Poly Over Acrylic/Enamel

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The A Train

New User
Adam
I'm new to the forum and I'm glad I found it. I try my best with a few projects, but I never had much training in wood working. I am building a table out of an old sewing machine. I was able to salvage some small wood scraps that I arranged and flushed with the rest of the plywood. I have a pic to show what I mean. The tabletop has been cut, sanded, and painted. I want to poly over the center portion; and I would also like to keep it uniform and poly over the paint as well. The paint is an Olympic 100% acrylic exterior enamel. The poly I have says it is water based. Would I run into any problems poly'ing over the entire piece? Any other suggestions for me?

Thanks!
 

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Bryan S

Bryan
Corporate Member
First thing Adam, welcome to the site. Now, to try and answer your question a Google search brought up this thread from here.

http://www.ncwoodworker.net/forums/showthread.php?t=23706

According to our resident finishing Guru Howard Acheson, yes you can and as far as finishes go, when Howard talks we listen. You will find his responses toward the end of the thread. Hopefully Chris, who started the thread will chime in with the results.

Please stop in the Who We Are forum and formally introduce yourself.
 

kooshball

David
Corporate Member
I have used latex paint on bar stools before then topped them with clear, waterbased polycrylic from Minwax with good results..that was 7-years ago and the stools still look unused.
 

Berta

Berta
Corporate Member
You want to use water based poly. Non-yellowing, or it will color the paint. I always use water based varnish over my painted pieces. It is clear and you can find it in indoor/outdoor.
 

yellofins

Ron
Corporate Member
I use Minwax Polycrylic over the Olympic exterior enamel for my cornhole boards. I would suggest making a test piece to see how the paint and finish work together Leave some of the wood unpainted and cover the painted and unpainted area with the clear. I have only had one color of paint that bled into the clear coat. (ECU Purple.....)
 

Jeff

New User
Jeff
Adam, welcome to NCWW. You're project is looking good and congrats on that.

The link provided by Bryan is also a good read.

The poly I have says it is water based. Would I run into any problems poly'ing over the entire piece?

Poly is a generic term which can mean polyacrylic or polyurethane, both of which are available as waterborne products and they're non-yellowing when compared to oil based finishes. Some of the newer polyacrylics also have a bit of polyurethane added for improved durability. Your paint is acrylic so a clear acrylic topcoat is consistent. What's on the wood inset?

It's always good to try complete finishing on scrap pieces before committing to the final piece. Most of these "poly" products recommend light sanding between coats for adhesion of the next coat.

https://generalfinishes.com/retail-...rs/polyacrylic-waterbase-topcoat#.U61iFyi-o23

https://generalfinishes.com/sites/default/files/file_downloads/Tech-Data-EF-PolyAcrylic-062805.pdf

Here's a brief primer on waterborne finishes and how they work in general.

http://www.thewoodwhisperer.com/videos/waterborne-finishes-hvlp/
 

The A Train

New User
Adam
Thanks for the responses guys! Here is a link to the polyurethane that I have. http://www.lowes.com/ProductDisplay...gId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

the consensus seems to be that this would work. I believe water based polys are much thinner and I will need several coats, am I correct? Also, the plywood that I used was just a birch ply from lowes; but I'm not sure on the inset portion. I plan on lightly sanding out some of the brush strokes from the painted portion, cleaning it all with some mineral spirits and then applying my first coat of poly.
 

Howard Acheson

New User
Howard
In spite of the confusion paint and finish manufacturer's saddle the inexperienced use with, both your paint and clear finish are acrylic based. You can scuff sand your table top with 320 grit paper and then brush on a couple of coats of an acrylic clear finish.

But you may have a non-finish issue to be aware of. I can't tell exactly but it appears that the center part of the table top is solid wood blocks and the "white" portion is plywood. If so, you have created a cross grain situation. The solid wood portion will want to expand across the grain direction with changes in seasonal relative humidity. But, the plywood will not expand and contract thereby constricting the expansion/contraction of the solid wood. This will lead to glue line failures and warping. Nothing will prevent this destruction over time.

In the future, be aware that solid wood will always expand and contract across its grain direction while composition material like plywood, MDF and other composition materials will not. The two can not be directly mated.

If you are new to woodworking, I suggest you get a book titled "Understanding Wood" by Bruce Hoadley. Amazon will have it. This book will give you all the info you need when working with wood.
 
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