If you live in an older home, chances are YOU didn’t paint many of the things inside. You might have changed the color on your walls, but if you didn’t paint the cabinets, bookshelves, interior doors and trim how do you know what kind of paint it is?
I have a bunch of painted trim in my house that needs to be fixed up. In fact, something is soaking through the paint. I don’t want to just paint another layer over the old paint without knowing what it is first, because the results can be disastrous.
First I’ll share a quick tip for how to tell if your paint is oil or latex and then I’ll share tips for how to paint over oil paint with latex and get good results long term. It is possible, but you have to take special prep steps.
An Easy Way to Tell If Your Paint Is Oil Or Latex
The first step before you start any painting project is to determine what you are working with. For the average homeowner it may not be readily apparent if the original paint is a latex-based paint or an old oil-based paint.
The best way to tell if your existing type of paint is oil or latex is to use alcohol or methylated spirits (also called denatured alcohol). You can buy this at your local hardware store or paint store. You can use a cotton ball for this quick test with any paint color other than white. You simply use a cotton ball wet with with rubbing alcohol or methylated spirit and rub it vigorously against a small area of paint for a few seconds. If paint comes off onto the cotton ball or cloth, it’s latex paint.
If you are looking to paint multiple doors in your home, be sure to test each one. This is especially true if you live in an old house. You might be surprised that some doors or rooms are painted with a latex product and some are painted with an oil-based product. Again, you never know if they were all painted at the same time.
If you are trying to test white paint, use a colored, clean rag so you can easily tell if white paint is rubbing off.
Can You Paint Latex Over Oil Paint?
If you paint latex paint on top of oil-based paint without prepping properly the paint will not form a good bond resulting in peeling paint. Oil paint does NOT adhere well to latex paint. If you want to use Latex paint over oil follow these two steps for surface prep before you start painting.
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- Rough up your paint using a fine grain sand paper like 220 or 320 grit. You don’t need to spend a lot of time sanding, just a light sanding to roughen up the surface a little bit.
- Use a primer (if you have time, 2 primer coats are better than one to get a smooth finish). I like to use this Zinsser Bullseye. It is low odor and is a great choice to use over oil paint.
Advantages of Latex Paint
Latex paint has become more prevalent because there are lots of advantages to using it:
- Easier cleanup during your paint job
- Low odor and less fumes
- No yellowing (if you’re painting white)
- Dries faster
The disadvantage to latex paint is that it isn’t as sturdy as oil-based paint. Latex paint chips and scratches more easily. Oil-based paint is also easier to clean once it’s on the surface (not during the painting), which is why it is often used on wood trim, doors and cabinets.
Next time you are getting ready to paint an old door or touch up some of the wood trim in your house, be sure to test the paint first. It it’s oil-based paint It might require some extra prep work.