Painting in Cold Temperatures: The Facts
It’s important to understand how low temperatures can affect paint application, namely how it can change the drying pattern, characteristics and performance of the paint. Cold temperatures affect painting because alkyd and oil paints are based on natural oils and resins that at low temperatures become more viscous (they get thicker). So, when painting in cold weather, some paints will become very thick, therefore requiring thinners. Water-based paints are affected mostly by the slower evaporation rate of the water.
Paint may begin to clump and even freeze in the can when the temperature falls too low. For ease of application, it is a good idea to submerge your cans of paint partly in warm water.
Allow for Curing Time
Most alkyd and water-based paints won’t cure properly unless the temperature remains above 10oC (depending on the manufacturer this temperature could be even higher), resulting in a coat that will be susceptible to cracking, fading and chalking much sooner than expected. Lower temperature paints, however, are designed specifically to survive the rigors of winter weather, allowing you to paint all year round.
Paint dries more slowly in cold temperatures, and until the coat is fully cured the temperature must remain above the minimum advised by the manufacturer.
Cold weather will slow drying time and will extend your re-coat times. Re-coat time at 23oC, using water-based paints, requires a period of approx. 4 hours. If the temperature drops to 10oC, then the re-coat time will be extended to approx. 6 hours. Painting in cold weather using alkyd paints will require even more time, in some instances more than 48 hours before re-coating. It is important to note that the surface temperature can differ between various areas on the same structure, causing drying times to likewise vary.
Painting in Cold Temperatures: Problems
- Film cracking
- Poor adhesion
- Improper film formation causing a powdery or weak film
- Lack of stain resistance
- Colour uniformity issues
- Loss of gloss or uneven sheen levels
- Slow drying times because of long exposures to moisture
- Paint will require more mixing time
- If you’re painting onto a surface that has moisture on it, then you’re going to struggle with both application and adhesion
- Touch up coats might look lighter than the base coat
- Excessive film building up might reduce your paint coverage
- Oil-based paint should not be applied when temperature is below 40oC
- Premature skinning of the surface might occur, if the room temperature is raised to create better environmental conditions
- A latex paint film that goes under freeze-thaw cycles during the first two weeks of cure may shorten the long-term life of the paint system
How to Paint in Cold Temperatures: Tips
- Verify that the paint manufacturer recommends the paint for your specific temperatures.
- Pay careful attention to the instructions on the paint tin.
- Check the surface temperature – with a non-contact infrared thermometer – not just the air temperature.
- Make sure you use a good bonding primer before applying paint.
- If required, dry the surface before painting.
- Paints with high quality resins perform better than cheap ones!
- Heat the spray area prior to and during painting
- If moisture is trapped under a coat of paint, it can greatly reduce the longevity of the paint job. So, if the surface remains damp to touch, then don’t paint on it.
- Try to keep the paint warm throughout the day. Paint may begin to clump and even freeze in the can when the temperature falls too low.
- Store paint above 10 degrees Celsius.
Painting in Cold weather may prove more difficult, but with the right tools there’s no need to accept an inferior paint job.