Polyurethane Finish over Oil-Based Paint

It works well, but be aware of the re-coat window. March 9, 2006

Can an oil base paint be coated by a polyurethane clear coat finish? What would the process be to correctly coat this project?

Forum Responses
(Finishing Forum)
From contributor R:
I would suggest just scuff sanding the oil based paint and apply poly.

From contributor J:
I agree with Contributor R. I would also suggest using a barrier coat between the two.

From contributor M:
I've been doing it for years without a barrier coat and it’s worked well for me.

From contributor D:
This can be done very successfully with little to no risk of adhesion issues. The only problem with doing this is when you sand the color coat the clear has no way of wetting into the scratches like in wood finishing.

Paint is just different. The best success I have found in doing this is to contact the paint manufacturer and ask what the minimum recoat window is. In other words you want to know how quickly you can put the poly over the freshly painted oil, without sanding and without causing the oil to wrinkle.

In most cases I have been able to spray my oil base, and come back in 45-60 minutes and spray some poly or poly/varnish over it. If I wait longer than that I have to wait 16-24 hours and then sand. You get the picture. This I believe is known as the critical recoat window. You can top coat this at this time or you have to wait until this time to do so.