Veneering both sides...

[mark mcfarlane]

I've read several recommendations to always veneer both sides of 'a piece'. Does this apply to any substrate, e.g. hardwood, bb plywood, mdf,...? What's the physics?

[Jamie Buxton]

The idea is that the veneer is going to expand and contract with changes in air humidity. If you veneer just one face, the panel may cup when that happens. If you veneer both faces, the cupping forces balance out.

Balancing the panel is important if the panel is thin, and if there's little structure in the furniture to hold it flat. A quarter-inch panel in a door is a good example. If the panel is thick, there's more meat there to hold it flat, and if there's structure in the furniture to hold the panel, you may get away with veneering just one face. An inch-thick desk top is an example. But the safe thing to do is to veneer both faces.

[Wayne Jolly]

Just a question for my own edification. You say the veneer will expand and contract, and I agree with that. But it seems to me the big thing is that the layer of glue on the surface that has been veneered will act as a moisture barrier on that side, thus reducing the expansion and contraction on that face. Am I wrong??

Wayne

[Allan Speers]

Just a question for my own edification. You say the veneer will expand and contract, and I agree with that. But it seems to me the big thing is that the layer of glue on the surface that has been veneered will act as a moisture barrier on that side, thus reducing the expansion and contraction on that face. Am I wrong??

Wayne

You are correct. That's the main thing. It's just like finishing or painting only one side.

[Susumu Mori]

For the first time I did veneer (I forgot if I used MDF or plywood for the core), I attached really nice tiger maple I resawed to one face. I think it was about 1/16-1/32 thickness. I knew I had to veneer both sides but I skipped it, just being lazy. I saw the panel immediately cupped. It seems to me, the cupping was caused by the moisture of the glue; either the core or the veneer, or both, reacted immediately. I left it for few days, wondering if it would come back as the glue set, but it never did.

Later, I made veneers from poplar and attached them to the other side. I was amazed by seeing the cupping was removed almost perfectly.

I did this stupid testing only once. So, not sure how much general conclusion I can draw from it, but just want to share it.

[Kent A Bathurst]

...........I did this stupid testing only once........

We call that "Mistaking Your Way up the Learning Curve".

I, for one, have worked hard climbing up the curve, using this exact method.

[Peter Quinn]

Its about balance. Always veneer both faces, or it cups. That pretty much goes for any substrate. Thats why I don't trust those open face sandwiches....I don't want a cupped hot ham and cheese!

[Mike Henderson]

I've experimented with veneering only one side. In fact one experiment I tried was to put multiple layers of veneer on one face and nothing on the other face. Sure enough, the panel bowed. And it got worse with each layer of veneer I put on it (solid wood 3/4" substrate). I tried putting the panel in the sun (veneer side up) to see if the problem was that the veneer side absorbed water and expanded and if the sun would dry out the veneer side. But that did not flatten out the panel.

I put about three layers of veneer on one side before I gave up.

I need to try the experiment again with non-water based glue and see if I get the same results.

Mike

[Alan Lightstone]

I always veneer both sides, and I even worry about cupping if I can only veneer one side at a time, then have to take it out of the press to do the other side. I haven't had cupping when I've had to do that, but I do worry when I have to.

[Chris Padilla]

Due to my design, I had to veneer one side of a double-layer of 5/8" MDF before I could veneer the show side. I veneered shop-cut 1/16" walnut to the MDF sandwich and guess what? Yep, it bowed. I remember measuring an 1/8" rise off my table (veneer on the top) over a 16" wide by about 48" long MDF sandwich. I was quite surprised that such a thin veneer could pull a rather thickish chunk of MDF out of flat but it most certainly did. Always always ALWAYS veneer or more generally, balance or do the same thing to both sides of a panel.

[Jeff Duncan]

It's all about balance, if you take a piece of material and apply finish to one face and not the other you'll experience the same affect. That's why I always try to apply finish to both sides within as short a period of time as possible. There are always exceptions of course….but in general veneers, laminate, or finish, always try to do the same to both sides.

good luck,
JeffD

[mark mcfarlane]

OP here, just thinking this thorough. BTW, I'm not veneering anything, just learning.

Assuming one starts with plywood, it is already veneered on both sides.

If the potential cupping problem is due to ambient changes in humidity, then applying a thin veneer (<1/32) or less) to only one side seems as though it should be OK, there is already veneer on the other side (Although it could have different absorption due to species, cut,... but that would be similar to putting walnut on one side and poplar on the other).

If the cupping is due to moisture in the glue, then perhaps wetting the opposite side of plywood would have the same effect as putting on another veneer.

Just thinking out loud, in public.

[Jason Beam]

OP here, just thinking this thorough. BTW, I'm not veneering anything, just learning.

Assuming one starts with plywood, it is already veneered on both sides.

If the potential cupping problem is due to ambient changes in humidity, then applying a thin veneer (<1/32) or less) to only one side seems as though it should be OK, there is already veneer on the other side (Although it could have different absorption due to species, cut,... but that would be similar to putting walnut on one side and poplar on the other).

If the cupping is due to moisture in the glue, then perhaps wetting the opposite side of plywood would have the same effect as putting on another veneer.

Just thinking out loud, in public.

I wouldn't chance it. Ever. Do to one face the same as you do to the other. Always. There are very few absolutes in woodworking. This is one of them, imho.

[David Kumm]

I agree about not taking a chance but will also share that I have made lots of 8" baseboard by gluing 1/8-3/16" veneer to 1/2" ply. I have not had any cupping but it does help if the veneer is of a wood more stable than the ply layers. Dave

[Lee Schierer]

My father used to make Marquetry plaques with ply wood as the substrate. He veneered both sides and edges and finished all sides. None of his plaques have warped in more than 25 years.