Whitewash

Whitewash, or calcimine, kalsomine, calsomine, or lime paint is a type of paint made from slaked lime (calcium hydroxide, Ca(OH)2) or chalk calcium carbonate, (CaCO3), sometimes known as "whiting". Various other additives are sometimes used. Whitewash cures through a reaction with carbon dioxide in the atmosphere to form calcium carbonate in the form of calcite, a type of reaction generally known as carbonation or by the more specific term, carbonatation. It is usually applied to exteriors, or interiors of rural dairies because of its mildly antibacterial properties. Whitewash can be tinted for decorative use and is sometimes painted inside structures such as the hallways of apartment buildings. A small amount can rub off onto clothing. In Britain and Ireland, whitewash was used historically in interiors and exteriors of workers' cottages and still retains something of this association with rural poverty. In the United States, a similar attitude is expressed in the old saying "Too proud to whitewash and too poor to paint." The historic California Missions were commonly whitewashed, giving them their distinctive bright white appearance. Whitewash is especially compatible with masonry because it is absorbed easily and the resultant chemical reaction hardens the medium. Lime wash is pure slaked lime in water. It produces a unique surface glow due to the double refraction of calcite crystals. Limewash and whitewash both cure to become the same material. When whitewash or limewash is initially applied, it has very low opacity, which can lead novices to overthicken the paint. Drying increases opacity and subsequent curing increases opacity even further. Limewash relies on being drawn into a substrate unlike a modern paint that adheres to the surface. The process of being drawn in needs to be controlled by damping down. If a wall is not damped, it can leave the lime and pigments on the surface powdery; if the wall is saturated, then there is no surface tension and this can result in failure of the limewash.