Recommendations for a smooth plywood finish

Piercemeear

Hi,

I'm not really a woodworker, and have a question about finishing plywood I hope someone could help me with. Kind of an odd one.

Working on a project where I'd like to screen print acrylic paints onto a birch plywood (moisture resistant, 6mm) and then finish with a very smooth, transparent surface. The project will be a small run of a kind of kids' boardgame, so durability is desirable and smoothness essential. Finish would want to be clear and to darken the original design as little as possible.

I've been working with some plywood samples this week, sanding to various smoothnesses and giving one, two and three coats of clear polyurethane gloss varnish (by brush). Not really satisfied with the smoothness I'm achieving. If anything the first coats seem to harden any roughness of the surface. Is it just a case of adding more? Or sanding smoother beforehand?

One recommendation I've found online is possibly applying varnish with a foam roller and then using foam brushes to smooth out the bubbles. Have not got my hands on these to try yet.

One point of difficulty is that sanding between coats is tricky, as it damages the ink design that's printed on the plywood.

Should I be looking at some other kind of finish? (I've seen references to epoxy resin online.) Any recommendations? Because I'll be doing something in the order of 50 of these boards, doing many, many coats would probably be too much work. But if that's the only way to what I'm talking about, please let me know.

Thanks in advance for the help.

Hootanany

Spray them

fergal.b

The deck of my boat is plywood and I put 3 coats of epoxy and then about 8 coats of varnish with a roller and then tipping with a brush sanding with 260 wet and dry between each coat then on the last coat I work up the finish with 400 800 1200 2000 wet and then buffed it with rubbing compound and polished with wax, the sides were done the same way giving a piano black finish .
Another way of doing it with no sanding is to just coat it with epoxy and place a sheet of stiff plastic over it and squeeze out any air bubbles and leave it to set then when you peel it off you will be left with a perfect finish, here is a link on how it's done http://duckworksmagazine.com/03/r/articles/glass/bottom.htm

recipio

Firstly, does the board have to be plywood. ? MDF or hardboard will always give a better paint finish compared to ply.
Spraying is the obvious answer. However unless you have the facilities you are into spray cans.
I've found the Chestnut range of finishes ideal for small item finishing. They market a range of sprays but I'd suggest cellulose sanding sealer followed by three coats of melamine lacquer.Sanding between coats with 400 grit will 'denib' the varnish without disturbing the paint layer.Try and blow off any dust with compressed air.
The only agent in the ROI is Raitts in Stranolar in Donegal.( UK suppliers will no longer mail order ) Good people to deal with and they will mail order.
One trick is to immerse the can in very hot water for a few mins. It loosens up the spray and increases the pressure in the can.
Best of luck.

Piercemeear

Thanks all. Board doesn't absolutely have to be plywood, but it's a good price and most importantly looks nice printed. We're kind of basing the thing off an old boardgame we found with a similar finish, probably commercially sprayed?

Thanks for the specific suggestions. I will have to pick up some sprays and epoxy to do tests. I am imagining that spraying would end up costing quite a bit, over a medium-large number of boards. Not sure how affordable that would be.

I'm very curious about the epoxy flattened with a plastic sheet. Looks neat.

All this makes screen printing on paper feel very easy!

Thanks again.

recipio

Piercemeear wrote: »

Thanks all. Board doesn't absolutely have to be plywood, but it's a good price and most importantly looks nice printed. We're kind of basing the thing off an old boardgame we found with a similar finish, probably commercially sprayed?

Thanks for the specific suggestions. I will have to pick up some sprays and epoxy to do tests. I am imagining that spraying would end up costing quite a bit, over a medium-large number of boards. Not sure how affordable that would be.

I'm very curious about the epoxy flattened with a plastic sheet. Looks neat.

All this makes screen printing on paper feel very easy!

Thanks again.

No prob -or should that be no hass !
The Chestnut cans are about 7.50 each - I particularily like them as they give great coverage and don't clog up when left between jobs. Don't buy polyurethane cans - they take forever to dry and are prone to spluttering.

fergal.b

This might also work for you.

Piercemeear

I saw a few videos like that while searching, Fergal. Looks pretty neat. I think I've come across this finish on paintings before.