veneering question

[tyler jones wa]

I glued 2 half inch sheets of 5 foot by 5 foot baltic birch together to make a 1 inch thick sheet. Next I am veneering a layer of quilted maple to one side to cover the entire surface. It will have a inlay design in the middle of it and will hang on the wall

So my question is... normally I would veneer both sides of something - like a cabinet door. But, I dont want to waste 25 sq ft of veneer on the back which will never be seen. Do I need to worry about the panel warping in this case? what should I put on the back that would be inexpensive, or should I just leave it?

thanks...

[Dewey Torres]

The general rule is ALWAYS veneer both sides for stability. It is perfectly acceptable to use inexpensive veneer for the "non show" side.

Dewey

[Don Inghram]

I'd definately cover the back with some kind of a veneer. Surely you can find something cheap. Think you'll be asking for trouble if you don't. JMHO.

[tyler jones wa]

The general rule is ALWAYS veneer both sides for stability. It is perfectly acceptable to use inexpensive veneer for the "non show" side.

Dewey

what if I used something like a door skin on the back, or does it have to be the same thickness as the front veneer?

[Jim Becker]

Any inexpensive wood veneer product will be fine for the back side...door skins included. Use the same glue that you use for the show side.

[Cary Swoveland]

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

[jack duren]

#1 the baltic birch already has a veneer and #2 you only need seal the back as you would the front....

[David DeCristoforo]

"#1 the baltic birch already has a veneer and #2 you only need seal the back as you would the front...."

Not exactly. You are correct that "out of the box", the "backs" of the sheets are veneered in the same manner as the "fronts". However, once an additional layer of veneer is added to one side, the balance is lost. The "rule" with veneering is that you treat both sides equally and, with the exception of material quality, this includes thickness and to a lesser degree, species. Violate this rule at your own risk....

[jack duren]

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

[Matt Hutchinson]

I don't know whether or not the back has to be veneered, but I am wondering if the backer used on the opposite sides of laminate (formica) covered tables would work, or maybe that's too much of a "sealer"? I used to work in a woodworking factory, but we did a lot of lay-ups with laminates and backers. It's a rather cheap material, I just don't know if it's the proper one for this application.

Hutch

[Bob Wingard]

Your Baltic Birch already consists of about 24 layers of veneer .. .. .. adding one more to the front, I don't think will cause any harmful "imbalance".

[Jesse Cloud]

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?

[David DeCristoforo]

Jack, Matt and Bob....

Not meaning to argue, but your statements are simply not correct. It does not matter how many layers there are or if the core is MDF, veneer or whatever. Veneering the back in not a "waste".

[jack duren]

No such thing as waste, but wasted money. If I could see a gain to it I would agree. I will say this about "general rule" Its always a starting point but over time it usually becomes obsolete depending on the application. BB plywood is 99% bowed from delivery. Rarely find a perfectly flat sheet.

[Frank Drew]

Jack

Well, now you're changing the subject.

But maybe you're right about BB as it arrives so the solution might be to apply veneer to the convex side and let it bow back into flatness :D.

[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.....

[Mike Henderson]

All we use is contact adhesive for veneers in commercial unless the prints call for something else....
For furniture that's expected to last a century or so, and for non-backed veneer (also called raw veneer), I would not use contact cement. I'd probably use urea formaldehyde glue.

I've talked with quite a few professional furniture makers who use veneer and all of them have recommended against contact cement for raw (non-backed) veneer for furniture pieces.

I can't comment on commercial furniture or built-ins.

Mike

[jack duren]

We use backed or wood on wood veneers. All veneers purchased have tec specs as guide lines. Follow the guide lines. We usually use FORMWOOD veneers.

[Rick Christopherson]

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. David, When you say it like that, you are in effect telling people like myself and others that we don't know how to veneer. You don't do $50,000 kitchens or $15,000 tables on a mere wing and a prayer, and hope that they will stay together.

There are a lot of woodworking guidelines that get blindly repeated, but without understanding the basis behind the guideline, it is impossible to know when it is applicable and when it is not applicable. There is no such thing as a single steadfast rule that applies to all situations. Knowing when, is what separates the apprentice from the craftsman.

