Thermal Operations Annealing, Tempering, and Sintering

The tempering process entails heating a solid (generally a metal or an alloy) to a temperature Just below its melting point and then cooling it rapidly. In the past, tempering was used exclusively for hardening metals and alloys, especially steel. In more recent times, since the twentieth 

Sintering processes have been used since antiquity to alter the properties of ores and ore concentrates, powdered metals and alloys such as bloomery iron, ceramics, and glass. Bioomery iron, for example, was sintered in a forge, and the operation was often referred to as forge sintering. 

TABLE 31 Analytical Techniques Frequently Used to Study Ancient Glass  

Auger emission spectroscopy Surface Ciliberto and Spoto (2003) 

The main source of silica in antiquity, as today, was sand and, very occasionally, cmshed rock or pebbles. The most common modifier was soda, which was obtained from natron lakes, as in ancient Egypt, for example, or from vegetable ash. Most lime was derived from limestone, although some lime could also enter the mixture of glass raw materials together with soda 

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