Painting over oil or latex?
Question:When painting a wall, how could you tell if you are painting over oil or latex?
Answers:
You can do a small test patch on your wall to determine if it is oil based or a latex paint. Take a rag or cotton ball dip it in rubbing alcohol and rub a small area ( in a less visable spot ) on the wall. If you see some of the colour come off on the rag or cotton ball, that will indicate that it is latex paint.
When repainting any walls, it is recommended that you apply primer first, especially if you are repainting with a dark colour. An extra coat of paint does not take the place or do the the job of a primer. Primer, unlike paint, covers and seals in the existing layer of paint to prevent it from bleeding through the new paint. It will also seal in stains, and can retard mildew growth, while providing a "fresh canvas" for the new paint to "float" on, instead of being sucked into the old paint layer. If using a dark colour, ask to have the primer tinted and it will reduce the number of coats needed to achieve the coverage and depth of colour. To tint it, they will usually put the amount of colour used in a litre of that colour, into a gallon of your white based primer, so it will be a lighter version of the same shade.
If you find you have oil based paint on your wall, that doesn't mean you have to continue to use oil when repainting. There are excellent primers you can apply over oil that will then allow it to take a latex paint. With today's latex paint and primer formulations, there is seldom a need to put up with the odor and difficult cleanup of an oil based paint, even when you are going for a glossier finish. Ask your paint dealer for more guidance, they are the experts and will be happy to help you.
Good luck, I hope this helps.
This is easy.
1) You have to prime over old paint every single time or the new paint will not stick.
2) Use a primer that works on both oil paint and latex paint. (any paint store sells this)
3) You can use any top coat paint on this primer.
4) You won't need to know what the old paint was made of to make this work.
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