[Frank Drew]

Correct, I should have said specifically that contact cement isn't recommended for "unbacked, plain wood veneers".

[Peter Quinn]

This is the type of post that draws me to the Creek! Craftsman of vast and diverse experience weighing in on a technical issue somewhat central to the modern craft of wood working and not agreeing. Wonderful discussion here. Better than coffee.

I should preface my comments by noting that I am a mere journeyman and do not have vast practical experience with veneer, just a curious nature regarding its application.

It is my understanding that quality veneer is ALWAYS applied in EVEN numbers, the theory being that equal layers applied to opposing sides of a central core will maintain balance on both sides of that core. A quick look at any good plywood will indicate that veneer core material is always constructed of an ODD number of layers, which in effect equals a central, thin core layer balanced with even layers of veneer on each side. The core material is irrelevant, the force of wood movement must be balanced as best as possible to offer any hope of stability. This technology dates to the ancient Egyptians! Violate these rules and you are courting disaster, or worse, warping.

So by this logic the OP made his first mistake when laminating two pieces of veneer core plywood, as he has violated the balancing rule by not including a central core around which to form his new sandwich. Two pieces of veneer core plywood glued together without the inclusion of a single layer between them in effect creates a panel itself prone to warping. Right or wrong? He should have glued the two panels together with something between them.

Continuing this logic, the only chance he now has of rebalancing the tension in his panel is to veneer only one face of his laminated panel, thus creating an odd total number of layers. How he might calculate the thickness of this final veneer so as to reestablish equilibrium is well beyond me.

Another point reiterated by others is exactly what degree of flatness and stability is required of a free standing wall panel display? Sure, a panel which will be held captive in a frame such as a door which must meet other mill work evenly in a second plane and maintain even reveals has certain requirements for stability. But will a slightly warped decorative wall panel covered in figured veneer offend the eye of most observers, and can you even get close enough to the wall where it will be situated to establish a perspective for evaluating its flaws?

MPQ

[Earl Kelly]

David, I'm with you on this. I've glued up quite a bit of veneer, always raw and commercial cut. I've found the balancing veneer can be a different specie with complete success. The glue and grain direction is the most important factor for me.

Those that are trying to save a few pennies, should be looking for better sources of veneer. I have 1,000's of sqft of veneer that I paid less than $.25 sqft for. And when purchasing figured and exotics, can often find them for less than a $1 sqft. All the veneer co's have "backer" grade veneer.

All those using contact adhesive, congratulations with your success. I have seen a piece of furniture veneered with CC and it is still good today, 30yrs later. But, I've seen more, that were utter failures. Especially down here where the humidity gets in the 80-100% range with regularity.

Earl

[Jesse Cloud]

For what its worth, not an opinion, but some real data... I have had 3/4 baltic birch cup when using water based glue to veneer only one side.

[David DeCristoforo]

"David, When you say it like that, you are in effect telling people like myself and others that we don't know how to veneer...There is no such thing as a single steadfast rule..."

I don't mean to imply that you don't know how to veneer. And you are correct in that, in many situations (but not all) there are no hard and fast rules. But there are basic principals. For the most part, the basic principals are not myth. They are the result of many years of "research" by many different people working under many different conditions. All I'm saying is that it is not "good practice" to veneer only one side of a panel regardless of the thickness of that panel. But I am perfectly happy to acknowledge that there are exceptions to every rule, principal or concept. Let me ask you this... How many times have you bought 3/4" thick plywood that was not (with the exception of face quality) "balanced". Do you think that the manufacturers of sheet goods would continue to "waste" time and material veneering the "bad side" of sheet goods if there was no real reason to do so? I can assure you that, with profit margins in mind, they would not.

[Bob Wingard]

"How many times have you bought 3/4" thick plywood that was not (with the exception of face quality) "balanced". Do you think that the manufacturers of sheet goods would continue to "waste" time and material veneering the "bad side" of sheet goods if there was no real reason to do so? I can assure you that, with profit margins in mind, they would not."


