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Paint and water don’t mix.
Can You Paint in Humidity?
Yes, you canpainta house in humidity, though this depends on the level of humidity.
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you might paint a house in the 40- to 50-percent humidity level range with optimal results.
A 70-percent humidity level is the maximum level for most paints.
At a 80- to 85-percent humidity level, the paint will not cure.
Below a 40-percent humidity level is not recommended, either, since paint does need enough moisture to cure.
While it seems reasonable to assume that more dry conditions help paint cure better, this is not true.
When the paint dries at a slower rate, brush marks have a chance to flatten out.
Paint Flashing
Paint flashing is the blotchy or uneven appearance of paint after it has dried.
Paint that is allowed to dry slower will level out its brush marks and the sheen will remain consistent.
Paint needs to dry at a steady rate to properly cure.
Relative humidity levels in the 70-percent zone will drastically slow drying and curing.
But these humidity levels will still not prevent you from painting altogether.
They simply make the job more difficult and painstaking.
The paint will sit on the surface and remain in that gummy state.
Efforts to dry the paint with heat may not be successful.
It is strongly discouraged to paint when the RH level is above 80- to 85-percent.
Measuring Relative Humidity
Check the weather report for predicted relative humidity levels.
No place is evernothumid.
How Humidity Slows Paint Drying
Humidity does not have to bar you from painting.
In other words, which will dry first?
Tip
Water needs to evaporate at a rate as fast or faster than the solvents.
If the water interferes with solvent drying, then the paint cannot form a hard surface.
It becomes a one-way path, a painting disaster that cannot be solved under current conditions.
The only solution, then, is to strip away that gunky, wet paint and start fresh.
Usingoil-based paintswill not help, either.
Oil-based paints will encounter the same problems as water-based latex paints.
The Best Time of Day to Paint
Start painting early, but not too early.
Painttechnology has evolved in recent years to the point where the painting window has enlarged considerably.
This window is controlled by factors such as ambient temperature, season, and direct sunshine.
It’s tempting to wait until temperatures are higher to begin painting.
The result may be surface staining, poor adhesion, and premature peeling.
But the story is different when it comes to uncoated, natural wood.
Your window of available painting time shrinks.
Is Interior Painting Affected by Humidity?
Interior surfaces can be affected by humidity.
But indoor spaces can be conditioned and controlled, while outdoor spaces cannot.
Interior paintingis a different matter, so interior walls are rarely affected by humidity.
Interior conditioning means that humidity levels can be controlled.
Interior surfaces are protected and should not be subject to moisture settling overnight.
Why House Paint Fails.Forest Products Laboratory,USDA Forest Service.
