When painting trim, doors and cabinets, you should sand latex paint in between coats for a smooth, glossy finish. How long you should wait depends on the factors that affect the drying time such as temperature and humidity. The sheen level and even color of the paint make a difference in drying time as well--dark colors dry more slowly because of the larger amount of slow-drying pigments. If you're careful and use the right sanding materials, you can paint, sand and re-coat latex in a day.
Paint Properties
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Read the paint label. Most latex paint can be reapplied in 4 hours, but not all formulas are the same and you'll need to wait longer for some paints. You can sand the paint after it's dried long enough to be re-coated. Take both the thickness of the paint film and the color into consideration. A coat of paint applied with an airless sprayer will be heavier than a coat of paint applied with a brush, and darker colors dry slower.
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Drying Conditions
Allow extra time if the humidity is over 80 percent or the temperature is below 65 degrees Fahrenheit. Ideal drying temperatures are between 70 and 80 degrees, with humidity below 70 percent. A dehumidifier or air conditioner will help speed paint drying time indoors. There also needs to be some air movement to help evaporate paint. When working inside, open windows or use a fan. When working outside, avoid painting when it's very windy. The paint may dry faster, but it will also be contaminated by dust, pollen and bugs that blow onto the wet surface.
Sanding Latex Paint
Use 120- or 150-grit sandpaper or a fine to medium flexible sanding sponge to sand fresh latex paint. You can use coarser grits for sanding cured latex paint, but it takes up to 30 days for latex paint to cure completely hard and coarser grits will scratch or remove fresh paint. Sand with a light touch. If the paint is colored, you may see some color coming off on the sandpaper. This is fine, as long as the paint itself isn't being sanded off. Use a damp--not soaking wet--rag to wipe sanding residue off before applying your next coat.