No I remember reading an article from the old Fllintknappers exchange or the Tarp that was describing the same conditions and the gist of the article was that it had stresses in it and the heating relieved the stress. I would think you could go pretty high with maybe 500, take notes and let us know.
Well Steve,
I cranked these spalls up to 450 for a test 50 degrees every hour or so.
I let them soak an hour. Dropped back to 300 at 50 an hour.
Turned off the heat and let cool overnight.
Thanks to your advice I think I have plenty of good knapping for a long
a time to come.
The best part is getting a decent ground platform is now possible.
Still a little splintery where the spall I knapped seperated from the
mother ship.