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Bifacial reduction flake, good for making an arrow point. 2 3/4" long.
SELECT A FLAKE:
After percussion flaking on a large biface, you will have a variety
of shapes and sizes of trash flakes (called "debitage"). Look through the
debitage and save anything you think you can practice on. Choose thin flakes
(around 1/4 inch or slightly thicker) that are reasonably straight and
as close as possible to having uniform thickness all over. The edges should
be thin, and the center and the striking platform areas should be the thickest
portions of the flake. The flake shown above has one ridge running down
the dorsal side. A lot of flakes have two or sometimes three ridges running
approximately parallel to each other. The dorsal side is more difficult
to work because of the concave surfaces between the ridges, the ventral
side is easier to work because it is smooth and convex. Try to find good
quality flakes by looking at the finish. Keep in mind that after you heat
treat the flake and begin to pressure flake it, it will usually be
glossier and easier to work. Avoid flakes that have crystal pockets or
quartzite in or near the center, it will greatly interfere when you are
thinning the preform. Also avoid flakes that have cortex on them as these
are a chore to work with.
CREATING PLATFORMS:
A platform is a knapper’s term for an artificially shaped beveled
edge used to drive long flakes off from the opposite side. Without a platform,
the edge can mislead you as to where you should apply pressure. Platforms
also strengthen the edge and prevent the flake you are removing from shattering
and causing a hinge or step fracture. Creating good platforms and GRINDING
THEM DULL are key factors in successfully removing large flakes. You will
need a flat surface to work on, like a sturdy table, or you can sit on
the ground and use a brick.
Place a rubber pad on the flat surface and put the heat treated
flake on the pad, dorsal side up (the side with the ridges). If you are
right-handed, hold the flake down with your left hand, and hold the pressure
flaker firmly with your right hand. Place the tip of the pressure flaker
on the flint near the edge and press down hard until you remove a short
flake. Move the tip of the flaker over and repeat until you have beveled
it all around. This can also be done faster by percussion with a small
billet.
Turn the flake over so the ventral side (the smooth side) is facing up, and repeat the process all the way around on the other side. Try to make your edges smooth all the way around.
Your piece should now look like the preform below. Now, dull the edges all the way around with the grindstone. You have now created the platforms for the first thinning flakes. Notice how the edge is towards the flat side. The edge of a platform should be below the center line, or towards the side to be thinned. The flatter side should be thinned first.
THE FIRST STAGE OF THINNING:
After dulling the platform, you are ready to remove the first thinning flakes. Start with the ventral or smooth side facing the notched pad. Your goal is to remove flakes as long as possible, up and down both edges on the ventral side. You can use your pressure flaker, but it is easier on your wrist, and you will probably have better results if you use the Ishi stick. If you are right-handed, hold the tip end of the Ishi stick with your right hand with the other end under your right arm, between your elbow and the side of your belly. Place the notched pad in the palm of your left hand, with the groove aimed towards your wrist. Put the preform on the pad, flat side down, and hold it with your fingers. Bend the wrist holding the preform back while gripping the preform against the pad. Place the tip of the Ishi stick onto the edge of the preform where you will be removing the flake from. Use the strength of your legs to press hard on the edge, and while you are pressing hard, flick the wrist that holds the Ishi stick towards the pad. Pressing into or towards the center of the preform (see arrows) will give you enough energy to drive off long flakes; and flicking your wrist actually initiates the break.
Using the Ishi stick requires some practice to do successfully, and
it would be a good idea to go to knap-ins and have people show you, or
you can practice by watching a flintknapping video and trying to imitate
what the instructor is doing. It probably won’t work correctly the first
few times, but you can learn from your mistakes.
If you are having problems with the flakes breaking short causing
step fractures, click on dealing with hinge fractures,
and preventing hinge fractures.
Most of the time I like to work the flat side of the preform first,
for two reasons: if you work the flat side first, you will make the preform
narrower and you will have less distance to go when working the tougher
convex side. The other reason is the flat side is simply easier to work
because it is smoother – especially on flakes like this example. It saves
labor on both sides. Once you have completed the ventral or flat side along
both edges, put the pad on the table with the preform on it, with the side
you just worked down. Create platforms by pressing down near the edges
with the pressure flaker. As before, this may be faster by holding the
preform in your hand and using the small billet.
After the platform is created along both edges, make sure it is even and straight, and then dull it with the grindstone. Turn the preform over and use the Ishi stick to thin the dorsal side in the same way you did the ventral or flat side. Try to remove as long of flakes as you can, and try to eliminate concave edges in the cross section. This may require removing shorter flakes to make it more convex (see right side of illustration below). Where it is possible, try to remove the dorsal ridge in the center (see left side). This may take several passes with the Ishi stick, but don’t forget to create and dull platforms, and thin the opposite side in between passes.
Your preform should now look similar to the preform below.
THE SECOND STAGE OF THINNING:
You may need to create platforms, but in this example there is a natural platform and it just needs to be made neat and dulled with the grindstone. Use the Ishi stick to remove thinning flakes. Again, it is better to do the flat side first. Try to make these flakes reach at least to the center – past the center is better.
Once you have thinned both edges of the flattest side, create platforms for removing flakes from the opposite side. Don’t forget to dull them.
Look over the preform and find areas that are thick and look like you can remove flakes to thin it in these areas. Keep in mind that the midsection should be the thickest portion of the preform. Create platforms in the appropriate places and dull them.
FINAL THINNING:
Turn the piece over and press towards the center with the Ishi stick to remove thinning flakes. Again, these should reach at least to the center.
Flip the piece over and use your Ishi stick or pressure flaker to
remove the final thinning flakes.
Examples:
THE FINISHED PREFORM:
Your preform should look similar to this one. If it does, you are
doing well. This one isn’t real thin, but if you haven’t been knapping
for long and can make one as thin as this, you are well on your way. This
particular preform is ideal for making a Perdiz
arrow point. To continue, see the page on notching.
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