Temperings

Temperings is a term used in various crafts and industries to describe a process of controlled heating and cooling applied to a material to modify its properties. The specific method and purpose of tempering depend heavily on the material being treated.

In metallurgy, tempering is most commonly associated with hardening metals, particularly steel. After a metal is heated to a high temperature and then rapidly cooled (quenched) to make it very hard, it can also become very brittle. Tempering involves reheating the hardened metal to a lower temperature than its initial hardening heat, holding it there for a specific period, and then allowing it to cool. This process reduces brittleness and increases toughness, making the metal more useful for applications where it needs to withstand impact or stress. The exact temperature and time of tempering are critical and determine the final balance between hardness and toughness.

In glassmaking, tempering refers to a process of strengthening glass. This is typically achieved by heating the glass to a high temperature and then rapidly cooling its surfaces with jets of air. This creates internal stresses within the glass, with the outer surfaces being in compression and the inner core in tension. Tempered glass is significantly stronger than annealed glass and, when broken, it shatters into small, relatively harmless pieces rather than sharp shards.

The concept of tempering can also extend to other materials and processes, such as in the creation of certain types of ceramics or in food preparation, where controlled heat treatments alter texture and flavor. However, the most prominent and widely understood use of the term "tempering" relates to metal hardening and glass strengthening.