veneering question

[Rick Christopherson]

Its not PB nor MDF. its veneered core. Veneering the back is a waste.

Jack is correct. This is not applicable to a veneered substrate such as baltic birch. Sometimes valid information gets repeated so often that the basis for the information gets lost in the translation. Veneering both sides of a substrate does have a valid foundation, but not for this particular application.

[William OConnell]

Jack is correct. This is not applicable to a veneered substrate such as baltic birch. Sometimes valid information gets repeated so often that the basis for the information gets lost in the translation. Veneering both sides of a substrate does have a valid foundation, but not for this particular application.

I disagree
If you were right I would agree with you
But I still think your a great contributor here and really like your electrical responses to all of the forums Ive seen you on especially way back in the day of Kips place

[Christof Grohs]

It not just the extra thin layer of wood on one side, but the tremendous amount of glue and moisture you will put on that side. It will definitely want to warp. Since its an inch thick, you might get by, but with all the $$ already in the project, it would probably make sense to put some cheap backer veneer on the other side. You can probably find some irregulars on sale somewhere.

Another thought... are you going to frame it? How will you attach it to the wall, any opportunities for something mechanical, like battens, to discourage warping?

I would also add that before someone can tell you it's safe to skip your balancing step on a project of this nature, they may want to take into account the type of glue used to press, the environmental conditions of your home, what type of finish you will use on the panel, will the panel be subject to direct sunlight, etc... IMO, this panel should be balanced using the same adhesive with perpendicular grain orientation. I think it is not the fact that the panel will have an even number of plys which will cause problems, rather the issue becomes the adhesive. If others here have built a panel of similar size, left unbalanced and not experienced panel warping they should consider themselves quite lucky.

As Jesse mentioned, a frame would not be a bad idea for this large of a free standing panel. Maybe then you could get away with an unbalanced practice.

[David DeCristoforo]

"Jack is correct. This is not applicable to a veneered substrate..."

So sorry but I'm afraid Jack is not correct. Nor are you. If you (or Jack or anyone else) want to lay up veneers on one side of your substrates, you are certainly welcome to do so. But you run the risk of ending up with warped panels and for that reason, this is "bad" advice to offer the OP.

[Thomas S Stockton]

I'm with David on this plywood panel veneering is one of the places that warping is a major problem. A lot of it has to do with the fact that you are introducing a whole lot of moisture into one face of a panel through the glue you are using unless it is epoxy or contact cement and contact cement is just plain bad for veneer work. To poster who was worried about the expense, backer veneer is cheap about 50 to 75 cents a square foot so it would add maybe $20. If I had to redo something for a client it is going to come out of my pocket and redoing a large project can be expensive.
Tom

[jack duren]

I layed $1000 worth of rift sawn veneer Wednesday for a law firm. Guess I better go cover the back side so I dont get sued by the law firm or the architects

[Bob Wingard]

Since this entire thread is based on opinions rather than absolute facts .. I'll stand by mine.

Adding 0.025" of veneer to a sandwich of 24 or more plies would not introduce any tremendous warping forces. The excessive moisture referred to does not exist .. it will equilibrate and evaporate through the face of the veneer in short order. The moisture simply does not reside in the wood for all eternity.

I expect the next advice would be that the two panels of BB ply must be glued-up with their faces cross-banded to each other, bu then, the front & back veneers would be 90 deg to each other, and we can't have that !!

Backing a panel for balance is normally a good, if not required procedure, but for this application, I think it is a waste of time, money, and any other resources expelled.

But then, that's just my opinion.

[Nancy Laird]

The current issue of Woodshop News (as yet unavailable on-line) has an interesting article by Bob Flexner on finishing both (or all) sides of a piece--the bottom line is that finishing all sides of a piece is a relatively new idea and has no basis in fact. All one has to do is to look at furniture (antiques) built in the 1700s and 1800s and inspect to see if the undersides of table tops, etc., have the same finish at the top---most don't, and one doesn't see the exaggerated warp/cupping that one might expect, based on current "rules." "Until the 1920s and 30s and the introduction of sprayed lacquer, both sides were rarely finished. If it were important to do so, you'd think furniture makers over the previous two or three centuries would have figured it out." I have a piece of furniture in my house - a child's roll-top desk - that I got from Santa in 1951 - and there are parts of it that are not finished on both sides. It is as good a shape today as it was 56 years ago.

Bob Flexner is probably well-known to most of you as an expert on wood finishing, having written several books on the subject and a contributing editor to Popular Woodworking. I think he knows of which he speaks. The quotes in this post are directly from his article.

