Lot (6) large vintage Czech brown sintered glass beads

Lot (6) Vintage Czech volcanic look brown sintered glass beads. Each bead will always be different and they have large holes making them ideal for cord or leather stringing. These beads are extremely labor intensive to make and are no longer produced. 

Origin: Czech circa 1970's
Size: 15 - 17 mm 9/16" - 11/16" approx. These are very variable in size and texture
Material: Glass. 
Condition: Authentic vintage condition. 
Quantity: 6
 
Technology: Sintering is the process of forming a solid mass of material by heat and/or pressure without melting it to the point of liquification. The main component of sinter is crushed feldspar glass which, combined with other materials and fired in a mold at high temperatures produces a product that can not be achieved in glass by any other method. Coral effect beads are fired with wood in which burns away to produce the irregular bubble effect in the glass.
 
History: In the Jizera Mountains the company Gebrüder Redlhammer was the first to launch the industrial production of “glass-porcelain” beads and buttons. In the second half of the 20th century this production line was taken up by Preciosa, which also made sintered mosaic stones used on façades. At the end of the 1980's, Preciosa decided to stop producing sinter due to the rising cost.