Post 165 –by Gautam Shah
In Building Industry many different types of finishes are used for covering non-masonry surfaces such as Ferrous Metals, alloys, aluminium, wood, and wood composites. In many cases the surfaces are composed of many different types of materials, textures and forms. Often the extent of each individual type of surface is so small and its composition so complex that it may not be feasible to attend to different surfaces.
Most paint manufacturers offer a General purpose coating systems (GP) for such situations. The coatings are nominally conceived to be multi layer systems (at least of primer, inner and top-final coat). GP coating systems work for the inner and top coat, however, a primer coat is specific for the surface. It is specifically designed for the substrates such as masonry-cement primer, wood primer, mild-steel or iron primer.
GP or General Purpose coatings are used for following situations:
☐ On items that are difficult to coat– Such as deep grooves, undersides, inaccessible areas, narrow stripes, engravings, sharp corners and edges, very smooth surfaces, small parts like lattices.
☐ On locations with difficult access– High level ceilings, external sides of windows in multi storey buildings, roof trusses.
☐ In variable atmospheric conditions– Rain and snow storms, very high to very low humidity environments, dust, sun rays, wind, flying insects, very high to very low temperatures.
☐ In single or multi coat systems– Some initial coatings at plant level as specific coating system and rest on the site as GP system.
☐ For specific purpose– As a fresh system (on a virgin surface), as a re-application system (re-coating with a similar but over an aged surface) or as a renovation system (removal of aged coating layer, repairs and coating).
☐ With peripheral hazards– Fire, chemical vapour and odours, colour dropping or running, and over-sprays.
Such site applicable finishes are designed to dry out at normal atmospheric conditions. Most of the GP finishes allow multiple methods of application, and are applicable in widely variable atmospheric conditions.
GP = General Purpose Paints, as a term are nominally synonymous with Enamel Paints (Oil resin based), but now the term is also used for ‘Plastic’ emulsion paints (Latex paints in American terminology). Such plastic paints are masonry paints for walls, roof-tiles, floors and stage-sets. These are often favoured over oil based enamel paints due to non-glossy (matt) finish and faster drying capacity.