It is important to distinguish the type of paint that is currently on your building before you put on another coat of paint. If you use the wrong type of paint, you could find it peeling a week or so later. This could be a very expensive proposition since good paint can cost upwards of $40 per gallon.
Oil and Water Based
You may remember from your high school chemistry class, that oil and water do not mix. All paints and stains are either oil or water based and when they are combined, the results can be disastrous.
More specifically, water based paints cannot stick to the oil based product, thus it runs or peels. Since water paints sit on the top of the surface, the oil based products are not able to penetrate the wood and never set.
The Transparency Test
Most oil based paints are designed to sink into the wood. Stains and varnishes can easily be detected by examining the surface of the building. If you can see the wood grain and the stain simply colors and enhances the wood, it is an oil based product being used.
However, more and more non transparent stains are being used. These stains still sink into the wood, but they give the appearance of paint by covering all aspects of the surface. For this reason, the transparency test can be trusted to determine transparent oil based products, but should not be the only method for determining solid or semi-transparent paints.
The Goof Off Test
Since some oil based paints exhibit the same characteristics of water based paints, the Goof Off test should be used before any painting is done.
Goof Off and similar products remove all types of things, such as grease, markers and latex (water based) paints. Buy a bottle of goof off at your local hardware store. There are other brands available, just make sure it says that it removes latex paint.
Douse a rag with a little bit of goof off and find an inconspicuous place on your wall to test. Start scrubbing the wall with the wet part of the rag (wear gloves). If the paint starts coming off, it is a water based paint. If the paint is already peeling, make sure that you see evidence that the goof off is actually breaking down the paint. The paint will bubble or look as if it's melting or wet.
Converting Oil to Latex
You may want to use latex because it is much easier to work with. Many older houses have oil based paint since that was primarily used in the past. If your building is covered with a solid oil based paint, you will have to use a primer first. The primer will bond with the wall and provide a surface for the latex paint to stick to. When you go to your paint store, make sure you tell them you are covering oil based with a latex paint and they will make sure you get the right primer.
Autor: Jason Capshaw
Added: August 1, 2009