Paint is any colored liquid which on drying, form a thin surface coat and has specific functions t perform. Paints are used to protect metals, timber, or plastered surfaces from the corrosive effects of weather, heat, moisture or gases etc and to improve their appearance.
Varnish is designed to penetrate the wood, bringing out and enhancing the wood's natural beauty while protecting it from water, dirt, and sunlight.
The main purposes of paint and varnish coatings are protection of materials from damage, such as corrosion of metals and rotting of wood, and decorative finishing of articles. There are also special-purpose coatings (electrical-insulation, fluorescent, temperature-indication, and heat-resistant, gasoline-resistant, and oil-resistant coatings). Paint and varnish coatings are used in all areas of the national economy and everyday life. With proper use, the service life of paint and varnish coatings may be as long as several years.
The properties of paint and varnish coatings are determined by the composition of the materials (the type of film-forming materials, pigments, and other components), as well as by the structure of the coating, which most often consists of several layers. The most important requirements made of paint and varnish coatings are strong bonding (cohesion) of the layers and adhesion of the bottom layer to the substrate, hardness, bending and impact strength, moisture impermeability, atmospheric resistance, and a combination of decorative properties (such as transparency or covering power, color, degree of luster, and pattern).