Kapillärtäckning

Kapillärtäckning is a Swedish term describing the spreading or coverage of a liquid through porous materials driven by capillary forces. In practice, it refers to how liquids are drawn into and along small pores, often leading to moisture appearing at surfaces or within layers where liquid would not reach by gravity alone.

The mechanism relies on capillary pressure, which arises from surface tension and the contact angle between liquid and solid. Smaller pores create higher capillary rise, and the rise is balanced by gravity and evaporation, resulting in a characteristic capillary fringe beneath the liquid source. The extent of kapillärtäckning depends on pore size distribution, porosity, liquid properties (surface tension, viscosity), and the structure of the material.

In soils and geology, kapillärtäckning explains how groundwater moisture can move upward into the root zone, affecting plant available water and soil moisture regimes. In building physics, capillary action can transport moisture from the ground through masonry and into interior walls, contributing to rising damp if not controlled. Materials and design choices to mitigate this include capillary barriers or kapillärbrytare, damp-proof membranes, and ventilated cavities that limit upward wicking.

In textiles, kapillärtäckning underlies wicking behavior, where fabrics draw moisture away from the body to the exterior. Coatings and Papers also exploit capillary spreading to promote uniform wetting or controlled absorption.

Measurement and modeling of kapillärtäckning employ capillary rise tests and models such as the Washburn equation for simple capillaries, as well as continuum approaches for complex porous media. Understanding capillärtäckning helps in moisture management, material selection, and damp-proofing across disciplines.