Primitive Archer
Main Discussion Area => Flintknapping => Topic started by: bushman on July 31, 2011, 08:30:18 pm
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How do you guys go about removing a turtle back?
Bushman
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I remove mass from both sides with percussion & then prepare a platform & remove the remaining percussion bulb. Repeat if necessary. That's how I do it. Others may use another method.
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I work it from the ends, or where the natural ridges of the rock are. It is easier to follow those ridges, than to run removal flakes through them. well, it works for me anyway.
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The problem I had (with turtles) when i was first starting was worrying about loosing material. nowadays when I have one of them I just go at it. Don't be afraid to sacrifice some length or width to set up a good strong angle and hit it high on the margin to remove mass as quickly as you can.
All good advice above.
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so.....whats a turtle back
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Guessing the percussion bulb from the spall flake?
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I was thinking it looked like this. This is an artifact found on a farm nearby.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-07-31224011.jpg)
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I think the platform on the right failed and maybe they gave up.
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What the h{\\ is that thing! Guess I need to get out of the house more often.
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I show you more photo in 4 minutes
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(http://i1131.photobucket.com/albums/m559/iowabow2/1312170692359.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/1312170759472.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/1312170726287.jpg)
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Is it a failed attempt by one of our knapping forefathers? Or a tool fashioned from a percussion bulb by one of the ancients? Can't really tell.
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Sure could be. Do you think this is what they mean when they say "turtle back".
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that is pretty much a turtle back. Usually flat on one side and the other side very pronounced. Normally in smaller rocks. They get pitched to the side alot. They can be a handful to deal with.
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How would you guys go about removing flakes from the hump side of a rock or spall like is in the pictures that iowabow posted (Thanks iowabow for the pictures, that’s what I was talking about, just didn’t have any pictures to show it that good.) How do you set up your platforms, extra? If you get a flake that is a turtle back is there any way to remove it and still make a point out of it? Every time I try it all I get is a smaller turtle back, or end up with a bird point. Thanks
Bushman
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Build a strong, steep platform below the center line on the humped side and take off some deep flakes. You'll lose some length or width, but if you don't back flake to move the platform way down on the humped side and get the mass off, you'll just keep reinforcing the turtleback.
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Just noticed that hillbilly had the same idea I had, only I went the other way. :laugh: What he said, and you can get that mass off. Here is the way I would attack it.
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I like to build some convexity on the flat side an thismoves your center line closer to the hump side, Then get agressive when you go after the hump >:( >:( >:(
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Real hard to explain. There is a great video that is sold at three rivers archey of a guy that flint knaps in a cabin and shows you how to keep both ends from reducing size. His name starts with an H. I will be knapping tomorrow and I will look for the worst turtle back I have and post here the process including failure or success. I normally save them for when I get to the end of my supply.
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I used to have a great video on square edges an turtlebacks, I believe Mike Santiago and Mark Bracken did the video. Now if I could only remember who I lent it too. :o ??? ???
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Ok I pick the worst stone I could. This piece was not heat treated and has some frost cracks on it.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02085302.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02085240.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02085600.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02085700.jpg)
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(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02090113.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02090302.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02090842.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02090947.jpg)
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I shot five more flake off that ridge from the same direction. This what it looks like now. I am working the ridge so I can run long flake off later.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02091808.jpg)
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Setting up a reverse platform.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02091859.jpg)
You can see in this picture 2 sides that offer now platfroms.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02091943.jpg)
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I then start removing ridge flakes this is were we will lose the frst deal on the end.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02092129.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02092659.jpg)
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Everything going well and even the frost came off clean with this flake. So this is where I am at for now. I will post more as the project continues. I took 35 pictures that is how many times I have hit this stone removing flakes.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02093113.jpg)
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Well the thinning went well yeilding some useable flakes for small points if the turtle flops. I like how the light goes through this material. I am kinda hoping now that a point can be made from this rock. The bottom has not been cleaned up and has cracks. The plan is to remove a couple more from the turtle side then clean up the bottom and then start making the point. It is still a long ways from being a point.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02110240.jpg)
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Ok here are the rest
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02123657.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02113526.jpg)
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(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02134534.jpg)
Thought I was crazy because no matter what I did I could not get that step out. You will see why later.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02141439.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02150425.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02153240.jpg)
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Well I finally got that concrete and it made me try a new form.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02153240.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02154126.jpg)
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Ok last two pictures but thats kinda how I handle turtle backs with junk in the trunk. I don't work them normally because they are hard. I started this at 8am and it is 4pm now I took a 2 hour break.
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02154543-1.jpg)
(http://i1131.photobucket.com/albums/m559/iowabow2/2011-08-02154828.jpg)
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Great job on a tough piece. Some of those long flakes would make good gun flints.
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I I have not seen any gun flints. Do they break them in half and the flake one end?
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Here's how I do it. ;D
http://www.youtube.com/watch?v=5P-1edaal18
http://www.youtube.com/watch?v=EUcm8lD0Rm4
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That is to cool that you can knap like that jack.
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Thanks Iowa. My flintknapping buddies out here gave me some funny looks at first but they are used to seeing it now. :o ;D
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I just doesn't look like it should work. I tried one day to do it after watching your video and it was a nogo for me. I think I am going to have to see it in person. You however make it work amazingly well.
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Watch my video "A Different Perspective" to get a view of my technique from a distance.
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i want to chime in on strategy for turtlebacks- preforms with one flatter side and one humped side. The humped side is difficult to thin. conventional wisdom says that this is a problem of centerline- it's hard to thin the humpped side because the edge is so far "above" center ( a "high" edge, when viewed with the humpped side facing down). therefore you could move the edge toward center , letting you get at the humped side. (others above suggested this) BUT- this sacrifices length and width fast. Therefore, I try to use massive percussion flakes to thin the hump with only one or two flakes which come off this "high" edge. It's kinda like a deep overshot flake. you have to set up steep strong platforms and give them a mighty whack- hard to do on smaller pieces, but i work in easy obsidian. I think this is illustrated by the pic above in timo's post where he drew a platform on that artifact photo.
to state this another way- I just ignore the rule which says platforms should be near or below the centerline. The flake wants to hinge as it dives into the hump, but with enough oomph and support, it can lead to some nice rapid thinning.
i didn't watch jackcraftys whole vid, so sorry if this is covered there...(cool technique, though !)
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Thanks for all of the help everyone, it has helped a lot. Thank you iowabow for taking the time to take all of them pictures to show the process and for posting them, was that a piece of coral?
Bushman
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No it was a piece of flint burlington.
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I just doesn't look like it should work. I tried one day to do it after watching your video and it was a nogo for me. I think I am going to have to see it in person. You however make it work amazingly well.
I learned from Patrick so I use his indirect percussion method too. Even sitting with him, I really struggled with the technique at first. It took the better part of 2 days to begin to "get it" so to speak. The hardest thing for me was understanding how hard I needed to hit that thing to run a long flake. I've finally ordered some plastic bars to make duplicates of his. Hardwood just will not take the bashing. Since I have a small wire in one end of the tool I do almost no pressure flaking except to sharpen and notch the point. That's the next thing I need to learn. I think my problem with turtle backs is that I don't do enough platform prep, especially abraiding, so I get the big flake when I go for it. If the preform is relatively small, and most of mine are, I only get a couple of attempts at knocking the hump off before the point is too narrow or too short. It is definitely easier to do with direct percussion, but if I miss a little bit I sometimes ruin the point. I hate it when that happens.
Good thread.
George
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I think working a turtle back takes time and material. The more you work at it the better you get. Everyday I get better because of what I learn from the last point.