PAINTS & VARNISHESLECTURE# 09

Types of Paints

Matte paint:• is the least reflective sheen available• has a velvety texture• helps hides imperfections in walls and ceilings• offers great depth of color• is generally considered the standard sheen for walls• can sometimes be difficult to clean

Eggshell and satin paint (satin is slightly glossier than eggshell): • have some reflectivity• offer improved durability • are frequently used in demanding environments, like kitchens and bathrooms, where easy cleanup without a highly glossy finish is desired

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Semi-gloss and gloss paint:• are the most reflective sheens• are highly durable and stand up to multiple cleanings• are traditionally used on baseboards, moldings, and doors• can make a statement, but also highlight imperfections

Primer - These may be oil or water based and are used to seal unpainted surfaces to prevent covering coats of paint soaking in. The appropriate type of primer should be used for the surface being painted - wood, metal, plaster or tiles. There are some 'all purpose primers' available which are designed for two or more of these surfaces.

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Undercoat - Usually oil-based, undercoat is applied on top of the primer. The undercoat should be of the correct colour to provide the right colour base for the finishing coats.

Radiator paint - For use on central heating pipes and radiators, it will stand up to the high temperatures without discoloring as other paints are prone to do.

Fire-retardant - These special paints contain an additive to provide a fire-resistant quality, they do not resist fire completely, but has a greater flame resistance than ordinary paint and will reduce their spread.

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Emulsion Paints - Modern Emulsions are water-based, with vinyl or acrylic resins added to make them more hard-wearing than traditional emulsions. This results in varying degrees of sheen in the finish; as the shine increases, the paint tends to be more hard wearing. The ranges usually offer matt, eggshell, silk, satin and full gloss.

Preparation of Paints

A paint is composed of pigments, solvents, resins, and various additives. The pigments give the paint color; solvents make it easier to apply; resins help it dry; and additives serve as everything.

Making the paste - Pigment manufacturers send bags of fine grain pigments to paint plants. There, the pigment is premixed with resin (a wetting agent that assists in moistening the pigment), one or more solvents, and additives to form a paste.

Dispersing the pigment - The paste mixture for most industrial and some consumer paints is now routed into a sand mill, a large cylinder that agitates tiny particles of sand or silica to grind the pigment particles, making them smaller and dispersing them throughout the mixture. The mixture is then filtered to remove the sand particles.

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Instead of being processed in sand mills, up to 90 percent of the water-based latex paints designed for use by individual homeowners are instead processed in a high-speed dispersion tank. There, the premixed paste is subjected to high-speed agitation by a circular, toothed blade attached to a rotating shaft. This process blends the pigment into the solvent.

Thinning the paste - Whether created by a sand mill or a dispersion tank, the paste must now be thinned to produce the final product. Transferred to large kettles, it is agitated with the proper amount of solvent for the type of paint desired.

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Canning the paint - The finished paint product is then pumped into the canning room. For the standard 8 pint (3.78 liter) paint can available to consumers, empty cans are first rolled horizontally onto labels, then set upright so that the paint can be pumped into them. A machine places lids onto the filled cans, and a second machine presses on the lids to seal them. From wire that is fed into it from coils, a bailometer cuts and shapes the handles before hooking them into holes precut in the cans. A certain number of cans (usually four) are then boxed and stacked before being sent to the warehouse.

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