suitable flint?

[raalf]

a few months ago i got into my head that i needed to be able to make stone tools like my ancestors did 5000 years ago

i live in a river delta, called the netherlands in western europe, on a big heap of sand. the only place the bedrock comes through the sand is 30 miles southwards, near maastricht. there are some prehistoric flint mines found there.
i found a local limestone quarry that encounters blobs of flint. i took a wheelbarrow full of it home.

i tried knapping it with some hammerstones and copper hamers, but i can't get flakes off that are longer then 1 inch.
I tried heat treating, in an oven for 24 hours at 400 degrees fahrenheit

all the youtube video's I see people spalling flakes of multiple inches long.
what should I do? find another source of flint? do different heat treatment?

[RickB]

Here's a free online reference that may answer many of your questions - hope it will help out. Rick B

http://flintknappinginfo.webstarts.com/uploads/Online_Flintknapping_Articles9-30-11.pdf

[Zuma]

Perhaps some photos could help.
If your platform is incorrect small spalls may be all you get.
How sharp are the edges do you have a 130 o/o cleavage?
Zuma
btw welcome to PA

[mullet]

Let's see some pictures of the rock.

[JerseyBill]

Here's a free online reference that may answer many of your questions - hope it will help out. Rick B

http://flintknappinginfo.webstarts.com/uploads/Online_Flintknapping_Articles9-30-11.pdf

Many thanks for this link Rick. Like Raalf my interest is in the Neolithic and the collection of articles looks like being gold dust.

Have only just joined the Forum - and am delighted and astonished at the knowledge you guys share so freely and in the true spirit of cooperation. Thanks to you all! 

[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

[raalf]

Okay, gonna try cooking some more.

I have a programmable industrial oven at work I can use.
Sounds like popcorn when cooking, when I put them in naked.
Will use some sand this time to slow down the process.

[Chippintuff]

Some use sand, and some never use it. I use it because I think it reduces the chance of the temperature changing too fast. If I heard "popcorn" inside my cooker, it would be rocks fracturing.

Some say they cook whole rocks without problems, but in my experience it has been best to thin it to about an inch thick or less before cooking it.

WA

[mullet]

For all of my smaller stuff I use a Black and Decker toaster oven. I've bought two at the Flea market for $5 a piece. It goes up to 550dgs. I just stack as much rock as possible inside, turn it to 450-500 and let it go all night. I unplug it in the morning and take the rock out when I get home from work. I've never ramped it up in stages but I don't cook large pieces in it. You can also bury it in dry sand about 2-3" and set a large bag of charcoal on it and let it burn till it is cool enough to dig the rock up.

[Chippintuff]

Eddie, I would have never thought a toaster oven used like that would work, but if it does, it does. I have an old toaster oven that works fine but is showing a lot of use. That may be a good experiment for it. Does it cook evenly throughout the batch?

WA

[mullet]

Yes it does. The only time I have any pop is when I mix Perdanales with a harder chert and it gets too hot. Now I try to just cook rock that needs to heat treat around the same temperature. Most of the time it is small spalls but occasionally I'll put bigger ones in to help reducing them down during thinning when it starts to get tough again.