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Paint

- paint decoration has a long history stretching from cave dwelling to the present. Materials have varied over the centuries, but in more recent times, there have been three main products, water based paints or distempers, oil based paints and varnishes. To colour usually refers to use of distemper, to paint, can usually be taken to mean the use of an oil based product.

Several recipes exist for distempers or whitewash, all of which basically involve a white base pigment which is often crushed chalk, a size and water. When used as a paint, the water evaporated leaving the chalk bound onto the surface. Distempers were cheap, but had no resistance to weather. Oil paints which could be used both inside and outside, required a base pigment usually white lead, to be mixed in an oil, usually linseed oil. Rather than evaporation occuring, the mix hardened to form a protective coat. Varnish was produced by dissolving a natural resin in a solvent, alcohol, linseed oil and oil of turpentine were all commonly used.

Pigments had to be added to both water and oil based paints which were usually white. Pigments not only gave colour but in some cases enhanced the protective properties of the paint. In the past choice of colour was limited by the cost and availability of pigments. When one colour meets another it is said to be 'cut in'. White lead is obtained by forming sheets of lead into coils which are then placed in clay pots with some vinegar at the bottom (lead and vinegar are kept apart). When subject to gentle heat, (it was common to stand the pots in horse dung) the vapour of the vinegar corrodes the lead. The white flakes which come off, are ground down and saturated with linseed oil to form white lead. Lead paint is poisonous but is also very good on wood, because it is breathable, and under certain circumstances, it is possible to obtain a relaxation of the building regulations to use it on historic buildings

Paint scraping is the process of carefully separating samples of paint from a wall for the purpose of establishing original colour schemes. This is a very scientific process which also depends to a great deal on experience and knowledge of paint history and decoration. For example, one layer of paint overlaid by another can result in a chemical reaction which distorts colour, and more obviously, most colours and types of paint fade differentially under certain light conditions.

"Curtaining" is the term used to describe a coat of paint which has been applied too thickly and has sagged into curved ridges, while "crocodiling" is used to describe paint which has cracked usually as a result of heat.