Before you begin that painting job, there is one very big decision you need to make. Do you go with oil-based paint, or with water-based paint? How will you know which is the better choice? Which paint should you use when painting over a surface that has already been painted? Which is best for painting exterior surfaces? Which is best for painting interior surfaces?
Water-based paint definitely has some advantages over oil-based paint. For one thing, water-based paint is quicker to dry than oil-based paint. Another advantage to water-based paint is that it won’t show stroke marks as distinctly. In addition, it is easier to clean off than oil-based paint. For many people, of course, the biggest advantage of water-based paint is that it doesn’t permeate the room with the strong smell that oil-based paint does.
On the other hand, if the exterior surface over which you plan to paint was previously painted with oil-based paint, you should go ahead and repaint with the same kind. The problem is that latex-based paints is more susceptible to the expanding and contracting that climate changes cause than water-based paint and therefore if you use a water-based paint to cover an oil-based paint you are running the risk of the undercoating peeling beneath your shiny new paint job. If you are planning to paint an exterior surface that hasn’t yet been painted, go with latex exterior paint. In this way the surface will be better able to breathe. In addition, the latex exterior paint will adhere better during climate extremes.
When using latex paint, also be sure to test for whether the chalk from the previous paint job has been removed. To do this, paint a smaller area of the surface just as in the test above, only this time use two coats. And instead of waiting a few hours, you’ll have to wait a couple of days. After two or three days use a paperclip to scratch a line through the paint, then stick some clear tape over the line and quickly remove it. Check the tape for paint specks. If more than a handful of paint specks are stuck to the tape, that means the paint isn’t bonding strongly. This means you’re going to need to do either one of two things. You’ll have to make sure you thoroughly clean off the chalked paint. Or you’ll need to switch to an alkyd paint. Alkyd paints do a better job of covering up chalk.