Underlayers

Underlayers are layers situated beneath a primary surface layer, serving to improve adhesion, durability, appearance, or function. They are common across fields such as art, coatings, textiles, and geology, where a base layer provides a stable foundation for subsequent materials.

In art and painting, underlayers include grounds such as gesso or size applied to the support before painting. They improve adhesion, regulate moisture transfer, influence the tonal range, and help prevent discoloration from the surface. Underpainting, a tonal underlayer, guides subsequent color work and can support glazing techniques.

In coatings and construction, underlayers or primers are applied beneath top coats to enhance adhesion, block stains, prevent corrosion, and provide a uniform base. They may be acrylic, epoxy, or zinc-rich primers on metal, wood primers, or plaster bases in walls. The choice of underlayer depends on the substrate and the desired durability and appearance.

In textiles and fashion, underlayers refer to garments worn beneath the outer clothing, such as underwear, thermal tops, or moisture-wicking base layers. They regulate warmth and moisture, add opacity, and can influence the overall fit and comfort of an ensemble.

In geology and soil science, underlayers describe subjacent layers such as bedrock or parent materials beneath soils or sediments. These underlayers affect drainage, stability, nutrient availability, and engineering considerations in construction and land use.

Overall, the term underlayer is context-dependent, with materials and purposes varying by discipline.