Hiillostus

Hiillostus is a Finnish craft term describing several heat-based surface-treatment techniques applied to different materials. The core idea is to use heat, sometimes in combination with carbon-rich atmospheres, to modify the surface appearance or properties of an object. In metalworking, hiillostus refers to processes where targeted heating and cooling produce patinas, color changes, or texturing. Techniques may involve direct flame exposure, furnace annealing, or post-heating patination and can yield a darkened, uneven, or patterned finish that highlights grain or pattern. In ceramics, hiillostus can denote a firing style that influences glaze behavior or body surface, often yielding dense, satin, or smoky surfaces depending on atmosphere and temperature. In wood and other organic materials, the term can describe heat-treatment methods that alter color and durability, sometimes through torrefaction-like processes that decompose resin and lignin to a darker finish. The term is regional and craft-context dependent; it often appears in cataloging of traditional Finnish crafts, museum labels, and artist statements to signal a connection to historical techniques. Contemporary usage may reinterpret hiillostus as a broad indicator of a handcrafted, heat-influenced surface rather than a single standardized process. See also: patination, metal patina, ceramic firing, wood heat-treatment.