1971: "Investigations concerning the thermal alteration of silica minerals"

[Chippintuff]

If the beneficial effect is due to merely the reduction in moisture in the stone, why does some stone require higher temps? Why can't they all be treated effectively at 250 F? If the stone has been cooked a little too hot or too long, what is to prevent soaking it in water to restore it's raw state, assuming that internal fractures have not been made. I think he did mention that cooked stone eventually returns to the raw state. If that is so, why not cook the stone, flake it, then soak it in water to restore it's original durability?

WA

[Dalton Knapper]

Agreed - some people swear by using soaked stone or stone fresh from the ground because it knapps more easily than dried out raw stone. I have heard heat treating may break the microcrystalline bonds to a degree, hence heat treating works.

[JackCrafty]

Good points Chippin.  I've got stuff that I heat treated 3 years ago and it's sitting on the ground getting wet from our sprinkler system every day.  It still knaps the same whever a grab a piece from the pile.  A patina has developed on most of the material but I see no reason to believe water has anything to do with the heat treating process... that's why I think the idea is surprising.  Experience tells me that the rock gets weaker from heat and never recovers.

[caveman2533]

Its not just a reduction in moisture its a "compaction" of the crystals. Compaction not being the word I really want. It is actually removed on a molecular level from the spaces between the crystals and causes them to be tighter.  My rock and mineral club had a geologist speaking one night and he was discussing crystal structure and how water affected cyrstal growth and  when it was removed it somehow broke the bonds or .... It was very confusing and most people were pretty lost.  I would like to contact him as he does not live far from me and talk to him more about it. He was retired and  very passionate about his work.

[Ghost Knapper]

A good explanation of two possible theories on heat treating can be found in "The Art of Flintknapping".

Short Versions:

Purdy/Brooks Theory- "..claim that the matrix of impurities around the quartz crystals melts and reforms into a denser material that holds the crystals more firmly..." "This would permit the shock waves to travel not only around but through the crystals as well". -D.C. Waldorf

Flenniken/Garrison- "...instead of reforming the matrix the heat causes micro fracturing of both matrix and crystals..." "...being of different composition the matrix and crystals expand at different rates causing the micro fractures..." -D.C. Waldorf

One group was using florida cherts the other novaculite so both theories could be right. The above information is in Chapter 2 (page 9 in the fifth edition)

[Zuma]

Quote from Ben's info

" NOT ONE OF THESE ARTIFACTS APPEARS TO HAVE BEEN INTENTIONALLY HEAT TREATED. Judging from the large numbers of unfluted, but potentially Early Paleoindian stage 2 and 3 bifaces recovered from the site, all stages of point production are well represented in this local RAW MATERIAL."

This includes HUNDREDS of Paleoindian artifacts (PAGE 3).  This also includes 224 fluted biface rejects (PAGE 4)"

Ben---To bad you don't show the INTENTIONAL OVERSHOT Clovis RAW material from this site.
If these dudes knew your secret, why so many failures??
Please respond with coherent, honest answers.   Especially about your failures in raw chert.