Cement Paints are water wet-able dry powders, consisting of white Portland cement, pigments, wetting agents, and water repellents. Cement clinkers are ground with pigments, but without the customary addition of gypsum. Addition of water repellent compounds, take over the function of retarding the setting time, in absence of gypsum. Wetting agents are added to secure an easy and even mix in water, without the problem of flocculation.
Cement paints have very limited colour shade range because only alkali resistant pigments chiefly shades of Iron Oxides are used. Capacity of the cement to bind the pigment particles is negligible, so excessively dark and concentrated shades bleach with the first monsoon showers, developing whitish patches.
Suction capacity of old plaster surfaces, whether virgin or previously coated with cement, lime or oil bound distemper is insufficient to adhere a new cement paint coat. Moreover old surfaces are invariably covered with water-soluble salts which interfere with the adhesion of a cement paint coat. So besides usual sanding and plain water washing, a wash treatment of diluted hydrochloric acid followed by a clear water bath can increase the suction and hence adhesion. Instead of mixing plain water to cement paint powder, use of dull lime water not only enhances adhesion but improves the brush-ability. Cement paints adhere well on sand face plaster surfaces then on plain plaster surfaces.
In many countries masonry public buildings were coated with Cement Paints. Cement Paints re-coating, however becomes increasingly difficult after 3rd or 4th coat. Today Cement Paints are not favoured because other option in the form of Latex or Plastic paint is available. Plastic paints are re-coatable. Plastic paints have a wider range of colour shades, with many saturated and pure colour shades.
Lime white, colour washes and cement paints do not contain any film forming medium. It is the inter-particle cohesion and substrate suction that provide the adhesion to the base and substrate, and resistance to fricative forces. Use of a film forming medium is imperative in many cases. Vinyl emulsion binders are available to overcome such deficiencies. However, uses of such materials create problems of adhesion at the time of re-coating.
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Interior Design Assist 