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The surface condition of the wood to which
the finish is to be applied can substantially
affect the performance and hence the life
expectancy of the finish. The following
procedures should prove helpful:
New Wood
New wood such as cedar siding and trim,
should be protected from the weather before,
during and after construction. It is seldom
necessary to carry out extensive surface
preparation providing the wood has not weathered
for more than two weeks and is clean and
dry. If it has been contaminated by dirt,
oil and other foreign substances they must
be removed.
For smooth-planed, flat-grained cedar,
some surface preparation may be desirable.
On flat-grained wood, the surface should
be scuff-sanded with 50-60 grit sandpaper.
This procedure will greatly increase the
coatings performance but will not detract
from a smooth finish. Surface preparation
is not necessary for textured cedar.
Weathered New Wood
Weathered new wood that has been exposed
to the elements for longer than 2 weeks
may have a degraded surface that is unsuitable
for painting. Preparing the surface by sanding,
brushing, and washing before applying the
finish is recommended.
Paint Finishes
Paint finishes must be removed if the old
surface is severely peeled, blistered, or
if cross-grain checking has occurred because
of excessive paint build-up. The removal
of a film-forming finish is also necessary
if a penetrating stain or water-repellent
finish is to be applied to a previously
painted or solid-color stained surface.
Note that changing from a film-forming to
a penetrating finish sometimes does not
give satisfactory results because residual
paint inhibits absorption.
Finishes can be removed by sanding, wet
sandblasting, pressurized water spray, electrically
heated paint removers and chemicals. Although
quick and easy, sandblasting and pressurized
water spray are not recommended unless extreme
care is taken to avoid damage to the wood's
surface. Special precautions to ensure worker
safety must be taken if the old paint is
lead-based.
Weathered Water-Repellent
Preservative Finishes
Weathered water-repellent preservative finishes
should be cleaned with a non-ferrous bristle
brush to remove loose fibers and dirt. If
the surface is soiled, it may be scrubbed
with a mild detergent solution. If mildew
is present, it should be controlled. The
surface should be thoroughly rinsed and
allowed to dry completely before refinishing.
Caution: Never mix bleach with detergent
containing ammonia as the fumes can be harmful
or fatal.
Weathered Penetrating
Stains
Weathered penetrating stains on mildew-free
surfaces are relatively easy to refinish.
Excessive scraping or sanding is not required.
A stiff, non-ferrous bristle brush may be
used to remove surface dirt, dust and loose
wood fibers before applying the stain.
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| Here, the image of
naturally aging cedar is counterpointed
with solid-stained splash areas and
densely whitened window and trim boards
|
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| The unifying effect
of a solid-color stain is used to good
effect on this residential housing complex |
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