extract from Rob Thompson's book
Spray painting is used to apply color and provide surface protection. It can be used to coat most rigid materials. A range of finishes can be achieved from matt to gloss, including soft touch, pearllescent, iridescent and metallic.
Alternatuve and competing prcesses include:
Spray guns are a jet of compressed air to atomize the paint into a fine mist. The atomized paint is blown out of the nozzle in an elliptical shape. The coating is applied onto the surface in overlapping strokes.
Painted surface are nearly always made up of more than one layer. If necessary, the surface is prepared with filler and primer.
Conventional paints are made up of pigment, binder; thinner and additives, The role of the binder is to bond the pigment to the surface being coated. It determines the durability, finish, speed of drying and resistance to abrasion. These mixtures are dissovled or dispersed in either water or a solvent.
Two-pack paints are made of resin and the catalyst or handener.. They bond to the surface in a one-way reaction and are extremely durable.
Qualit: the level of sheen on the coating is categorized as matt, semi-gloss, satin and gloss, High gloss, intense and colourful finishes are produced by the conbination of meticulour surface preparation, basecoat and top coat.
Typical applications: Spray painting is used in a vast range of applications including prototyping, low-volume and high-volume production.
COST AND SPEED Jigs may be required, but this depends on the numbere of the parts and geometry. Cycle time is rapid, but depends on the size, complexity, number of coats and drying time. Labour costs and typically high because these tend to be manual processes.
MATERIALS Almost all materials can be spray painted. Some surfaces have to be coated with an intermediate layer which is compatible with both the workpiece and the topcoat.
ENVIROMENTAL IMPACTS Water-based paints are less toxic than solvent borne. Spraying is usually carried out in a booth or cabnet to allow the paint to be recycled and disosed of safely.