You may have seen a powdery substance on the paint that covers your walls. This is called chalking which is 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. If the paint is exposed to UV rays, then you may see chalking or a powder become evident on the surface.
Chalking is quite common with many types of paint, especially those that are indoor paints that lack any UV protection.
If you see the powder form, especially if you wipe the surface with a cloth, then 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. Each of these plays a role in the process of chalking.
- Color of the Topcoat
- Environmental Conditions
- Amount of UV Exposure
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. This means that you can only expect so much from the paint you purchase.
Why Chalking Occurs?
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 and the result is a powder formation.
To make sure that chalking is happening to the paint on your surfaces, you will need to consider the following factors.
Fading: One of the biggest side effects of UV exposure is the fading of colors from the paint. If you see fading occurring, chances are there will be chalking as well.
You should check by running a cloth over the surface, especially in an area where there is no dirt or grime.
Dirt: When you wipe down a surface with a damp cloth, you may find a powdery substance.
However, this is not necessarily chalking as it might be other elements such as dust, dirt, grime, pollutants, or even salt deposits that have nothing to do with the paint.
On walls, you should wipe them down every so often and check to see if chalking is occurring.
Factors in the Chalking Process
Chalking takes place over time. It means that 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 make the chalking process accelerate.
This means that those who paint the exterior of their beach hours with a thin coat of a dark color can expect it to start chalking rather quickly.
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.
Another is the product itself. For example, if interior paint is used on an exterior surface, then the chalking effect will become pronounced far more quickly because it lacks the elements to delay chalking.
Addressing Chalky and Powdery Finish on Walls
There is no way to reverse the chalking process once it occurs. Once you start seeing chalking on the paint surface, there is no way to reverse the process.
This means that you will instead need to wash, sand, and then repaint the surface with a new batch of paint.
Plus, it is recommended that you apply a UV-resistant coat or have such as coat as part of the paint itself.
If the paint has yet to chalk, there are ways to stop the process from ever starting or at least slow it down considerably.
Several layers of a water-based 100% acrylic latex topcoat will provide maximum durability, especially if the paint is being covered in an oil-based enamel. But there are other methods as well.
a) Inorganic Pigments or Oxides:
Pigments or oxides that are not organic tend to last longer because they are naturally UV resistant. Purchase paints that have inorganic pigments or oxides for the exterior of your home.
b) Use UV Resistant Paint:
This is the most common preventative method in protecting the paint. Proper UV protection means that the ultraviolet rays will not be nearly as effective in breaking down the paint.
c) Light Colors:
Lighter colors not only reflect more light they also tend to absorb less heat and UV radiation. This means that using lighter colors will help the paint last longer.
You should wash the paint annually and repaint it within a certain time period based on the longevity of the paint.
It is better to cover old paint that is still good rather than scraping away paint that is damaged by UV rays and chalking before you need to repaint.
Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for more than a decade to serve the customers in areas such as Charleston, Mount Pleasant, Beaufort, Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques that are being implemented in his profession. You may read more about him here or get in touch with him here.
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