PREVENTING BROKEN POINTS
It's so discouraging. Seems like everytime you get your points anywhere near a thin stage they break. They endsnap. They fold. Reaching your goal of thinner bifaces is just within your grasp and then it's snatched away in the blink of an eye. Well, I've been there. But I can honestly say that ever since I learned the things in this article, I haven't broken a single point while billet thinning as long as I didn't rush things and I took the time to apply the techniques. That brings up an important thing to remember. There aren't any shortcuts to creating those beautiful points. Besides, you don't want to hurry. Flintknapping is fun. Relax and concentrate on really seeing what the stone needs and you'll be happier with the results.
I learned the techniques described here from my good friend Jerry Ulrich, a knapper from Battle Creek, Michigan. After watching me knap a piece down to a 4 to 1 W/T (width to thickness) biface and then break it, he told me that there was no reason to ever break a point that had gotten that far. But I needed to memorize some things and practice them until they became second nature. I did what he said and he was right! I'll list them for you and then we'll discuss how to achieve each one of them. Here they are:
PLATFORM HAS TO BE BELOW THE CENTER LINE
Every time you are going to strike a platform make sure you have done the things in the above checklist.
Platform Is Below The Center Line
First thing is to make sure that the place where your billet is going to connect is below the center line. When you hit below the centerline, a flake comes off. When your preform is thin, and you hit above the center line, it is almost certainly going to break. As the preform gets thinner, it's very important to take a little time and really look at each platform you make. You need to make sure they're right. Do what you can to make every platform as perfect as you can and you'll be rewarded with more predictable results. As you gain experience you'll find that there are times where you might spend five minutes just preparing a platform but the results are well worth it.
Click here for a detailed explanation of the center line concept.
Isolate The Platform
Isolating a platform allows your billet to connect with certainty on the exact spot you wish to hit. It allows for concentration of all the force from that blow into that one spot. When using a moose-antler billet, striking properly abraded and isolated platforms results in large, fan-shaped thinning flakes. It's a great technique--especially for beginners.
The above picture shows an isolated and abraded platform ready for the billet. I made this one a bit exaggerated so you can get the idea, but it will still work. You can see that some of the material has been removed from either side of it so that the billet will only catch the platform. Look at it! It's right out there beggin' for it. Don't you just want to hit it? Wait a minute, OK? Let's take care of a couple more things first.
Another example of a platform set up on a ridge. The platform has to be at an angle less than 90 degrees. The relative dimensions of the platform, ridge, and preformin this drawing have been exaggerated for clarity. As the preform gets thinnerthe platforms get smaller too. Everything gets more subtle as you near the final form.
We talked a little about abrading in the last section. You also saw a picture of how our platform looked after it was abraded. We'll use this section to explain why we abrade.
Abrading is the rosetta stone of flintknapping. It's the "Eureka, I found it!" So many people who had to learn flintknapping by themselves have told me that when they discovered abrading they advanced "light years." There's good reason for this. An unabraded edge is sharp. It uses up the shock from the billet before it can do any good. Without abrading you end up with a crushed edge and a myriad of step-fractures. Abrading dulls the edge so that it has the strength to hold up under the force of the billet. On top of that, because you're hitting a blunted edge, the shock wave travels cleanly on through the stone. If you pay attention to the angle at which you are holding the piece, a long, wide, thinning flake results.
Here's another trick. Abrade a little on either side of your platforms. Then if somehow you do miss the place you intended to hit, at least you'll still remove a flake rather than damaging the edge.
Provide Support And Dampen Vibration
We're in the home stretch now. The thinner your point gets, the more important these last two rules become. Here's how you hold a preform so as to provide support and dampen vibration when you hit your platforms.
The top picture above shows how the bottom face of the preform is supported by the fingers. Only the finger that the knapper may be using to apply force for "pulling" a flake is actually applying any kind of real pressure. Mainly the fingers are there to support the whole point so that it holds up to the force of the strike. They also assist in dampening vibration. By the way, don't let your thumb clamp down and put force on the middle of the point. Let it rest closer to the back edge of the piece. That way it doesn't stop the shockwave halfway through and break the piece.
You will notice from the pictures that I like to use a piece of real leather chamois to protect my hand during knapping. I like how it's easier and less bulky to use than a glove and because it's so thin I believe you retain some of the "feel" that a bare handed knapper has. I can't explain this "feel". But you will know what I'm talking about when you "pull" enough flakes and feel the sensation of the shock from the releasing flake. In addition the leather supports the piece in the areas between your fingers and further helps reduce vibration. You double or triple the thickness in areas of the hand where an edge is seated. I strongly recommend protecting your hand-especially for beginners who are getting used to how knapped stone behaves.
The bottom picture shows the billet pressing hard and inward on the outside edge of the biface. What this does is firmly seat the "back" edge against the hand. Dampening the opposite edge to the one you are hitting does something to the shockwave as it travels through the stone that helps prevent the point from breaking. On Craig Ratzats video "Caught Knapping" he uses this technique to prevent "endsnap" when hitting the base of a point he was working on. He pressed the end opposite the one he was going to hit against his leg. If you are just holding the point out there without dampening the edge the shockwave does a mean trick and folds the piece or, if you are hitting the base or the tip, it does the "endsnap torture" trick.
After you have seated the back edge it's time to hit your platform. Now before you hit your next platform go through the above list again and then..smack it!
Above: The result of the strike using the techniques described here. The flake was 3 1/2 inches long and traveled all the way across the face to the other side.
Well, there you have it. I think you are going to be very happy with the results if you take these techniques to heart. Using these rules my bifaces went from W/T ratios averaging around 3.5 to 1, to being nicely thinned pieces in the 6/1 range in the course of two weeks-and they're getting thinner. Let me know if this helped you and Happy Chipping!
This page was last updated on 07 March 2012.
Copyright © 1999 & 2012 by Wyatt R. Knapp