MIL-HDBK-1110
7.3.2
Thinning. Usually thinning to change the viscosity of
liquid paint should not be necessary. A manufacturer formulates
paint to have the proper viscosity for application. If thinning
is necessary, it must be done using a thinner recommended by the
coating manufacturer. Also, the amount used should not exceed
that recommended by the coating manufacturer. Prior to adding
the thinner, the temperature of the coating and the thinner
should be about the same. The thinner must be thoroughly mixed
into the paint to form a homogeneous material. Some "false-
bodied" or "thixotropic" paints are formulated to reach the
proper application viscosity after stirring or during brush or
roller application. Undisturbed in the can, they appear gel
like, but upon stirring or under the high shear of brush or
roller application, these materials flow readily to form smooth
films. Upon standing, the coating in the can will again become
gel-like. Because of this property, thixotropic coatings may
require constant agitation during spray application.
7.3.3
Tinting. Tinting should be avoided as a general
practice. If materials are tinted, the appropriate tint base
(e.g., light and deep tones) must be used. Addition of excessive
tinting material may cause a mottled appearance or degrade the
film properties (e.g., adhesion). Also, tinting should only be
done with colorants (tints) known to be compatible with the base
paint. No more than 4 ounces of tint should be added per gallon
of paint.
7.3.4
Straining. Usually, paint in freshly opened containers
should not require straining. However, mixed paint having large
particles or lumps must be strained to prevent the film from
having an unacceptable appearance or clogging spray equipment.
Straining is especially important for inorganic zinc coatings.
Straining is done after mixing, thinning, and tinting is
completed by putting the paint through a fine sieve (80 mesh) or
a commercial paint strainer.
7.4
Weather Conditions Affecting Application of Paints.
Paint application is a critical part of a complete paint system.
Many of the newer paints are more sensitive to poor application
procedures and environmental conditions than oil paints. Four
main weather conditions must be taken into account before
applying coatings: temperature, humidity, wind, and rain or
moisture. The paint manufacturer's technical data sheets should
be consulted to determine the limits for these conditions as well
as other constraints on application of the paint. Applying
paints outside the limits is likely to lead to premature coating
failure.
103
Previous Page
