Kilnformed  glass  
Glass was fired in special kilns 
at 800°C as early as 
year 2000 BC.
 
This technique is called glass fusing.
The Egyptians and Romans 
were the most advanced, and wonderful collections can be 
seen in museums e.g. Corning, New York.
http://www.cmog.org

From 500 A.D to the early 1900´s one can hardly see any fused glass objects.
During the Renaissance in Europe glass technology went through its greatest growth, and greater blowing knowledge was desired.

Glass fusing was nearly forgotten, and it was rediscovered in USA 
as late as in the 1940´s.

There are now many glass artists 
all over the world working with glassfusing.