The winner of the first giveaway is Lisa Marie Shillito Roberts!!!
I'll get in touch about your address.
today I had an interview with an obsidian from Pachuca in the central highlands of Mexico!
|The monster lives!|
|Pachuca on left, Glass Buttes, Oregon on right|
|Central Mexico, southern Idaho, central Oregon|
This material seems to step fracture more often than other volcanic glasses, meaning that the slightest pressure against a poorly-created flaking platform will result in a lumpy bifacial blade. I don't use copper tools for shaping stone anymore and personally like little traits that antler pressure flaking makes. Antler tines flex with pressure and allows the release of longer flakes with shallower negative flake scars along the blade edge. Antler tines let the stone bite in a bit as you're building up pressure to detach. Smaller platforms allow thinner, finer flake detachment as there is less mass to move from the onset. I chose to make longer, thin platforms high upon the working edge.
|Here's the working edge with circles showing different platforms angles, depths and widths|
All obsidians have their own personality when it comes to pressure flaking. Some sources are brittle yet easy to flake and end in blended flake scars. Others are more plastic and give raised flakes scar margins. Mixing a more plastic material with the traits of copper pressure flaking will give pronounced flake scar definition and is good when trying to display unique flaking patterns. Less plastic materials flaked with an antler tine will give smooth, blended shapes that are sleek and utilitarian.
|large flake removal to under-cut a stack on the other edge|
This stuff is a lot of fun to play with once you figure out the best angles. I crushed a ton of flake platforms on this pachuca obsidian. multiple failed attempts to fix this problem create "stacks" on the face of the blade. These features are often a signal of an incorrect combination of platform strength, removal angle and applied force during flake removal. Poor flaking quality of a stone will also make this happen a lot. Still, I create these flaws all the time and have only recently been able to make flakes that can fix the situation. A stack as a funny thing. These features on the landscape of a biface are created by repeated attempts to remove the evidence of what was initially a small mistake with improper stabs at a fix. A stack in the wrong place means that the blade you have created will not integrate uniformly into the haft and may form a point of weakness along the cutting edge.
|Stack on a point from the mid Archaic ca. 4,000 yrs|
|The stack was approached from both sides but held fast|
But you know what? There's actually an easy fix! If you create a deep platform on the opposite margin you can undercut the whole mess from the other side with an overshot flake. So it's not at all doom and gloom by any means. An assessment of the problem and preparation for a solution will fix it up in no time flat. The blade will haft (yeah made a verb out of that) and your cutting edges will be back to uniform before you know it. fixing a stack has actually become one of my favorite little things to do while making a biface.