Exterior Applications Alkyd house paints are alkyds mixed with oils to make them more flexible for exterior use. This makes them too soft for porch paint and if used indoors, will tend to yellow more than regular alkyd paints. Surfaces should be cleaned and painted before chalking becomes excessive. If left too long, the surface will deteriorate and complete removal, priming and repainting will be required. Dirt will promote the growth of mildew, and all exterior surfaces should be washed periodically, especially in humid areas.
Dark colours absorb much more heat than light colours.
Siding can warp, and sap may be drawn out, causing the paint to peel. Black paint causes cracking and cupping of wood in direct sunlight. To determine if a painted surface is latex or alkyd, rub the paint with nailpolish remover. To estimate the number of coats of paint on a surface, measure the thickness of a paint chip with a micrometer. The solvents in alkyd primer will raise the nap of the drywall paper, requiring extra sanding before re-coating.