You may have seen a powdery substance on the paint that covers your walls. This is called chalking, which is usually caused by a degradation in one or more elements of the paint that is applied.
Such degradation is often caused by exposure to ultraviolet or UV rays, Which means if the paint is continuously exposed to UV rays, you may see chalking or a powder become evident on the surface very fast.
Chalking is quite common with many types of paint. But it’s especially noticeable with indoor paints that lack any UV protection. If you see the powder form when wiping the surface with a cloth, you can expect that UV radiation has something to do with the chalking process.
However, the overall rate that the paint decays will depend on several factors such as environmental conditions, amount of UV exposure, and color of the topcoat. Each of these plays a role in the process of chalking.
It is true that many outdoor paints include elements that prevent blistering, peeling, or flaking. However, the chalking effect can take place even with the most protected of paints.
This is because the environmental conditions are not within the control of the paint manufacturer – you can only expect so much from the paint you purchase.
Why Chalking Occurs?
As I just mentioned, most chalking is due to exposure to ultraviolet rays on the paint. The UV rays from sunlight interact with the paint and cause the resin or binder within the paint to break down. This allows the pigments to be lifted from the surface, resulting in a powder formation.
To confirm that chalking is happening to the paint on your surfaces, you must consider the following factors.
Dirt: To check for chalking on painted walls, wipe them down regularly and inspect them. Many times when you wipe a surface with a damp cloth and see a powdery substance, it may not be chalking. The substance could be dust, dirt, grime, pollutants, or salt deposits that are unrelated to the paint.
Fading: One of the biggest side effects of UV exposure is the fading of colors from the paint. If you see fading on the walls occurring, chances are there will be chalking as well.
If you suspect a chalky substance on your walls (especially in an area where there is no dirt or grime), check by running a cloth over the surface. You will most likely find chalky powder on the cloth if UV exposure is causing the problem.
Other Factors in the Chalking Process
Chalking takes place over time and is not an overnight phenomenon. Also, any initial exposure that does not last long shouldn’t have an effect. However, as time progresses, the chalking effect becomes more pronounced if the following factors are in play.
- UV Radiation
- Extreme Temperature Variations
- Coastal Environment
- Dark Colored Paints
- Thinner Coat
All five factors play an important role in whether chalking forms on the paint. While UV radiation is the primary cause, other sources can accelerate the chalking process to the point where it becomes visible very fast.
While all exterior paint is exposed to UV rays, if the exterior is also subject to one or more of the other factors that contribute to chalking, you will need to be more diligent and add more protective factors to the paint itself.
For example, those who paint the exterior of their beach house with a thin coat of a dark color can expect it to start chalking rather quickly (because of high humidity and extreme temperature variations) compared to a lighter color using a thicker coat.
Another is the product itself. For example, if interior paint is used on an exterior surface, the chalking effect will become pronounced far more quickly because it lacks the elements to delay chalking.
Addressing Chalky and Powdery Finish on Walls
Once you start seeing chalking on the painted surface, there is no way to reverse the process. This simply means that you will instead need to wash, sand, and then repaint the surface with a new batch of UV-resistant paint.
If the paint has yet to chalk, there are ways to stop the process from ever starting or at least slow it down considerably.
a) Use UV Resistant Paint:
Proper UV protection in the paint product means that the ultraviolet rays will not be nearly as effective in breaking down the coating and chalking it.
a) Inorganic Pigments or Oxides:
Purchase paints that have inorganic pigments or oxides for the exterior of your home, as they are naturally UV resistant and tend to last longer.
c) Choose Lighter Colors:
Light shades not only reflect more light, but they also tend to absorb less heat and UV radiation. This means that using lighter colors will help the paint last longer.
d) Topcoat with Acrylic Latex:
Besides the above, it’s good to apply several layers of a water-based 100% acrylic latex topcoat that will provide maximum durability, especially if the paint is covered in an oil-based enamel.
e) Repaint Instead of Scraping the Old Paint:
You should wash the paint annually and repaint it within a specific time period based on the longevity of the paint.
It is better to cover old paint that is still good rather than scraping away the paint damaged (by UV rays and chalking) before you need to repaint.
The Bottom Line
Chalking can be a frustrating problem to deal with, but it doesn’t have to be. With the proper steps, it’s possible to keep chalking from ever becoming a major issue in the first place.
In any case, it’s important to take action as soon as you see powdery walls so the problem doesn’t worsen. Right paint and proper maintenance will slow down the process and keep your walls looking great for years to come.
Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for over a decade serving customers in areas such as Charleston, Mount Pleasant, Beaufort, and Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques implemented in his profession. You may read more about him here or get in touch with him here.