rougher stuff improves.
Hope that helps.
Zuma
