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suitable flint?

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Chippintuff:
Raalf, good pictures of stone show a lot about it's chippability. If you can post some photos of the rock where it has been broken, we can tell you pretty close to it's potential.

Most of the rock that breaks leaving a grainy surface is not good for knapping and may be impossible to knap. As a general rule, the slicker the flake surfaces/scars are, the greater the potential for knapping. Take a big rock or a hammer and hit one of them hard enough to crack it open and post a photo.

WA

raalf:
oh please look at my rock

Zuma:
Do you the  see  the white stuff on top? That's cortex/rind.
If your finds did not have that completely encompassing
the chert/flint it may have been recently mined or disturbed.
It looks like good lens flint that has many inclusions due to tectonics
or frost.
You need to isolate chunks that have no inclusions to get some
good smaller points or get lucky to find a bigger piece clear of
(pre cracks).
Zuma

mullet:
I'd take pieces of that and try heating it again. If 400 dgs didn't work I'd go up a hundred Dgs at a time till I found a temperature that did. Looking at he picture that rock should make some points. It looks similar to Danish Flint but with more inclusions.

Chippintuff:
I agree. That rock looks pretty difficult. Heat will almost certainly improve it's knapping characteristics. Like Mullet said, I would go to 400*F on the first cooking. For my chipping, I set the second cooking relative to the change seen (or not seen) in the first cooking. If it flakes better (slicker and with less force) but not good enough, I jump it up 50*F on the next cooking. If there is no change, I jump it up 100*F. I repeat this process till I get reasonably knappable rock or till I max out my cooker.

Do you know anything about cooking rocks? It is a skill that usually takes some practice and input from other knappers. I use a turkey roaster ($25.00 cost). As it comes from the store, it will take rock to 450*F or a little higher. With some tweaking (insulation etc.) I have gotten up to 550*F or higher.

If you take the temp up too fast, the rocks will explode because there is water in all of them, and it turns to steam as soon as the rock goes above 212*F. Cook them at about 190*F-200*F overnight and then start ramping the temp up by 50*F-100*F per hour till the desired temp is reached. Hold it at the desired temp for 2 hrs-24 or more hrs. Two hours will affect the knappability, but longer cook times may also change the color of some rock.

If you ever hear a dull bump inside the cooker, you are taking it up too fast. They are blowing up. Turn the heat down, but do not open the cooker while it is hot.

Bring your questions here, and we can help.

WA

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