I know this topic comes up often, but didn’t find anything matching in a search…
I do quite a bit of vacuum pressing of shop cut veneer (~3/32 thick). Usually to a 1/4 -> 1/2 substrate of MDF or plywood. I always veneer both sides.
However I now have a project with will involve a plywood box enclosing 5 drawer compartments. (See pic)
Since the inside will be maple which is available in a good enough plywood quality for this purpose; I’m wondering if I use a thicker ply – say 5/8″ if I could just veneer one side. I will be using shop cut veneer.
I would be veneering the individual pieces before assembly.
Anyone have any success with this or viewpoints?
Thanks!
carl
Replies
If you use Unibond or another adhesive without a great deal of water the results are not too bad. I completed a project not long ago where I did not like the grain match between two cherry boards, so I veneered one side with a shop made 3/16" thick piece of cherry veneer. I mocked up a couple of samples, one with Unibond and another with PVA. The PVA sample was unusable after it came out of the press (about a 3/8" bow over a 60" long piece), but the Unibond version only had a slight bow. I bet you will find even less bow since your substrate is ply. You might want to complete a trial or two first.
I know many will mention that it is a not recommended to do one sided veneering, and I agree, but this is a case where it does make sense. You are basically copying what engineered flooring manuf do all the time. The difference is most of them use PUR (heat activated) adhesives.
Good luck
If memory still works, seems like typical response on vacu-press veneering forum is that veneer more than about 1/8" thick starts to act like solid wood. Your plan should avoid that problem.
Gluing only one side will create unbalanced stress, which may or may not come back to haunt. The image shows some long parts where bowing could become noticeable. Having a back will help resist, but without a face frame to further restrain there is a chance of some bowing, even with thicker ply.
Don't think anyone can offer a guarantee, so you'll have to balance the risk of bowing against extra work of veneering both sides with similar material.
I'd try some sample panels. Should not work. But it might. I've never done it.Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
The concepts of unbalanced stress (and, unequal moisture absorption) when veneering just one side of solid wood, and too-thick veneer behaving like solid wood make sense. But, if the thin-ish veneer is being applied to (high-quality) plywood, wouldn't the veneer behave like just another layer of the ply? Seems to me that the plan just might work.
Not sure if it will. Plywood is made with an odd number of plies, to even out stresses I think. Add one new ply and now there are an even number of plies. Plus, the previously stable and flat plywood now has one new layer of cured glue.
My suspicion is that gluing veneer on just one side will unbalance the stresses in the plywood, and the only issue would be whether the plywood (and how it is braced in the piece of furniture) is strong enough to resist the unbalanced stress.
On second thought, you might well be correct. One of the points of plywood is having a balanced number of plies with grain running in the same direction, but opposite to the next underlying ply. Adding the veneer, essentially another ply, would unbalance that, potentially causing the sheet to bow.
Having done a little vacuum press veneering, I can tell you that even using a backer veneer does not guarantee a flat panel. It is not only the stress of the shrinking veneer that causes warping. Warping is also caused by uneven drying time. My first project, I made my own veneer from curly, ambrosia maple and a backer veneer from plain ambrosia maple. The panels came out of the press looking great. I stacked them on my bench, stickers, panel, stickers, panel. The top panel warped concave side up. The top of the top panel had unrestricted drying while the other sides of the panels were restricted by each other and the bench.
When they make plywood, they always use an odd number of plys, as mentioned, to keep the number of glue lines even. They always use a backer veneer of the same thickness as the face veneer to equalize stress.
If I were going to try veneering only one side of a panel, I would dampen the back side of the panel before gluing the veneer on. I would restrict the drying of the veneer by placing it on stickers face down on my bench. This might keep the stresses even. I would also place weight on top to help keep it flat while it dries, and I would let it dry like that for a week or two. You can generally get a slightly warped panel to lay flat with some moisture, weight and time.
All-in-all, it's much more predictable to veneer both sides at the same time and make sure all sides of all panels dry at the same rate.
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