Now c'mon .. let's get real with this. I'm sure a LOT of factors enter into the decision on the part of major manufacturers on how they are going to construct their plywood. One of which may very well be the "balance" you speak of .. BUT .. there is more than one kind of balance. They have the ability to use whatever number and thickness of plies they so choose, why not use an odd number of plies simply for aesthetics ?? Think about it .. how would your cherry or walnut bookcase look if the plywood carcase had grain running lengthwise on the outside, but inside the grain ran sideways ?? Not very appealing, huh ?? Now there's "balance" I could get concerned about.

If you're making a million sheets of plywood per week .. why not use an odd number of plies ?? Can't hurt, and might actually have some benefit .. .. beside, some of those crazy woodworkers might not buy it if they thought it wasn't made "correctly" by their way of thinking.

[Don Inghram]

Ok, here's another thought. How many of you would finish both sides of a project made from plywood. I know I always do. I think the same thing applies to finishing with veneer. Paint just one side of a piece of plywood and set it aside. Will it warp? Bet it does.

[Christof Grohs]

There are a lot of woodworking guidelines that get blindly repeated, but without understanding the basis behind the guideline, it is impossible to know when it is applicable and when it is not applicable. There is no such thing as a single steadfast rule that applies to all situations. Knowing when, is what separates the apprentice from the craftsman.

I suppose there are two ways of looking at this. The OP is, according to your definition, an "apprentice", if not he would not have posted this question. You (Rick) are, according to your definition, a "craftsman". You did not post here asking if you should back your panel. The question was posted by an "apprentice" who does not know "when". We (craftsman) can tell the "apprentice" what we feel is right or what is wrong based on our real life experience but as you said, "there is no such thing as a single steadfast rule..." I think each one of us must come to our own conclusion the hard way as to "when" enough is enough. However, I also think it is our responsibility as "craftsman" to encourage the "apprentice" to error on the safe side and gradually approach that fine line between what works and what does not, such that the "hard way" hurts as little as possible. No one is right or wrong in this thread, just food for thought.

[Rick Christopherson]

The OP is, according to your definition, an "apprentice"......I wasn't referring to the OP. I was referring to the number of people in this thread that are repeating what they heard or read elsewhere without understanding the concepts behind it.

Always: Finish both sides, Stack and sticker lumber, Alternate grains, cope an inside corner, etc. Never: Make long cross-grain joints, use the rip fence and miter gauge together, climb-cut, etc.

Every single rule mentioned above has a foundation in fact, and every single rule above is no longer applicable in certain situations. Yet every single rule above has been stated and repeated at one time or another as though they were absolutes. The difference between someone that knows the basis for a rule and someone that simply repeats the rule, is that the expert knows when the rule applies and when it doesn't, even if he/she does not point out these facts at the time of the telling of the rule.

[David DeCristoforo]

".... The difference between someone that knows the basis for a rule and someone that simply repeats the rule, is that the expert knows when the rule applies and when it doesn't, even if he/she does not point out these facts at the time of the telling of the rule..."

Well... I guess that let's me out... But, before I go, I would like to ask if that is a rule? And if it is, would there be any exceptions to it?

[Dave Tinley]

Ok, here's another thought. How many of you would finish both sides of a project made from plywood. I know I always do. I think the same thing applies to finishing with veneer. Paint just one side of a piece of plywood and set it aside. Will it warp? Bet it does.


Don-
And how about prefinished plywood?? I use and know of other cabinet makers that like to use prefinished 1/2" plywood for drawers and interiors of cabinets.
Yet every sheet I have gotten has been finished on one side only, and none of them have been warped or cupped. IMHO, the "rule" or statement of fact in regards to applying a finish to both sides applies more so to solid lumber.

[Frank Drew]

j
I was referring to the number of people in this thread that are repeating what they heard or read elsewhere without understanding the concepts behind it.

You're making the same kind of unfounded assumptions about others that bothered you when you thought they were directed at you. And, quite honestly, most of the people I've known who were really expert at something didn't actually refer to themselves as "experts".

[Greg Robbins]

Do you not know who Rick is?! :cool:

j

You're making the same kind of unfounded assumptions about others that bothered you when you thought they were directed at you. And, quite honestly, most of the people I've known who were really expert at something didn't actually refer to themselves as "experts".

