How Tufa Stone was used in Casting 

Tufa Stone as a Mold

Tufa stone is a form of sandstone.  Tufa stone is created from crushed volcanic ash which is relatively soft and easier to work with than sandstone when making the carvings.

The Tufa Stone is cut to the desired size and shape which often resembles a brick.  Usually, a design is carved into just one of the interior sides of the Tufa Stone.  Sand casting evolved from casting using sandstone or Tufa stone, a relatively soft stone created from compacted volcanic ash.  Sandstone held up better but the Tufa was easier to carve.  Carving the original design into the Tufa stone can take as much as 16 hours, depending upon the complexity of the design.

After carving a mold and prior to pouring molten Sterling silver into it, the carver blackens the inside of the mold by using an acetylene torch.  He lights his torch with only the acetylene flow turned on and, in the absence of oxygen to burn off the carbon, the inside of the mold is blackened.  After each piece is made, the Tufa stone mold is destroyed because it is believed the spirit of the artist has been transferred from the stone into the jewelry.

This work was all done by artists who where trained by Shamans to be the best carvers and artists in Central America.  They where know as Indigo artists.  This was because they had a purplish tint to their skin from working around the carbide that was used to creat the Aceylene.  It was said that they used to breath it in and then expel it into a fire.  If they had the mixture right it would cause an explosion.  The problem they had was that the carvers sometimes got a little to much air mixed in and the explosion would take place in thier mouth instead of in the fire.

They lost a lot of good artists this way.  Sometimes it blew they back of thier heads right off.  They where called Hot Heads.  The shamans finally banned the artists from chewing Cocoa leaves and that cooled them down.