Obsidian

Obsidian

Volcano glass is formed by lava which cools quickly.  It contains a lot of silica.  I find that I enjoy trying to show it in the most informative light.  I am using flash instead of incandescent lights.  It is not as easy to set up the lights with flash.  I must anticipate what the light will do.  Digital makes this easier because I can look at the camera's LED monitor and learn what the light did immediately rather than wait for the film to be processed.  

Obsidian fractures to sharp edges.  It, among other materials, is still used on surgical scalpel blades.  Obsidian is metastable on the Earth's surface.  It breaks down in the presence of water.  None has been found older than 150 million years because of this.  It breaks down to Perlite, which is used as a soil amendment because of its lack of density.

Obsidian

This piece is thin, having two sides.  I found it interesting to try to show the surface features with the light.  I had to use FEC, flash exposure compensation, of -2 because my camera meter and yours tries to make everything gray.  I had to do this to get it black.  The features on the second side required me to put another light near the camera.

setup

The "master flash" is off.  It only functions to control the others.  I had to move the one near to camera to get the right angle.

setup closeup

I used a Stofen diffuser on that flash.  I placed the gray mat behind it so that you could see it in this shot.  It was not there when I captured the image of the Obsidian.

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