Post 547 by Gautam Shah
Architectural finishes are coatings or paints that are more often than not, applied on the site, before and after the elements have been assembled as an architectural entity. These usually dry out at ambient temperatures -air drying, i.e., are non baking types. Architectural finishes, in comparison to ‘industrial coatings’ are high pigment & extender build coatings. Substrates for architectural coatings are of THREE basic categories, 1. masonry, 2. wood, wood composites and fibrous surfaces 3. metal. In few instances architectural finishes are also applied in the industrial set-up, over systems, components and parts.
Masonry structures are in the form of straight or inclined walls, columns, piers, abutments, and occasionally on roads, curbs and floors. A masonry structure could be made up of unitized blocks of compacted clay, stones, cement concrete or baked clay or bricks with their patterns of joints and joining materials. Masonry surfaces may have plasters of plain or rendered faces of clay, pozzolana, lime or cement, all strongly alkaline in nature.
Masonry finishes, are of TWO basic classes: Exclusively protective coatings and Decorative finishes. Few commercial finishes provide both the qualities. Decorative finishes may be sub-classed as Interior and Exterior coatings, where the later category may offer substantial protection advantages.
Masonry surfaces cover very extensive area, and so water has been the ideal vehicle for formulation and also as an application solvent material. It is abundant and cheaply available and is non toxic. Water as a vehicle, however, has no binding characteristic, and for that reason many natural and synthetic adhesive type of gums and resins are used as binders. Where such substances are not dissoluble in water, various water-based emulsions are used. Latex paints or emulsion type plastic paints form the main section of such coatings for masonry finishes. On removal or evaporation of water, the film formed maybe substantially moisture or gas impermeable, or a permeable lattice in the form or water repellent coating.
Voids over masonry surfaces are partially filled or levelled, causing a change in texture of the surface, when such coatings are loaded with pigments, extenders and fillers. In few instances this is unavoidable, but in many cases improvised `architectural’ or `rendered’ effects are intended. Fillers for such `rendered’ coatings include natural or treated mineral particles, quartz and silica sands, mica dust, glass and polymer beads, metal-dust, flakes, chips, or shavings.
Some of the architectural coatings are:
Among the other masonry finishes, water proofing finishes constitute a major section. Such coatings are either `technical’ coats or part of multi purpose coatings. Technical coatings, impermeably seal the surface by covering all voids, pores and crevices; or cover the surface in the form of a lattice that is non wetting and so water repellent. In the former case the coatings are used where water vapour pressure is low and where a change in texture (due to filling up of voids ) is allowable, or desired. In the second case, texture properties of surfaces remain more or less intact, while the water repellence is provided by the ionic quality of the surface. Commercial water proofing coatings are based on Bitumen, epoxidized bitumen, PU coatings, silicone paints, and polymeric compounds.
Good film properties on masonry surfaces are achieved by using 100 % acrylics, or copolymers of ethylene, or acrylic esters, emulsions of vinyl copolymers. Chlorinated rubber with a suitable plasticizer, has a good alkali and atmospheric contaminant resistance. Long oil alkyd enamel with appropriate primer system work well for masonry surfaces.
Floor paints are used to improve the appearance, increase abrasion resistance, reduce moisture penetration and impart spillage proof qualities. Medium oil alkyds and moisture cured polyurethane, epoxy compounds, chlorinated rubber coatings are used. Road marking and curb coatings are very similar to floor paints except that in certain cases reflective or fluorescent pigments are used. Hospitals, operation theatres, pharmaceutical and electronic assembly plants, require joint less flooring and wall-finishes for bio-pathological reasons, or for dust less environment. Such finish systems are made from of chlorinated rubber, urethane or epoxy coatings. Wood or wood composite floorings in athletic and indoor sports area require a smooth, non skidding and spillage proof coating. Such coatings consist of melamine, urethane or epoxy materials.