Современная архитектура и строительство. Рябцева Е.В - 38 стр.

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the material to which they are applied (wood, steel, mineral backings, etc.). The most logical and universal clas-
sification, however, is according to the binding agent used; e.g. alkyd resin; or silicate paints based on the use
of potassium silicate. The painting system and the background material have a reciprocal influence on each
other and determine the properties of the finished construction in terms of impermeability, vapour diffusion and
strength.
Paint, as a liquid surface coating, consists of binders, solvents, fillers, pigments and additives, which to-
gether determine the properties of a product and its coloration. Up to the middle of the 20th century, paints
were mixed by the trade people who used them. Today, most paints come as finished products ready mixed by
the manufacturers. This ensures constant, controllable quality standards, but the subtle variations in tone and the
liveliness of traditionally mixed paints have disappeared. Binders belong to the non-volatile components of
paint and are important for the adhesion of the material on various backgrounds. Solvents serve to dissolve the
binders and make them workable. Pigments determine the colour and may be of inorganic, mineral or organic
origin. Additives can also be incorporated to improve the storage life, workability, visual quality, etc.
The first paints used by man were made of earth. The cave dwellers of Lascaux used red ochre or black
manganese earth, with added charcoal and red chalk, more than 15,000 years before Christ. Later, lime milk
was employed for whitewashing plaster or stone. Over the millennia, paints underwent a constant process of
improvement in respect of their adhesion and brushability through the addition of natural substances like curd
and linseed oil. For lime-based paints, slaked white lime diluted with water Ca(OH)
2
is used as a binder. Since
lime-based paints require constant maintenance, however, their use externally is restricted mainly to historical
buildings where it is necessary to match new with existing materials. In external situations, there is also a dan-
ger that the lime content will be converted into gypsum as a result of acid rain. Internally, on the other hand,
lime-based paints are used today for their good vapour-diffusing and absorbent properties and their ability to
regulate moisture levels. In addition, they are greatly appreciated for the tonal radiance they help to achieve.
Distempers and casein paints, which are mainly suitable for internal use, no longer play an important role
nowadays, except in biologically correct forms of construction.
Today, the wide range of paint products on the market has made it necessary to establish certain criteria for
the selection of the appropriate type for a specific situation. A new system of classification for facade paints is
at present being drawn up and is scheduled to be completed next year. This is based on the so-called S-value
(the depth of an air-layer with the equivalent rate of diffusion) and the W-value (the degree of water repel-
lence), which form the measure of comparison. This new code of classification will allow the selection of paints
that are precisely matched to a particular backing.
In order to determine the moisture balance of a component, a distinction must be made between paints that
form a film on drying and those that do not. In conjunction with the binding agent used, additives can be
incorporated in dispersion substances to control the formation of a surface film and thus to regulate the
permeability or moisture resistance of the coating, if no film is formed, water glass can penetrate mineral paints
and cause a reaction in the bearing layer (silification). These processes have a great influence on the industrial
manufacture of paints today and result in a division of products into dispersion paints on the one hand, and
silicate or mineral-based paints on the other.
Potassium silicate is a syrupy fluid created through the fusion of quartz with potash or soda. It is used as a
fixative or binder for silicate paints. Their development dates back to the late 19th century. Pure silicate paints
are two-component products consisting of a fixative and coloured powder (mineral pigments with fillers). The
materials have to be soaked or mixed a day before use. When the paint dries, the water glass does not form a
sealed film; instead, a process of petrification or silification occurs in the mineral base. The open-pore structure
ensures a high degree of permeability to vapour and allows a rapid drying process. The surface finish is also
highly resistant to pollutants and aggressive substances. That is why silicate paints are frequently used in place
of historical lime-based paints in conservation. In such situations, the strength of the rendering should be co-
ordinated with the surface finish. Because the mineral binding agent has the same coefficient of expansion as
the mineral base, stresses caused by changes of temperature - and the resulting cracking - can be avoided. Since
their development at the beginning of the 20th century, water-based (dispersion) paints have come to play a ma-
jor role in view of their simple preparation and broad range of application. The binding agent consists of po-
lymerisation resins dispersed in water, to which softeners, fillers and pigments are added as required. In chemi-
cal terms, mixes in which the substances are not dissolved but merely finely distributed in the solvent are
known as "dispersions". Where the finely distributed matter is a solid, one speaks of a "suspension"; where it is
a fluid, it is referred to as an "emulsion". These paints are suited to both internal and external use. The way they
set depends on the nature of the suspension or emulsion substance they contain as well as on the drying-out
process. At all events, a continuous film is formed. As an organic system, the paint does not bond with the min-

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