Whitewash
Whitewash, or calcimine, kalsomine, calsomine, or lime paint is a low-cost type of paint made from slaked lime (calcium hydroxide, Ca(OH)2) and chalk (calcium carbonate, (CaCO3), sometimes known as "whiting". Various other additives are also used.
Whitewash cures through a reaction with carbon dioxide in the atmosphere to form calcium carbonate in the form of calcite, a reaction known as carbonation.
It is usually applied to exteriors; however, it is traditionally used for interiors in food preparation areas, particularly rural dairies, for its mildly antibacterial properties. Occasionally, it is coloured and used on structures such as the hallways of apartment buildings, but it is not popular for this as it can rub off onto clothing to a small degree. In Britain and Ireland, whitewash was used historically, for both interiors and exteriors, in 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".
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. Damping down is not difficult but it does need to be considered before application of the limewash.
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