Paint chalking is the formation of fine powdery substances on the surface of the paint due to exposure to the elements. All paints chalk to some degree as a normal way for the paint to self clean. However, excessive chalking can cause color fading and is a sign of paint failure. In dry arid climates where there is little rain, like Phoenix, paint chalking has a tendency to happen more quickly than other parts of the country so proper paint preparation and maintenance is crucial for a long lasting paint job.
We find it more prevalent on stucco, masonry, metal, and masonite siding substrates, but it can affect plywood siding and dimensional lumber also. It is solely an exterior paint issue. The highly exposed areas facing East, South, and West should be inspected, and be very mindful of the upper areas where the UV-rays have less obstruction.
As well as looking faded, severe chalking also makes repainting a problem because the extreme porosity of the surface powder adversely affects adhesion and doesn’t allow the paint to bond directly to the surface. Instead the paint bonds only to the chalky powder and will be a skin of paint not properly attached to the substrate. Once a little time lapses, even within a few months, the results can be large popping of the topcoats in sheets or multiple small areas of peeling. Once major popping occurs, the only fix is to remove all loose coatings down to a sound substrate, usually with a large pressure washer, causing a huge paint chip mess. MTS has tricks to reduce the mess this type of prep creates, and I may share some of those in a future blogpost. Of course, the best way to avoid the mess is to prep the surface properly in the first place.
- Wipe surface with hand or dark cloth to determine the extent of chalking.
- Obtain ASTM D4214 Standard Test Methods for Evaluating the Degree of Chalking of Exterior Paints.
Causes of Excessive Chalking:
- Extended exposure to the sun’s ultraviolet rays.
- Over thinning or overspreading paint.
- Not using the proper primer.
- Using a low-grade paint.
Excessive Chalking Solution:
- Hydro-wash all surfaces to be painted using at least 2600 PSI pressure washer. Sometime twice if heavy chalk still remains.
- Once the surface is completely dry, prime chalked surfaces using special sealer/primer to lock down remaining chalk for proper adhesion.
- Use a high-quality latex paint to repaint.
Taking on a project like this (especially if you own a large home) can be a difficult and sometimes heights can make it a dangerous task. Don’t take the chance of getting hurt or missing important paint preparation, call MTS Painting and our expert painters will bring your home’s exterior back to life.
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