polyurethane over acrylic paint?

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merrill77

Master Scrap Maker
Chris
It is an oil-based acrylic that I just applied today. Can I top-coat it with an oil-based poly? It's still a little tacky now (painted it at ~3p). If it's dry tomorrow am I good to go? Or should I wait longer? Based on what I recall from Flexner I think I should be ok...but though I would consult the wisdom of the list.

TIA!
C

p.s. My googling returned a variety of answers :(
 

Joe Lyddon

New User
Joe Lyddon
I made a knife holder and painted a little ditty on the front of it with Black Acrylic paint; this was black on white.

After letting it dry, I applied water based poly on top of it... The Black acrylic smeared over the white background.

So, I would think there would be an interaction... how it would be in your case, I don't know.

Try it on a piece of scrap... to find out for sure. Let us know if it works & you like it, OK?
 

DaveO

New User
DaveO
Why do you want to top coat an oil-based acrylic paint with Poly? The paint is going to be as durable or more than the Poly. Plus with the addition of the Poly refinishing options become much more difficult. With just paint, you can repaint at any time, Poly with have to be stripped or heavily sanded, it don't even like to stick to itself.

Dave:)
 

merrill77

Master Scrap Maker
Chris
Why do you want to top coat an oil-based acrylic paint with Poly? The paint is going to be as durable or more than the Poly. Plus with the addition of the Poly refinishing options become much more difficult. With just paint, you can repaint at any time, Poly with have to be stripped or heavily sanded, it don't even like to stick to itself.

Dave:)

Well, I don't actually want to topcoat the paint. But if it won't cause problems, then I won't have to mask off all the painted areas :> It's a shop cabinet with some bare wood areas and some painted areas. Refinishing is not likely ;)
 

Joe Lyddon

New User
Joe Lyddon
I was doing it just to give everything on the front more protection; it was a white background primer with a Black acrylic figure over the white.
 

Berta

Berta
Corporate Member
I paint lots of my projects. You will not need the poly. Also oil based poly will yellow your white.
 

Howard Acheson

New User
Howard
I want to make the same point as Berta, an oil based poly varnish will cause an amber cast over your white paint. If you want to overcoat with anything, I would suggest using a waterborne clear acrylic. While waterborne acrylics are not quite a tough as an oil based poly, they ain't far from it and should be just fine.
 

Joe Lyddon

New User
Joe Lyddon
On my project, the white was just a white primer, no real protection to speak of... and I painted a black acrylic image on it. I felt the primer should have better protection... Yep, maybe a better acrylic White would have been better, but I just grabbed what I had & used it. :gar-Bi

I used water based poly... it smeared the black acrylic. :gar-Cr

I wasn't aware there was a Clear Acrylic... will check that out...

Thank you.
 

dkeller_nc

New User
David
Well, I don't actually want to topcoat the paint. But if it won't cause problems, then I won't have to mask off all the painted areas :> It's a shop cabinet with some bare wood areas and some painted areas. Refinishing is not likely ;)

In general, I think this is a bad idea. Besides the yellowing, polyurethane is notorious for not adhering well to anything except bare wood. I've made a few bonsai stands with 12-16 coats of oil-based poly on them followed by wet sanding and buffing to get a "piano finish". I finally succeeded in this, but it was a nightmare. Every successive coat of poly left witness marks when sanded down - evidence that the successive coats didn't bond all that well.

If it's a shop cabinet, I would suggest the following - if you're OK with a bit of yellowing on the wood, then wipe on two or three coats of Watco danish oil on the bare wood. Wiping it should make it easy to keep it off of the painted surfaces, and if you get a bit on it during application, you can just wipe it right off. The other option is get a can of Zinsser white shellac and coat the whole project. The white shellac is bleached and will have very little yellow to it, and shellac will stick to anything, including acrylic, polyurethane, laquer, etc. White shellac is not stable, so make sure you get it in-date on the can, and that you don't buy much mroe than you need.

Clear acrylic is also a good option, but unless you've spray equipment, it can be hard to get on surfaces without leaving very obvious brush marks. It can be thinned with no more than 10% water - any more and it will coagulate. If you want it thinner, you need to buy a water-based thinner expressly made for the purpose. You can get it at Jerry's Artarama, by the way.
 

Howard Acheson

New User
Howard
>> I wasn't aware there was a Clear Acrylic... will check that out...

Minwax Polycrylic, General Finishes Polyacrylic, etc. Any waterborne clear finish is acrylic.
 
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