CHALKING
Possible causes
McPherson Quality Painting and Water Proofing
PROBLEM
Chalking is the formation of fine powder on the surface of the paint film due to weathering. Chalking can cause color fading. All paints chalk to some degree, it is a normal, desirable way for the paint film to wear away and provide a good surface for future repainting.
Generally, alkyd paints chalk more quickly and to a greater degree than acrylic latex coatings.
On most surfaces, especially white, slight chalking is helpful because dirt is washed away with the chalk when it rains.
Medium and heavy chalking will cause tinted paint to lose its color and become lighter. Severe chalking makes repainting a problem because the extreme porosity of the surface powder will adversely affect adhesion and does not provide the paint a sound surface to bond to. This is particularly true with water based paints which tend not to penetrate and therefore will bond only to the surface powder.
Quality paints may chalk mildly, but still maintain a sound surface that will not crack and retains good moisture and weather resistance for many years.
CHALKING
Possible
causes
Extended exposure to the combined effects of moisture and the ultraviolet rays of the sun.
Using a low-grade
paint. Overthinning the paint. Overspreading the paint. Not
priming and sealing a porous surface.
SOLUTION
1.)
Rub the painted surface with a finger or dark cloth to determine
the degree of chalking.
2.) Remove all chalk residue.
Extremely severe chalking requires pressure washing or
sandblasting. If a pressure washer is not available, use a stiff
brush, a mild detergent and spray the chalky surface with a
strong stream from a garden hose.
Moderate and lightly chalked masonry surfaces may require wire
brushing or sanding to remove the excess surface powder. Spray
the chalky surface with a strong stream from a garden hose.
3.) Allow surface to dry thoroughly.
4.) Rub the surface with your finger to check if any chalk
residue remains.
If little or no chalk remains, and the old paint is in good
condition, then no priming is necessary.
For moderate and lightly chalked surfaces add Aqua-Prime (W 613) to
the first coat of latex paint. 100% acrylic finishes provide
better chalk resistance than vinyl acrylic water based paints.
If
noticeable chalk still remains, use Masonry Surface Conditioner
under the finish coat, or apply a primer, such as BIN 123
Waterborne Primer.
5.)
Repaint.
If there is chalk washdown on brick:
1.) Scrub the bricks with a stiff brush and detergent solution.
2.) Use a strong stream from a garden hose to rinse.
3.) If the brick is a CHALK slightly different RUN-DOWN color after it
dries, rub a piece of brick over the area or paint the area with
a brick colored coating.
THANK YOU FOR VISITING.
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