Here's
the rock after Doc has carefully removed almost all of the outer layers
(the cortex). Note a little of it still remaining at the right hand
end. The cortex is highly weathered and doesn't have that characteristically
shiny obsidian surface. The rock is becoming more and more convex
in cross section, which is Doc's ultimate aim. Flakes will travel
very well over a convex surface, and convex blades have the best characteristics
of both strength and sharp edge for durability.
As
the edges become thinner and sharper, Doc is paying particular attention
to thickening the incredibly sharp edge by abrading it away with a coarse
stone. Modern knappers use pieces of grindstone, where prehistoric knappers
would have used coarse sandstone. Thickening the edge allows the force
of each blow to transfer efficiently into the stone, resulting in a
clean break, in the desired place, rather than allowing the sharp but
weaker edge to crush. Crushing either fails to detach a flake, or only
allows the break to travel part way into the stone, then break off leaving
an ugly ledge which will be very difficult to deal with later (a common
beginner's mistake). A not to be overlooked advantage to abrading the
edge is the stone is much safer to handle. Freshly flaked edges are
so sharp you can easily cut yourself and not even notice until the area
around you begins to fill with red fluid!
Here's
the rock several series of flakes later, at a stage called a "biface."
This is the stage at which Native Americans would have used to transport
the stone for trading or taking home. Rather than carrying a lot of
waste stone (remember, no pickup trucks back then), Native Americans
would have reduced the raw stone to this stage, and carried them away
in baskets. From this stage, a large knife blade or spear point could
be produced at will, and most of the subsequent waste flakes taken off
would be recycled as small cutting tools or arrow points.
Here
it is from a side view. At this stage, the rock is at least half the
weight of the original.All
contents copyrighted © 2002 | Tom Sterling
Tom Sterling PO Box 1621 Coupeville WA 98239
Last Updated:Monday March 24, 2008
All
contents copyrighted © 2002 | Tom Sterling
Tom Sterling PO Box 1621 Coupeville WA 98239
Last Updated:Monday March 24, 2008