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reduction in the linear dimensions and volume of materials caused by loss of moisture, contraction, hardening, and other processes. The shrinkage of ceramics and concrete is of considerable importance. Molded clay products are subject to shrinkage during drying and firing. The shrinkage of concrete occurs during air hardening and is due to the evaporation of water from the capillaries in cement rock. The shrinkage of metals and metal alloys during crystallization is due to the reduction in volume on transition from the liquid state to the solid, the additional reduction in volume on cooling from the solidification point to room temperature, and the penetration of molten metal into the inner part of the congealing mass and all the cavities and cracks formed during molding of the ingot or shaped casting.
Reduction over time in the vertical dimensions of structural components, such as stone and wood walls and heat-insulating fill, is often called settling.