Making Knifes from Obsidian slabs?

[warhawk]

 I bought obsidian in Mahogany, royal purple and leopardskin. It was precut into 4/8 inch thickness i need to find out how to thin it without breaking it or thinning it into very a narrow knife. I have experimented with 3in by 1 1/2 inch wide pieces and i have broken 2 in half already. so lets the knowledge follow because i am listening.

[mullet]

 Diamond saw and diamond grinder.

[Bill Skinner]

Rigid palm pad with 3/8th groove.  X the edge by starting at one corner, take a thick flake, turn the slab over and take another thick flake.  Work the entire side, flip it over and do the same to the other side.  Abrade heavily, useing your Ishi stick and the rigid pad, pop flakes off by setting the tip and squeezing with knees, lean into it and then pop your wrist.  The flake will follow the groove in the pad.  If you did it right, you should have gotten a flake to the center of your slab.  Now you have a ridge, your next flake will come off parallel to the 1st.  Once you get it "skinned" it is nothing but pressure flaking.  Watch your tip and base, you can end snap them with a pressure flaker.  Some people skin first then X, both ways will work.  The pad must be rigid, one of mine is oak with leather glued on top, the other is lexan with two chunks of conveyer belt.   Bill 

[warhawk]

thank you very much Mr Skinner. I truly believe that all knapper need to encourage each of us to better perfect our abilities and i wish that other knappers on this website would answer theses questions that are displayed for public attention and even the masters should remember that we all love to knapp some rock and bring out the artifact that is inside the stone.

[mullet]

  Sorry, warhawk, I've been busy as all get out at work. And am truley not one of the Masters. I was trying to keep your question to the top till somebody was worthy enough to answer you question. 

[cowboy]

warhawk: I worked a few obs slabs several years ago. They were 1/4" thick by about 2" wide and averaged around 5 or 6 inches long. Way I did it was to rough up along the edge your going to work with abrader just enough for the ishi to grab ahold of it. Don't touch that edge once it's roughed up because the oils from you skin will cause the ishi to slip. I was starting at the base working to the tip. Grab about a quarter of the thickness down with the ishi and pop off long flakes at least to center, repeat other side, then flip it over and do the same to those two sides. Once that's complete it's a lot of flipping back and forth stitching those edges to get it sharp, then your done.
  Those blades turned out pretty nice (the ones I didn't break that is) but I found more satisfaction in bopping and pressure flaking the rough rocks.

[mullet]

  Another way than what Cowboy is doing; is to rough the edge, and run flakes a quarter of the way. Then come back and ground the top of the slab, (short flake run) rounding it off (ovate). Then gound the edge at a slight angle and then pressure flake to the center. Repeat the other side. Then come back and stich the edge. Then, come back with a horse shoe nail, or very fine, ground, copper point, and chip out the stitching in both directions.

  This will leave you with a very sharp edge.

[sailordad]

i work alot of obsidion slabs
i have only been doing this for 9 months now so i wouldnt know how to go about explaing how i do it
all i can say is cut the slabs to near the size of the point/blade that ya want to make and that will save more than waste more
grind that edge,when you stop and look at the edge grind it again.i have found that you almost cant over grind obsidion
do not touch the edge as cowboy said once ya grind it.if you do touch it then regrind it
some of these guys use such fancy terms like stitching the edge and short flake run.
now i dont know what that all means(probably casue i am self taught) so maybe ya dont want to listen to me
but i probably do use these techniques and dont know it
other than that all i can say is
practice and alot of rock is the best things to do after all this is a hobby of tonnage
atleast thats what everyone told me when i started

[mullet]

  Well, didn't know I was fancy, Tim  . All I was getting at was, when you make your first run of flakes, don't try to push them all the way to the middle or across. A lot of people try this and end up pushing so hard so they can take that, one, flat spot out, they end up snapping the point. (snapping, not fancy ).  when you are knapping slabs you have to constantly; grind the edge, side to side, taking off the underhinge. Then grind your edge again, to set up your platforms, file your copper pressure flaker after each run of flakes.   IF YOU HAVE TO PUSH HARD, FILE YOUR PRESSURE FLAKER AND GRIND YOUR EDGE, AND SET UP PLATFORMS.

  It's not just pop, pop, turn it over and repeat. Thinning a Slab is just as time consuming, and to me, a lot more abrading, than working spalls. just look at some pictures of FOG's. If you want pretty points you have to take your time.

[sailordad]

Mullet: when you explain it like that,yup that how i do it.
          like i said,i cant explain how i do it or the terms you guys use.
          but thats it in a nutshell

[billy]

That's one reason I don't like working slabs....it seems the flat surfaces do not dissipate shock or bending forces as well as a lenticular shaped biface, and they break more easily.  I also find them more time consuming to make because you have square edges all the way around.  But if that's all you have, then carefully remove the square edges, and push each series of flakes farther across the surface until you have the lenticular cross section.  Flat slabs DO NOT like percussion flaking, and your support must be really good, otherwise you get a lot of breakage.  You can go to town on a spall or flake, but when it comes to slabs you must be very careful with each flake removal because they break easily.  Personally I don't like slabs.

[adb]

Here's an obsidian blade.

[attachment deleted by admin]

[Bill Skinner]

If you X the edge first before running flakes, when you do start running the flakes, it will give the slab a lenticular cross section.  The flakes may not run to center the first time, they won't hinge (break off and leave a 90 degree edge) and the second flake now has a rounded surface and will run farther.  Working a slab is more time consuming than percussion but if you have some high dollar rock, it is a lot less wasteful, when you percuss, about 90 percent of your rock ends up on the ground at your feet.  Bill

[warhawk]

Boy Im impressed with the experience that this site has thanks to all of you who have given me your ideas i'll try them and see if i can show some pictures by friday.

[mullet]

 Warhawk, those points I posted today are from slabs that Keenan sent me. All three points took about an hour and a half.