and properly built striking platforms are one major
key to predictable flake removal. Please note that
one must have an understand knapping "terminology"
to benefit from this article. Platforms have four
basic components. All four components must have
the proper characteristics for a flake to be removed
predictably, and if it does not, the struck flake
(if any) WILL become undesirable. Lets look at the
platform's components and why each part is so essential.
You must understand that these four components almost
always have to be created from scratch. Rarely are
they just sitting there waiting for your eager billet!
These are also listed in the order they should be
made. The descriptions here are intended for bi-facial
preform stages but can be applied to spalls. Note
that one must be quite proficient with a pressure
flaker before you master percussion flaking. This
is because great percussion platforms start with
good pressure flaking.
Now that we have divided the platform into four
parts, lets give them all a letter code: "A",
"B", "C" and "D",
as shown in fig. 1. I will discuss the following
topics relating to each platform component.
1. It's purpose and/or function
2. "How to make them"
3. The attributes it should have
4. Trouble shooting... cause and effect of poorly
made and or Improperly prepared platforms
The first we will look at is "A".
This is the part commonly referred to as the "bevel".
The purpose of the "bevel" is that it
serves as the surface that is actually struck to
produce the flake. How do we go about making the
bevel? The most accurate way is to use a SHARP pressure
flaker. You can use a billet to produce this on
an early stage perform or spall. It is highly recommended
that you use a pressure flaker to make this part.
What attributes should part "A" have?
This part should have a bevel some where near 45
degrees. This angle can be changed by making another
"pass" or modifying angle of pressure.
The bevel should be smooth. What I mean by this
is that it should not contain irregular bumps, humps
and micro ridges. It should be just as if you used
a router on a piece of wood.
Part "B" gives support to the strike.
It is actually made from part "A". There
are many ways to make this. The basic idea is that
you're actually removing extremely tiny chips off
the bottom or underside of the "bevel".
(This is the same side the thinning flake will be
removed from.) Remember, your not really abrading
the edge so much as shaping it. Here's a couple
ways of doing this. The first way is to use a course
abrader. Just rake the edge downward gently and
repeating this process just long enough to feel
less resistance as the abrader is raked downward.
You can also rake off these "micro" flakes
with the edge of your pressure flaker or use a copper
bar to do the same thing. Keep in mind this is a
very important step! If you rake it too hard or
use or use excessive force it will be too strong
and will greatly stress the stone upon striking
it. Rake thick performs harder than thin ones. If
"B" is not raked enough it will cause
the platform to crush or cause a step fracture very
close to the edge. Too much and you will break it!
So don't over do it.
Moving onto part "C". This part is
also made from "A". It is the polished
area that your billet actually strikes. It is better
described as polished but commonly referred to as
abraded. Polishing sounds so much more precise and
civilized. To prepare this part properly one must
first have created "A" and "B"
flawlessly! You simply grind up and down the platform
edge. What I mean by this is your grinding from
base to tip. Another description of this is if you're
holding the preform flat, the grinding motion is
horizontal NOT vertical. A vertical motion will
destroy the platform. You want to use course abraders
for preforms thicker than 5 to 1 width to thickness
and a medium abrader for thinner bi-faces. Be cautious
not to over grind, this will also cause splits or
breakage. Keep in mind... the better you make your
platforms... the less grinding they will need!
Finally part "D". This is what I like
to refer to as the "road" the flake will
travel down. This must be closely looked at before
you decide to remove any material for the purpose
of platform construction. If the surface area of
part "D" is irregular, then it must be
corrected before an attempt at flake removal is
made. Simply put, don't waist the time and circumference
of your bi-face trying to chip off an area with
a stack or concavity. Just work on either side of
it. Build platforms to target areas with good convexities.
Stay away from concavities. You can modify the surface
of your bi-face by pressure flaking if necessary.
You must be careful not to cause "micro"
steps with your billet or Ishi stick. It will just
be more trash for your thinning flake to contend
Just remember to take your time and analyze. Be
safe and have fun!
- Mark Bracken-