Karkaistut

Karkaistut is a Finnish adjective form meaning tempered or hardened, used to describe materials that have undergone a treatment to increase strength, hardness, or resilience. It is the plural participle that accompanies a noun, for example karkaistut lasit (tempered glass) or karkaistut teräkset (hardened steels).

In glass, tempered glass is produced by heating the glass near its softening point and then cooling it rapidly, creating compressive surface stress that increases strength and safety. Tempered glass is more resistant to impact and, when broken, tends to shatter into small, blunt fragments rather than sharp shards. The tempering process also constrains subsequent shaping, cutting, or drilling to pre-tempered stages or to designated edges.

In steel and other metals, karkaistu teräs refers to metal that has been heat-treated to achieve a higher hardness and wear resistance. Typical methods involve heating to form austenite, quenching to produce a harder structure, and often tempering to balance hardness with toughness. Hardened steels are used in tools, springs, bearings, and cutting edges, where increased strength is essential.

The term is widely used in industrial, architectural, and consumer contexts to indicate a material that has been treated to meet specific performance criteria. While karkaistut materials offer advantages in durability and safety, tempering and subsequent processing steps must be planned, as some tempered items are difficult to machine or modify after treatment.