Under this heading must be included whitewash, distemper, oil-bound or washable distemper or water paint, and plastic or texture paints, all of which are considered in greater detail elsewhere in this work. In addition, there are a few other preparations of some interest to the decorator which, since water plays an important part in their composition, may well be summarised here. They include:
These preparations, otherwise known as Water-glass Paints, are made by grinding pigments in a solution of silicate of soda (water-glass). This translucent, syrupy fluid holds the particles well in suspension but owing to its strongly alkaline nature, only those pigments which are unaffected by alkali can be used, so that the range is somewhat restricted. These paints are relatively cheap and have good fire-resisting properties, and are consequently often employed for such purposes as painting theatrical scenery: on exposure, however, the coating is liable to develop efflorescence and also to attack any film of oil paint which may subsequently be applied directly on top of it.
These represent a relatively new development but one which should be extensively used in the near future. They consist of Portland cement, with ingredients added to regulate the setting, and are sold in powder form, to which water is added before application. They can be used on new or old cement, concrete, lime plaster, and most forms of brickwork, but not on old paint or distemper work or on wood or metal. They are unaffected by alkali, are moisture-resisting and can be applied to a damp surface, and are more reliable and effective than cement washes made up by the painter himself.
Although the possibilities of using a lanoline or wool-grease emulsion as a binder for paints have been realised for some considerable time, it was not until the last war that coatings made on this basis were used on any considerable scale. They are available in a wide range of colourings, have good moisture-resisting properties and excellent adhesion. They are chiefly employed for exterior work, producing a film which remains soft and is easily abraded. Films of this kind must be removed before the surface is recoated with ordinary paint, as the wool-grease content will prevent an oil paint from drying and hardening.
Bituminous Water Paints
In these finishes, the vehicle is an emulsion of bitumen in water. They have good weather-resisting properties and are chiefly – though not exclusively – employed for outside work. The range of colours in which they are available is somewhat limited.