GREY PAINTS.

Press, Volume LXV, Issue 19644, 13 June 1929, Page 4

GREY PAINTS.

PREVENTION OF SPOTTING. PREPARATION OF PIGMENTS. Many ca us have liaa the unpleasant experience of having a well-painted iob commence, within a few weeks, to show light spots as if the tinting colour had faded and usually with complete loss of gloss on these spots. Such spotting occurs most frequently when the paint has been tinted with lamp black, but it also occurs with some other tinting colours, especially ochre, umber, and sieur.a.. The tinting strength or hiding power of most pigments, both white and coloured, varies considerably with the kind of oil or vehicle with which they are ground or mixed. Lamp black, when fully saturated with oil, is a strong tinting colour, and comparatively little is required to tint a large quantity of any white pigment to a deep groy. However. a& the oil is absorbed into the surface, its hiding power is weakened. The white pigment is not so affected, and the result is the .same as if less tinting colour or more white pigment had been used. Grev paint on glass, metal, or other hard, non-absorbent surface will retain its colour almost indefinitely, but on timber, plaster, or other material which will absorb oil, the paint will bleach out just as fast as the oil is absorbed out of the paint film. Verv little of the timber used for weather-boarding and outside woodwork is uniform in grain. In almost every board there are soft or rough spots where the grain is more open and will absorb oil, water, or any other liquid more freely than other parts of the board. It is such spots as these that are the direct cause of the spotting of grev paints. Because white lead tinted with lamp black to a medium or dark slate colour has wonderful hiding power, and one coat will often cover a surface about as well as two coats of white or light tinted paint, a great many people will allow a painter to use only one heavy coat of grev paint. For that reason spotting occurs most frequently on one coat jobs. Paint never wears oown evenly all over a building. It always comes off more in some places than in others, and, if it is chalking, there are bound to be raanv dry spots which will soak up oil as fast as blotting paper soaks up ink. Wherever the oil is *ucked out of a paint, the gloss disappears, the tinting colour loses its strength, and bieached out spots *>how up. The colour of these spots can be restored hv brushing them over with clear linseed oil. That gives the lintins. colour ti-o oil it rcquir-s. and it commences again to work full time. While it is not practicable to use this method afte- the snots have appeared on a finished job, it is a practical way to prevent the spots from anpenring. nnd "an ounce of prevention is always worth a pound of cure." •!1— proper way is to app.y the priming coat in the usual way and allow it to drv hard. Then, berore puttin" on the next coat go carefully over surface and wherever a flat -not firmonis applv ? coafc of linseed ! oil Allow time for this to dry and ! again look carefully over the surface tor further indications of flatting. Sometimes there are spots that are actually spontrv. end one annlication of oil mav not suffice. On a two coat job it is neeessnry to kill all suction before the second coat is applied. On a three coat job handle the priming coat the same wnv as for two coat work, except that only one amplication of oil is made on the spots. Then applv the second coat of paint, and. after' nHswing time for it to get hard, 'jo over the surface agaiu very carefully, oiling such spots as still show.—The "Dutch Hoy Painter,