MANUFACTURING CONSIDERATIONS
1. General. The production of lithic tools begins with the selection of the raw
material (rock) for the type tool required. If reduction by percussion flaking
is planned, the rock must be knappable, i.e. flakes with a conchoidal fracture.
After determining knappability, the knapper must decide if altering is required.
Altering, primarily by heating the rock, is the normal method and heating to a
specific temperature makes the rock easier to shape into the desired tool. Some
rocks may be soaked in water and their knappability increases significantly.
A skilled knapper, using hammer stones for the initial shaping, can produce a
workable tool from any rock he has available without alteration. After the tool
has achieved the desired thinness and shape, the final work is accomplished by
pressure flaking using a deer antler tine.
2. Material Selection. In west central Louisiana the naturally occurring
materials available for tool production are limited to silicified wood,
(primarily palm wood), "petrified wood", opalized sandstone, and chert cobbles.
High grade palm wood has never been plentiful, but, when available, resulted in
the production of exceptionally well made tools. The petrified wood in this area
is normally of a poor grade and tools are of poor quality. The opalized
sandstone is very difficult to knapp, however some excellent tools were
produced. The chert, exposed when creeks cut through the veins, was the material
most often used by the local knapper. The cobbles varied in size, some cobbles
can weigh up to 10 pounds, but normally weigh less than 1 pound. The variety of
sizes and shapes available benefit the knapper by reducing the effort required
in tool production if he searches for the appropriate cobble. Often the knapper
can locate a cobble with a white cortex and light tan center that can be easily
knapped without any alteration. However, the majority of the time the chert has
to be heat treated.
3. Heat Treatment. Cobbles are selected, tested for knappability by knocking
off a small flake, then further shaped by removing all the cortex. Depending on
how "tough" the cobble is, it should be reduced in size. Care must be taken to
not remove so much material the cobble is too small to be of any value. Any
hinge/step fracturing is an indicator to stop the reduction procedure until
altered. Attempt to get the cobbles all the same thickness if possible. Heat
treating is a controlled procedure and can not be accelerated without penalty.
The following is a procedure similar to that used by the early knappers in tool
production.
a. Weather. Select a day with a temperature minimum of 60ø Fahrenheit, a
forecast without cool fronts or rain for at least 3 days, and preferably no
breezes.
b. Site. A cleared spot free from possible threat of the fire getting out
of control. A sandy soil is preferred. Access to all sides of the fire pit is
desired. An ample supply of wood for 10 hours continuous burning is required.
c. Pit Preparation. Dig a pit 12" deep and large enough to hold all the
cobbles when placed side to side, not layered. Do not scatter the fill removed
from the pit, it will be used when the heating is complete. Pile the dirt near
the sides to allow the heat from the fire to dry and warm the dirt. If the pit
bottom is moist, build a fire in the pit to dry the pit out. After the drying
fire has burned down, cover the ashes with two inches of dry sand. Place the
cobbles on the sand, ensuring they do not touch( 1/2 inch separation). Cover the
cobbles with 2 - 3 inches of sand. The exact covering depth will depend on the
type of chert you have available in your area. Trial and error will determine
the best covering depth of sand.
d. Firing. Gently place the wood over the pit, never throw any wood
the pit as this will expose the chert. Ignite the fire and keep a roaring
going for 10 hours. Allow the fire to die down to hot ashes. Gently cover
ashes with the fill previously removed from the pit. I have found a more
effective procedure is to cover the pit with tin, then cover the tin with
material removed from the pit.
into
fire
the
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e. Cooling Down. Wait 24 hours before attempting to remove a cobble. If it
is too hot to hold in the exposed palm, wait another 24 hours. Some will have
fractured, but most will be properly altered. If more than 10% are fractured,
you will have to increase the sand covering over the cobbles for the next time
you alter this type chert.. If none are fractured, you may have to reduce the
sand covering. Knapping the cobbles will assist in determining heat adjustments.
4. Knapping. The two forms of flake removal are direct percussion and indirect percussion. The target stone can be placed on the knee,
held down with the hand, or held in the hand away from the knee. The knapper
usually sits on a chair, but may kneel on one knee. The billet, usually a deer
horn type, is used to drive flakes from the target stone. Billets may be stones
called hammer stones. The major advantage is the hammer stone, used to initially
shape a cobble, may also be used to knapp the toughest of chert, producing a
finished tool, without alteration. A dart point, the Calcasieu point, common to
west central Louisiana, was probably produced without alteration using the
hammer stone as the primary billet.
5. Finishing. The pressure flaking technique is used to dress the sides of the
tool and notch the base. A sharpened deer tine is used. By applying inward
pressure and a sharp downward thrust, small finishing flakes are removed from
the edges and the notches. The notches are then ground to remove sharp edges
which would cut the rawhide used to secure the point to a shaft.
6. Another inexpensive method of altering is to use an oven (not the oven in
your house) such as a turkey oven. For small test lots use an old crock pot or
deep fat fryer. For local chert in the Vernon Parish area, most will only
require a temperature between 300 F to 450 F. Place one inch of sand in the
turkey oven and cobbles/preforms on the sand. Since the oven allows control of
the temperature, place three layers of cobbles/preforms in the oven. Then place
an oven thermometer on the top of the material and cover the top with three
inches of fiberglass insulation before closing the cover. The temperature is
increased about 50 F each hour until 400 F is reached. The oven thermometer is
checked for the inside temperature, never taking more than 10 seconds for the
check. The oven is held at 400 F for about two hours, then the cool down begins,
about 50 F per hour. In hot weather you may be able to unplug the oven and let
it cool down for at least 24 hours without damage to the material.
Briggs
4/97
pg 2 of 2