1-14 BASIC KNOWLEDGE ABOUT PAINTS AND PAINTING Polyester putty is a dual-component paint mainly consisting of an oil-modified unsaturated polyester resin. It becomes hard when mixed with organic peroxides (hardener). This putty is used mainly to correct pores and shallow dents remaining after application of metal putty. It has a very fine and flexible texture and primer-surfacer can be applied directly upon it. But it cannot be applied to form a very thick coat (over 3 mm approximately). Ideally, this putty should not be applied directly over the base metal as it only has a very low adhesive power on metallic surfaces .
.------- -------------------------, ® Polyester putty While the metal putty is used during sheet metal working, the polyester putty is used as a final adjustment immediately before painting. For this reason, it is also called a painting putty and the two putties used to serve different purposes. More recently, however, it has become hard to differentiate the two because makers have developed metal putty having a fine texture and good sanding capacity and polyester putty that can be applied in a thick coat. It is important. therefore, to use putty that best meets the work need and work force.
® Lacquer putty This is a single-component putty mainly consisting of nitrocellulose and alkyd or acrylic resin. It is used mainly to fill shallow sanding marks, pores or dents remaining after the lacquer primer- surfacer application. Lacquer Putty Use of Putty (an Example) (3) PRIMER-SURFACER This is a second coat material that is applied before the top coat application. It has a dual function as a primer and a surfacer, and is used most commonly as an undercoat material during repainting. Modern primer-surfacers are more like a surfacer than a primer, and serve the following purposes: · Rust prevention . . . . . . . . . . A performance required of a primer · Smoothness . . . . . . . . . .
. . A performance required of a surfacer · Prevention of absorption . . A performance required of a surfacer · Adhesion . . . . . . . . . . . . . . . A performance required of both primer and surfacer Primer-surfacer is applied rather thickly to fill tiny dents and prevent absorption of the top coat, and still form a sufficiently thick (30 to 60~-tl coat. It is then polished using a fine sandpaper to prepare the surface for the next process. - 16-