[jack duren]

Seems this went from veneering both sides to contact adhesive to plywood opinions. Two extra subjects being created to test knowledge and skill. Guess a few couldnt stay on the yellow brick road.

I asked a question one time on John Bridges tile forum. The tile professional answered the question and I argued the answer. His final answer was "Your gonna do what you want anyway".

So be it....

[Peter Quinn]

Don-
And how about prefinished plywood?? I use and know of other cabinet makers that like to use prefinished 1/2" plywood for drawers and interiors of cabinets.
Yet every sheet I have gotten has been finished on one side only, and none of them have been warped or cupped. IMHO, the "rule" or statement of fact in regards to applying a finish to both sides applies more so to solid lumber.

How do you know? Have you gone back to check with a straight edge? And why would you use prefinished with only one side finished for drawers when both faces show? Do you put the finished side in or out? Tricky no?

In reality I doubt honestly that plywood under normal interior conditions finished on one side only over such a short length would move enough to effect the function of a drawer slide, but I can show you some solid wood (poplar or maple) that would rip your slides off the box if you tried it. And the OP's question was regarding a MUCH LARGER piece of plywood. Do you doubt that plywood moves? Try moistening one side of a piece of 1/2" with a sponge and watch how it curls. Or that solid wood moves? Try painting only one side of a front door and see how that goes.

And for the couple bucks more per sheet I spend for maple ply prefinished both sides. I think it adds $5 per sheet from my supplier? Not necessary on carcasses in dry places but comforting for bathrooms and near dishwashers.

[Dave Tinley]

How do you know? Have you gone back to check with a straight edge? And why would you use prefinished with only one side finished for drawers when both faces show? Do you put the finished side in or out? Tricky no?

In reality I doubt honestly that plywood under normal interior conditions finished on one side only over such a short length would move enough to effect the function of a drawer slide, but I can show you some solid wood (poplar or maple) that would rip your slides off the box if you tried it. And the OP's question was regarding a MUCH LARGER piece of plywood. Do you doubt that plywood moves? Try moistening one side of a piece of 1/2" with a sponge and watch how it curls. Or that solid wood moves? Try painting only one side of a front door and see how that goes.

And for the couple bucks more per sheet I spend for maple ply prefinished both sides. I think it adds $5 per sheet from my supplier? Not necessary on carcasses in dry places but comforting for bathrooms and near dishwashers.

Peter-
Unfortunatly the suppliers in my area only carry 1/2" plywood that is prefinished on one side. I wish they carried it the other way. In regards to how it is utilized, I put the prefinished side, inside. It is a good selling point for kitchen and baths.
In regards to the OP's question, it was in regard to veneering both sides and not in regards to finishing both sides.
And I am not doubting your assertion to the effects of moisture on solid wood, but just to test your theroy about 1/2' plywood, I wet one side of a piece of china birch 4" x 22" x 1/2". When I left the shop an hour ago nothing had happened, I will check it again in the morning.

[David DeCristoforo]

"In regards to the OP's question, it was in regard to veneering both sides and not in regards to finishing both sides. "

The point. As to Flexner's article, his basic contention is that finishing both sides of a panel will not correct or ameliorate the effects of improper drying and manufacturing. This may be true. But his later statement that cupping occurs in panels veneered on one side only if a water based adhesive is used is, I'm sorry to have to say, completely incorrect. If anyone wants to test this out, just veneer one side of a panel with "raw" wood veneer using AR glue. I can almost promise it will warp. OK, maybe not so much if it's like an inch thick or made of steel. But a piece of 3/4 " ply? Chances are very good that warping will occur. At this point I feel compelled to point out that I have been a woodworker since I was 16 and I have been a professional woodworker for 35 years. I have also been a widely published woodworking author with at least as much "cachet" as Bob Flexner so it's not like I don't know what I'm talking about here.

