When it’s hot and windy, paint starts to lose water to evaporation as soon as you pour it into the applicator’s bucket. It’s OK to reconstitute the paint with as much as 10 percent water (and if you’re spraying, you may need to). But thin in batches—don’t thin the same bucket all day or you’ll end up with more water than paint. After each break or after lunch is a good time to thin another batch.
Direct sunlight heats up the substrate and causes paint to dry quickly—maybe too quickly. Work on the south side early in the morning, get the west side done before the sun reaches it, and work on the east side in late afternoon when it’s had a chance to cool off, or early in the morning.
Place some ice cubes in the painter’s bucket before inserting the liner and filling with paint. The ice-water jacket around the liner will keep the paint can cool while it’s hanging off the ladder in the sun, extending the paint’s working life in the can and allowing crucial extra minutes for the coating to dry at its ideal rate.
Hot, windy weather is paint’s enemy. Heat and low humidity accelerate evaporation—and when paint dries too fast, the binders and pigments can’t coalesce and interlock as well, and the protective paint film may not be as durable or flexible. Ideal application temperatures range from 50 F to 80-plus F, but when temps climb to 90 F and above, paint suffers.
To beat the heat, we asked painting contractor Nigel Costolloe of Boston-based Catchlight Painting for a few tips:
Rule No. 1 Stay out of direct sunlight and follow the shade around the building.
Rule No. 2 Thin paint responsibly. Paint evaporates in the bucket, and it’s OK to replenish the lost water. But limit the added water to 10 percent, and thin down only what the painter can use before his next break. (Keep the rest covered in the shade.) Better than water, thin using an extender formulated by the manufacturer to match the carrier in the paint.
Rule No. 3 Ice down your can. Drop a few ice cubes into the bucket before inserting the liner and filling with paint. An ice bath will keep the paint cool so it doesn’t thicken before it’s brushed on.
Floetrol, from Flood Corp., is a generic extender suitable for many paints that uses the same ingredients found in typical paint formulas, minus the pigment. But paint manufacturers also can supply extenders that are custom-formulated to match a particular brand of paint. In hot weather, extenders help the painter keep a wet edge longer, for a more uniform appearance after drying.