Tempered

Tempered is the past participle of temper, a controlled process used to alter properties of materials. In engineering and materials science, tempering refers to heat-treatment steps that change hardness, strength, ductility, and residual stresses. The specifics vary by material, but the common goal is to achieve a desirable balance of properties for the intended use.

Tempered glass is produced by heating ordinary glass to a high temperature and then rapidly cooling it with air or oil. This creates compressive surface stresses that increase strength, impact resistance, and thermal stability compared with annealed glass. It can be formed into panels and safety components, but cannot be cut or etched after tempering and tends to break into small, dull fragments when shattered.

Tempered steel refers to steel that has undergone a tempering heat treatment after quenching. The typical sequence is hardening (austenitizing and quenching to form martensite) followed by tempering at a subcritical temperature to relieve stresses and adjust hardness. The tempering temperature controls final hardness and toughness; higher temperatures yield tougher but softer steel. Applications include tools, springs, gears, and reinforcing components.

Other uses include tempered chocolate, which involves carefully heating and cooling cocoa butter to form stable crystalline structures, yielding a glossy finish and firm snap. In everyday language, tempered can describe something moderated or balanced, as in tempered expectations or a tempered response.