1. Reduction of Finishing Materials
Improper thinning is one of the most widespread abuses
of painting and almost invariable produces inferior
or unsatisfactory results. Painting materials are delicately
balanced formulations which produce correct hiding,
levelling, drying, lustre, colour retention and durability.
Unauthorised, excessive, or incorrect thinning upsets
the balance of a formula and most often causes a shoddy
paint job.
Explicit directions for the use of the material are
printed on the label of each can of Pratt & Lambert
paint, varnish, enamel and other products. If a product
is designed to be reduced by the user, the exact amount
of the particular thinner to be used is definitely
specified. If no reduction is specified, the product
should be used exactly as it comes from the can.
2. Stirring of Pigmented Products
Insufficient stirring, both before and during application,
often causes unsatisfactory results. Pigment particles
are heavier and gravity causes them to layer out. In
storage and in use, pigments have a tendency to settle
and reduce the normal pigment-vehicle balance. Unless
the coating is thoroughly mixed prior to application
and during use the paint or stain will not hide properly
and the finish colour will be off shade. Stirring of
settled material is more easily accomplished by first
pouring the liquid off into another container. The
paste in the bottom should be stirred and the liquid
poured back while stirring continues. Stirring penetrating
stain products is very important both before and during
application.
3. Temperatures and Atmospheric
Conditions
Low Temperatures.
Paints and varnishes are temperature sensitive, but
Pratt & Lambert products are formulated to permit reasonable
latitude of safety factor. The ideal application temperature
is 70° F (21° C). Lower temperatures and cold
surfaces increase viscosity and thicken the paint.
The products do not brush quite so easily and heavier
coats result. This fact, coupled with the slower evaporation
of solvent, may result in runs or sags on vertical
surfaces or wrinkling. The gloss of the finish may
also decrease due to the low temperature. At temperatures
below 50° F (21°C), the resin or emulsified
particles in latex tints do not fuse together to form
a film. This results in a tender film lacking in adhesion,
washability, or durability. Catalysed coating are particularly
sensitive to low temperatures. Many types will never
cure if the surface temperature is below 50°F (100°C).
High Temperatures.
Elevated temperatures decrease viscosity and thin
the paint. The paint or varnish becomes more fluid.
They brush more easily and thinner coats result. Again,
runs and sags may be evident because of their greater
fluidity. The gloss of the finish may also decrease
when subjected to high temperature.
Humidity.
In general, paints or varnishes dry more rapidly
and more uniformly when the humidity is low. Moisture-laden
air is less receptive to the evaporation of solvent
than dry air and can retard their drying. This may
result in the finish drying with a lower gloss and
also allows dirt and dust to settle on the film or
result in wrinkling.
4. Ventilation.
Ventilation should be provided during and after the
application of any coating. Ventilation helps remove
the volatile portion from the film. A strong draft
may affect the uniformity of lustre of interior enamels
and varnishes. A freshly coated surface should be protected
from a strong draft.
5. Mildew.
Mildew or mould is a minute plant organism of a parasitic
nature which grows on surfaces supplying food (organic
material such as wood, certain paints, textiles, paper).
Warm, dark and moist conditions are favourable for
growth of mildew. Mildew is often confused with other
stains such as gas discoloration, dirt or rust. It
is usually recognisable by the following characteristics:
a. Mildew has a blotchy appearance. The discoloration
is not uniform.
b. It is frequently powdery and almost always present
as a surface condition.
c. It occurs in localities and situations where atmospheric
humidity has been persistently high or where the underlying
surface has been damp.
Mildew bleaches out if it is touched with a few drops
of household bleach. Dirt and gas discolorations are
not affected.
Complete sterilisation of the surface is needed before
painting. Bare or painted wood should be scrubbed with
the following solution:
Household bleach - 1 quart Powdered non-ammoniated
household detergent - 1 tablespoon Add warm water to
make 1 gallon Rinse thoroughly and allow to dry Be
sure no water is left in crevices Paint promptly to
avoid reinfection.
CAUTION: Household
bleach may cause eye and skin irritation. Use in
well ventilated areas. Wear appropriate protective
equipment (eg. safety goggles, neoprene rubber
gloves and boots).