Bob's comments above are right on - any moisture will be evaporated in short order and the warp/cup just won't happen, particularly not with veneer-core ply. "Cupping occurs on single-sided veneered panels because of the use of a water-based adhesive. The water swells the veneer as it is being laid. When the veneer then dries out, it shrinks, drawing the panel into a mildly cupped warp. There is no cupping when solvent-based contact cement is used to attach veneer to just one side."

Again, just my .02.

[David DeCristoforo]

"...the bottom line is that finishing all sides of a piece...has no basis in fact."

Again, I would have to disagree. I have spent a lot of time repairing warped and cracked panels and tops on many of the very kinds of pieces mentioned. Maybe not every panel made this way will warp or crack. But it's still a bad practice. Furthermore, not all furniture was made this way. I'm sure that for every example you can find, I will find another that's done the other way. Just because you read it in FFW does not make it an unarguable fact. So, make your panels with veneer on one side only. Maybe you will get lucky, maybe not....

[richard poitras]

I've sometimes wondered if you could just use butcher paper on the back of a project like this (shiny side out). It would provide strengh, and the wax covering on the outside would balance whatever finish you applied to the front. Thoughts?

Cary

I think your idea would work Cary ..

[Frank Drew]

There is no cupping when solvent-based contact cement is used to attach veneer to just one side."

Well, that's a bad practice (contact cement w/ veneer), which calls into question his other advice, at least in my mind.

[Rick Christopherson]

"...the bottom line is that finishing all sides of a piece...has no basis in fact."

Again, I would have to disagree. I have spent a lot of time repairing warped and cracked panels and tops on many of the very kinds of pieces mentioned. Maybe not every panel made this way will warp or crack. But it's still a bad practice. Furthermore, not all furniture was made this way. I'm sure that for every example you can find, I will find another that's done the other way. Just because you read it in FFW does not make it an unarguable fact. So, make your panels with veneer on one side only. Maybe you will get lucky, maybe not....

This statement tells me that you didn't read the OP's discussion very carefully. Either that, or you are applying your thoughts regarding one type of substrate to ALL substrates. If you are seeing cracking in a veneer on a veneer-core substrate, it was the veneer that failed or was faulty, not the substrate. I suspect your statement was referring to a veneer placed over a solid lumber core, or some other unbalanced substrate, but not VC, and certainly not high-density VC.

The expansion and contraction forces from a thin veneer surface are not sufficient to impact the stability of a veneer-core substrate.

When a substrate warps due to imbalanced surface veneer, it is not the veneer that causes the warping (unless it is plastic veneer). It is the imbalance of equilibrium within the substrate resulting from a barrier being placed on one surface and not the other. This is most applicable to an MDF substrate in a moisture rich environment.The tensile forces in the veneer are insufficient to affect virtually any substrate. High density veneer core plywood is specifically chosen for its expansion/contraction stability.

Well, that's a bad practice (contact cement w/ veneer), which calls into question his other advice, at least in my mind.

Blindly saying that contact cement with veneer is a bad practice is shortsighted and due to a lack of experience. There is merit to that statement, but only as it applies to non-backed veneer. Manufacturers of paper-backed veneer actually recommend the use of contact cement, and suggest not using PVA glues.

[Dave Tinley]

Sorry david, but I have to agree with Jack and some of the others on this.
The so called rule of veneering both sides is open to interpetation, with regard to type and thickness of substrate and how the finished product will be utilized. 99 percent of the time when I veneer a project and use 3/4 or thicker materials I will not use a "balance" veneer. And never have I had a cupping or splitting problem. This goes for mdf, veneer core or lumber core plywood. If I use 1/4" plywood I will use a backer veneer if its going to show, ie inside a door, or its not going to be in a frame. But if its part of a frame and panel where visability is not important, I wont use a backer veneer.

Since the OP is going to have a 1" thick substrate I see no need or advantage to applying a balance veneer.

[jack duren]

All we use is contact adhesive for veneers in commercial unless the prints call for something else....

[David DeCristoforo]

Well this is all fine. I'm not trying to tell anyone what to do. It's just that I hate to see anyone risk a problem by not doing something as simple as skinning the back of a veneered panel or something as foolish as using contact cement on "raw" wood veneers. I've just seen too many problems with these things and IMMHO the fact that someone may get away with it now and then still does not make it "good practice". So, I will remain on this side of the argument, you guys can support the "opposition" and the OP can take which ever advice he wishes.....