Applying Latex Paint over Oil Paint

A repainting project raises the old familiar topic of compatibility between oil-based and acrylic paints. June 16, 2014

Question (WOODWEB Member) :
Situation is the GC wants me to prime and spray the first coat of finish on a mantle and very tall mirror frame before install. I would use Clawlock then an interior oil such as Porter Glyptex. Tech. support at both Porter and SW say no problem brushing latex over oil. However I keep hearing that it is going to fail. What's the deal?

Forum Responses
(Finishing Forum)
From Contributor E:
I am not an expert but I believe you could put anything over the Clawlock. It is designed to be a good filling and stable primer. A waterbased comparison would be the General Finishes white primer and the ICA FA452B. I would be confident to finish them on-site with a brushable oil based finish.

From the original questioner:
I'm not the least bit worried about the oil going over the Clawlock. It's the latex brushed on top of the oil that concerns me.

From contributor M:
I would not do it. I am still picking latex paint off my doors/windows and trim after I hired a painter (who told me he was an expert) to put latex over oil. I knew it, he knew it, and he still did it anyway. This was 17 years ago, but there are ways to do it.

From contributor J:
Why not just put two coats of Clawlock on it, then let them topcoat with latex? Get the oil based paint right out of the equation.

From Contributor E:
I just re-read the post - latex over oil will not bond.

From the original questioner:
That is exactly my question! I'm being told by Porter and SW tech. support no problem, but everyone else says no way. So, what’s the deal?

From contributor A:
I used to do a lot of high-end residential repaints years ago. Oil base enamel needs to be scuff sanded at a minimum (it usually needed it anyway). There is also a liquid de-glosser that we used on certain occasions. If I were you I would just spray a universal primer of some sort. When they are field-painted it will undoubtedly be acrylic or latex anyway. Muralo makes great products. Zinnser 123 (acrylic) or Bullseye (white shellac) would work fine for this application. Any one of these would be a lot less expensive than Clawlock. If you have your heart set on oil, spray two or three coats of KILZ, sanding between coats. This is common in a lot of millwork shops around here. Also, have the paint shop tint your primer to the spec'd color and you're all set.

From the original questioner:
Now I'm actually thinking two healthy coats of SW lacquer primer. Then they can brush whatever swill they want on it. I did end up getting a Porter tech guy today that said "no way they can brush latex over oil".

From the original questioner:
To contributor A: It is a straight white, and the guys doing the final paint are very good, I'd recommend them to anyone. The entire issue with this thread was the fact that Porter and SW tech folks said no problem!

From contributor X:
I agree with the others - can't put latex on oil. I was always told that you can put oil on top of latex, but not the other way around.

From contributor F:
There is no inherent defect in the application of latex paint over most anything, including oil base paint. What matters is the preparation and quality of the topcoat paint. As long as your surface is not contaminated and moderately sanded, latex or acrylic paints adhere very well. It is true that oil base paint in general is going to cure to a harder surface and would be considered more durable than acrylic or latex generally speaking. However, any shortcomings of latex vs. oil are differences that exist regardless of whether you apply the latex over latex or oil, lacquer, or whatever. Again, any adhesion failure is going to be about preparation, quality material and applying according to material spec.

From Paul Snyder, forum technical advisor::
You can use latex over oil-based paint without any problems - depending on the brand and product. The manufacturer of the paint you're planning to use can tell you if it's okay to apply the latex over an oil-base product and what preparation is required.

From the original questioner:
The goofy thing is I talked to a different Porter tech. guy and he said no way. So what we came up with is first the lacquer primer undercoater, then a WB version of glyptex which he claims sprays and lays out perfect. Then the painters can brush all the latex they want. The thing that really bugs me is the fact that one Porter Tech. guy says no problem and the next one says no way.

From Paul Snyder, forum technical advisor::
Get a copy of the tech data sheet for the paint you plan to use - that should have the correct information. The waterborne Glyptex sounds like it will work fine. Sometimes sales reps don't have all the answers. The problem is when they answer questions but aren't really sure. It pays to learn where you can find the info you need.