Published on March 1st, 2016 | by Grant Barnard0
Can I Paint Water Based Over Oil Based Paint
Painting over oil based paints with latex or waterbased paint is one of the biggest arguments among even some of the most experience painters. Some will say you can paint with a water based paint and some will say use a primer. Now, do you us oil primer or water based primer?
At Grants Painting we test every paint system to make sure that our painters are doing the best work possible. If you are local to Indianapolis, contact Grants Painting at 317-800-4540 or schedule an online estimate now on our homepage.
First, Lets Know The Materials
- Old School Oil Enamel – This is the true non alkyd oil paint that would have had a horrible smell and a super slick surface
- Alkyd Oil Enamel – This is the more recent oil based paints. These do not have as much sheen as their higher VOC “Old School Oil Enamels”
- Alkyd Oil Primer – This is the general oil based primer available most states and most stores.
- Cheaper “Latex Paint” – Cheaper latex paints are made of several components such as vinyl products as binders. These are interior paints that generally you will find under $20 a gallon and will advertise for great hiding at a low cost and mainly as the contractors low or mid grade versions.
- High Quality Acrylic Paint – High quality acrylic wall paints are paints like Valspar Signature Series(Lowes), Pittsburgh Grand Distinction(Menards), and well nothing at Home Depot… honestly.
Is it Oil or Water Based Test
The test is simple. Use any type of alcohol, denatured is the best but not needed. Vodka and rubbing alcohol will work for this test just as well. Use a rag that is of a different color than the paint. With the rag soaked in alcohol try to wipe the paint off with a few good wipes and elbow grease. Especially some of the newer waterbased paints will seem like an oil but will then dissolve after a bit more persistence. If the alcohol will not dissolve the paint then it is an oil based paint.
The Adhesion Test
An adhesion test is always a good idea and can save a ton of work and headache. Sand down one single area and then apply your intended paint system. You can also do two spots to test different primers or the use of one at all. After painting your single spot, let it dry a full 24 hours in good condition. Then place a small “X” slit in the paint film with a knife. Place a piece of blue 3m tape over the area, press down real good and then slowly remove the tape. The tape is usually expected to rip out the center of the X but anymore and you may want to consider a new paint system or method.
Can I Paint Water Based Topcoat Over Oil Enamel
There are two basic types of oil enamel. The first is alkyd which is the later and greener version of oil based paints. Alkyd enamels are easier to paint over especially in today’s time of water Based hybrid alkyd topcoats and oil modified waterborne acrylics. True oil enamels will typically fisheye any water Based coating and this will be discovered during your adhesion test. A paint fisheye will look like a tiny area on the surface is literally pushing paint away from it. A fisheye is less about an adhesion failure and more about surface tension.
To paint over alkyd oil enamels usually a very high grade waterbased topcoat will paint right over the surface. You MUST completely sand the surface. We would typically use an aggressive sand paper followed by a sanding block to smooth out the surface for painting.
To paint over true oil enamel you must sand and prime with an oil based primer. Several water Based enamels will paint directly over an oil based primer. Read below for more information on this.
Can I Paint Water Based Topcoat Over Oil Based Primer
Yes, of course you can. In fact many topcoats will specify an oil based primer as an option for painting over certain types of wood. However cheaper interior paints will tend to have issues with painting over an oil based paint. More expensive waterbased topcoats that have some type oil modified technology will, of course, have a better time going over an oil primer. Its best to check the Technical Data Sheet(TDS) and sometimes other paperwork such as sell sheets to find recommended primers. If there is an oil based primer on the list then obviously you’ll be just fine. However, the oil based primer MUST be totally dry before a waterbased coating is applied. There is no point in then applying a waterbased primer because you can just find a compatible topcoat for less additional cost than a gallon of water Based primer.
Can I Paint Oil Based Topcoat Over Water Based Topcoat
No, There is no reason to paint oil over a waterbased coating. Applying the much less flexible oil coating over the more flexible water Based coating WILL make the coating separate very quickly depending on temperature change. Additionally water can also move through the water based coating and then stop at the oil based coating causing moisture damage to separate the coats.
Simply find a better water Based coating to go over top if you are interested in improving durability.