This issue of the PQI
Contractor Newsletter is the seventh of a
series illustrating the performance benefits of top quality
interior and exterior paints. The information can be
helpful for reducing chance of complaints or call-backs,
and illustrating to customers the importance of using
quality paints.
Illustrating
Performance Benefits of Quality Paints:
Resist Cracking on Wood
Background: Wood
is a relatively unstable surface: it expands and contracts
as the atmospheric temperature and humidity change.
And the unevenness of the grain can make the dimensional
changes non-uniform. For a paint job to be resistant
to cracking, it must have a degree of flexibility,
and
excellent adhesion to the surface.
Factors to be Taken Into
Account:
 • All
bare wood should be primed with a quality acrylic
latex or alkyd wood primer; latex primers will
provide tannin stain blocking, and better resistance
to mildew and cracking, long term. Oil-based
(alkyd) primers will provide maximum
stain blocking over wood having exceptionally
high tannin content. Quality acrylic latex paints
may be applied over either type primer.
• Crack resistance of primers and paint
are directly related to dry film thickness (DFT).
Accordingly,
these coatings should be applied in a heavy coat,
and not spread thin. Typically, a spread rate
of not over 450 sq. ft./gallon is appropriate
for wood primers and paints.
• Some species of wood are more prone to crack paint than others. Softwoods
such as southern yellow pine and longleaf pine with very pronounced grain are
more
difficult than more homogeneous grain woods like western red cedar and redwood.
Edge (“vertical”) grain wood is better for crack resistance, compared
with “flat” grain wood, all else being equal.
• Wood that has been exposed to the weather for more than a few weeks is
more likely to exhibit paint adhesion loss and more cracking than is unweathered
wood, or
weathered wood that has been refreshed. Also:
- Weathered wood examples: wood repairs left
unpainted; wood left exposed by failing paint;
wood never painted
- Weathered wood can be refreshed prior to painting by sanding; or for decks
by careful power washing with plain water or by use of deck treatment products
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Click on the image above to
open the printable PQI sheet illustrating the quality
paint benefit of Better Resistance to Cracking
compared with economy paint.
To see sheets on other quality paint performance
benefits, please visit the Quality
Paint Page on the PQI web site.
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PQI News:
The Rohm and Haas Paint Quality
Institute will be at the upcoming PACE (Paint
and Coatings Expo), January 29 – February
1, 2006 at the Tampa Convention Center in
Florida. Stop by at our booth and say hello, and
share your
thoughts,
questions and suggestions. Information about the
convention is available at:
http://www.pace2006.com
Just as in 2005, PQI will author articles on paints and painting in various publications
next year, including American Painting Contractor. Topics will range from the
latest color trends to tips on getting the most from quality paints and stains.
Q & A:
Q: I
know not to use interior paints outside for durability reasons, but what about
using exterior paints
indoors – is
there any problem with that?
A: This
question comes up from time to time, mainly from do-it-yourselfers,
but it can be helpful for contractors,
as well. We recommend against using exterior paint indoors.
There can be lingering odor from the paint that can be
quite disagreeable. An exterior paint may not tend to
flow out as well as the interior counterpart, so brush
and roller marks can be a problem. Also, the paint may
take longer to dry and cure, so surfaces may stick to
themselves (“block”), such as a painted door
sticking to the painted door jamb. Q: A customer scraped the fender of his car against
some garage trim, and got white paint on the car. How
can he remove the paint? It is latex, applied about
a month ago.
A: If there isn’t a large area involved and the
white paint is just on the surface of the car’s
paint, he can try rubbing the latex paint off with
some denatured alcohol on a small piece of cloth. But
he should first test the procedure on an unnoticeable
area of the car to make sure that it does not damage
the finish. Caution the person to wear suitable eye
protection, and solvent-resistant gloves. Denatured
alcohol should be used with ample ventilation, and
kept in a child-proof container, away from heat and
sources of spark or flame.
Industry News:
Growth of remodeling
activity slowed moderately in the third quarter of
2005, according to the National Association of Home
Builders’ (NAHB) Remodeling Market Index. Third
quarter results receded from the seasonally adjusted
second quarter of 2005, but remained in the positive
growth range. “A softening of the overall rental
market has led to an acute decline in rental remodeling
expenditures,” said Remodelors™ Council
chairman Don Novak, a remodeler from Cedar Rapids,
Iowa. “Remodeling activity remains strong for
owner-occupied units, driving the continued positive
outlook.” Owner-occupied housing represents 69%
of total housing in the U.S.
The Rohm and Haas Paint Quality Institute
P.O. Box 1348
Philadelphia, PA 19109
215.592.3000
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