These asphaltic paints dry by evaporation only. They are more weather resistant than corresponding
coal tar paints because they do not alligator, but they are inferior in water resistance. Since the solvents
used in their manufacture are mild, they do not give taste to water coming in contact with them.
Consequently, asphaltic paints are frequently used in painting steel tanks and concrete reservoirs storing
drinking water. These paints may be reinforced with inert fillers to make very thick, durable coatings
giving protection at low cost against severe corrosive conditions. They are, at the same time, very weather
resistant, because the fillers minimize the degradation of the asphaltic components against the rays of
the sun. If the inert fillers consist mainly of finely divided cork, a heavy coating that has insulating
properties can be applied to cold service substrates, such as refrigeration tubing, and this will prevent
condensation and sweating.
Asphaltic varnishes are made from such natural asphalts as gilsonite, with or without the addition of
resin, by cooking with drying oils. The resultant varnishes are durable. Their lasting qualities depend on
their oil length, that is, the more oil incorporated (up to a certain limit), the more lasting the varnish
will be. Their use, of course, is limited by their black color.
Bituminous colored paints are made out of asphalt varnishes by pigmentation with strong dry colors.
Since the varnish to start with is deep brown, only comparatively dark colored paints can be manufac-
tured. But their extreme durability and low price make them very valuable coatings. They exhibit excellent
resistance to industrial fumes, condensation, and the destructive action of sunlight. One drawback is the
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