[Ron Bontz]

My 2 cents worth. The external force applied is equal to the sum of the internal forces. A cheap "balance backer" is often available from the same laminate sources. I made the mistake of not putting the balance backer on 3 large router tables for a couple of months when I got busy. Well needless to say a costly mistake. Mine was on MDF but I have seen plywood warp as well despite being sealed on the back. These days I just take a little extra time and cost and "balance" both sides on whatever I am laminating. It's better than regretting it later. If this is more than 2 cents worth, just put the rest on my tab. I am sure it is high by now. Best wishes.:)

[Peter Quinn]

Peter-
Unfortunatly the suppliers in my area only carry 1/2" plywood that is prefinished on one side. I wish they carried it the other way. In regards to how it is utilized, I put the prefinished side, inside. It is a good selling point for kitchen and baths.
In regards to the OP's question, it was in regard to veneering both sides and not in regards to finishing both sides.
And I am not doubting your assertion to the effects of moisture on solid wood, but just to test your theroy about 1/2' plywood, I wet one side of a piece of china birch 4" x 22" x 1/2". When I left the shop an hour ago nothing had happened, I will check it again in the morning.

Sorry to hear you can't get the 2X prefinished. Winds up costing me $5/sheet more. I like it for backs in high humidity areas. Edge banding prefinished ply is no joy for me though. Makes sense putting the finish to the wear side.

I had a guy spray some 1/2" birch 4X8 sheets for me on a bathroom job. I told him to back prime the B face, he scratched his head, I said "paint the other side silly." He decided the other side was dusty, so he wiped it with a damp rag and stood the sheets against the wall to dry. They went a bit wanky. Not much fun fitting in a frame and panel system. Try wetting a bigger square. Mine usually move, you could almost do curved work with it.

I think the OP wrote of a 5X5 laminate of baltic birch to hang on a wall, and I figure that is going to experience movement if he treats each side differently, especially if he uses a water based glue one face only. I doubt the finish would matter much. Course if he's spraying one side how hard is it to spray the other?

[jack duren]

Plywood is going to move no matter how its faced, Hang it on a wall or lay it on a floor its going to do its thing...I just hope its not hanging on the wall that gets the afternoon sun;)

[Homer Faucett]

"In regards to the OP's question, it was in regard to veneering both sides and not in regards to finishing both sides. "

The point. As to Flexner's article, his basic contention is that finishing both sides of a panel will not correct or ameliorate the effects of improper drying and manufacturing. This may be true. But his later statement that cupping occurs in panels veneered on one side only if a water based adhesive is used is, I'm sorry to have to say, completely incorrect. If anyone wants to test this out, just veneer one side of a panel with "raw" wood veneer using AR glue. I can almost promise it will warp. OK, maybe not so much if it's like an inch thick or made of steel. But a piece of 3/4 " ply? Chances are very good that warping will occur. At this point I feel compelled to point out that I have been a woodworker since I was 16 and I have been a professional woodworker for 35 years. I have also been a widely published woodworking author with at least as much "cachet" as Bob Flexner so it's not like I don't know what I'm talking about here.

I am not a professional woodworker, and have not been woodworking forever, but I had read many times about the need for using a backer when veneering with raw veneers, and wanted to see the actual effects of veneering without using a counterbalance sheet (which I'll call a "backer"). As this thread has pointed out, there are many passionate responses on either side, and I just wanted to decide for myself when I could "get away with" not backing a substrate. So, I took David's challenge myself, and here was what I got.

I took a piece of 1/4" birch ply that is about 18" x 24", and placed a nice piece of maple burl on it using Better Bond veneer glue and a vacuum press as one of my first glue-ups. I also made several smaller glue-ups on 1/4" plywood using some tiger anigre cut-offs. I did this for a few reasons: (1) to see how much glue needed to be used (I had heard that using too much would cause "bleed through"; and (2) to see whether a backer would be necessary if, say, panels were floated in frame and panel construction.

I glued these up last September, and set them in my unheated barn over the winter to give them plenty of adverse moisture changes. I will post a picture of the outcome and let everyone make their own conclusions, but I would agree with David that if you have a question about whether a backer is necessary, try it out and set it aside for a while if you have the time.

For me, it proved that if there was any warping whatsoever that could be attributed to imbalanced veneers, it was small enough that it would not be an issue in most case work or work that was supported by a frame. However, if I were making cabinet doors just out of ply without a frame, I might be concerned enough to add a backer. As has been pointed out, plywood can bow on its own without the use of veneer, so good design and construction techniques have to be followed regardless.

Just my observations and where I came out when I did my own test.

Good luck.