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Painting when it's Hot

The following is information on how hot weather can influence your painting projects.
Sun High summer temperatures are not the ideal time for painting, be it spray, brush or roller. Not only do paints, especially quick drying ones, become difficult to apply, the performance of the coating applied under these conditions may be affected. In addition the safety risks of handling solvents and flammable materials are increased.

Ideally paint should only be applied at temperatures between 15C and 30C. At higher temperatures drying of the paint can be greatly accelerated. This is most commonly seen during spray painting in the form of 'dry spray' or a powdery dull finish. Quick drying finishes such as 505, 520 and lacquers suffer most noticeably from this problem. It can be countered to some degree by the use of slow or retarder thinners such as F-205 or F-215 for enamels and T-19, T-24 retarders for lacquers.

There is a limit to how much improvement you can expect in application however. At temperatures above 35C or so - FORGET IT!. Keep in mind that on a day of 35C that the surface temperature of any object left outside can be much higher than the air temperature and may reach temperatures of 45-50C and higher are quite possible. This being the case the paint dries as it approaches the object. Try painting early in the morning and keep the object inside or undercover until ready to commence painting it.

WARNING: Do not apply paint in confined areas where ventilation is poor and do not spray paint inside a building without proper exhaust equipment and a respirator.

When paint is put on to a hot surface the paint will dry very quickly. Any paint, even water based paint runs a serious risk of being dry before it has had a chance to flow out and wet the surface properly. Whilst the paint may feel dry and look quite ok (E.G. Solarcryl painted on to hot metal guttering) it is almost a certain bet that the adhesion of the coating and thus the durability of it has been affected.

If the paint was already drying as you were applying it - how can it have stuck properly?. This is an important factor to consider with all paints but especially important with primers - 131 Super Bond Etch Primer, 272 Metal Primer, 291 Satin Metal Primer etc and 'no primer' topcoats such as Solarcryl.

Even painting inside a house in hot weather can adversely affect performance - for example when painting new Gyprock or plaster. These surfaces are water hungry and combined with high temperature results in all of the liquids being removed from the paint within moments of application. This means again poor adhesion and lap marks where rolling over and area painted a few minutes previously.

Finally it is essential to consider health and safety. You must use caution handling paints during the hot weather. All paints contain solvents of one kind or another and whilst not all are flammable they do evaporate into the air. In an enclosed space the higher the temperature the more vapour in the air. If they are non flammable there are the usual health risks. If these vapours are flammable then there is an increased explosion/fire risk as well.

Not to mention, any paint left in an open can in the hot weather will form a skin much faster than when the weather is cool. If painting outside cover paint cans and put a small quantity (10-20 mls of the recommended thinner water for water based paints) on top of the paint before closing the can.

Thus painting is something to be avoided as much as possible in the hot weather. If you must paint something please consult our technical department first and remember don't blame the paint for any problems, blame the weather.