"Superficially valuable or pleasing appearance."
Synonyms listed for veneer include: façade, front, show, mask, guise.
The part I article deals with the reasons which Adam feels justify the use of veneer, while part II (found in the following issue, #186) deals with the 'how' of veneering. I suggest readers who have not had a chance to read the part I article do so by clicking the provided link before continuing on with my commentary. You see, while I respect the author's opinions, I have a diametrically-opposed view on veneer, and I would like to take the opportunity here, for whatever it is worth, to serve up a few counterpoints to the opinions brought forth in the above-cited articles.
"...technology has improved. Core materials have improved tremendously, including the introduction of MDF. Space-age glues and vacuum technology have simplified the pressing process".
He's absolutely right, though I'm not so sure that plywood, a common substrate upon which veneer is glued, has improved. While plywood is indeed a wonder material in many respects, with some outstanding qualities (I use it to make storage boxes for my portable power tools), today's plywoods are getting cheaper and lower in quality than they used to be, with fewer laminae, from what I have observed. 'Good' plywood, when you can obtain it, is certainly not cheap. And MDF , essentially ground up sawdust bound together in a sheet with adhesives, is a very flat and uniform material - ideal, I would say, for making woodworking jigs. But not furniture. It has poor strength and if is gets damp, a disaster unfolds.
Adams notes that 'correctly balanced' veneered plywood panels is "far stronger than solid wood of the same thickness." This is true, but only in a limited sense, and depends upon how one defines strength. Solid wood is anisotropic, having different degrees of strength relative to the direction of load in respect to the run of the grain.
In a piece of plywood, each laminae has the grain running crosswise to the layer above and below it. In order to keep the plywood stable, there are typically an uneven number of layer of layers, so that the outermost layers both have grain running the same direction. In short, a little less than half of the layers in a sheet of ply are running crosswise to the layer one sees on the faces. This means that plywood is stiffer in resistance to bending in one direction than another. And when compared to a piece of solid wood of the same species (typically, that is, a softwood) as found in the plywood sheet, one can see that all of the grain in the stick of wood will be running the same direction. If one measures strength then by resistance to bending, a rather important matter in most furniture construction, then solid wood is a better and stronger choice. In short, plywood is not often a good choice to resist bending because the plies with cross grain contribute almost nothing to resist the bending load that a shelf, say, must withstand. Plywood bookshelves are ubiquitous these days, and over time they tend to sag - possibly this is due to creep in the adhesive. Certainly, plywood is not an ideal choice for that application, but it is cheap.
Plywood is very strong in other respects compared to solid wood, like shear parallel or perpendicular to 'grain' direction of loading, but I would say that those issues are generally minor concerns in furniture. Resistance to bending is much more important.
There's an online calculator (<-- link) available for determining the sag of various shelving materials, and I invite you to take a gander. Comparing apples to apples, I input data for a 3/4" Fir Plywood shelf, 36" long and 10" wide, with either a balanced load or an unbalanced load, and compared the resulting deflection to solid 3/4" Douglas Fir (coastal) - the plywood deflection was 50% greater than the solid wood. A common way to stiffen up a plywood shelf? Adding a solid wood edging.
More to the point though is that if I wanted to build a stiffer shelf, in plywood I am left with laminating more plywood layers together, to build up, say, a 1.5" thick shelf from two 3/4" sheets, or constructing a torsion box arrangement using thinner plywood; both are solutions which result in a thick wooden shelf and that takes away from the available storage space in the unit and suffers an aesthetic penalty in many instances. Of course, I could also apply metal angle iron reinforcement and so forth as well, but that is a proof positive that plywood is insufficient to the task. In solid wood, if I need stiffer shelves I simply move to a species which is inherently stiffer, like Oak, Maple, Goncalo Alves, Purpleheart, etc..
Sag is of course an issue with solid wood as well. I have an inexpensive bookcase (on loan from my mother in law) in my living room about 36" wide made of 3/4" Pine, and the shelves sag slightly from the books. Pine shelves and a 36" span do not combine especially well - if it were 18" or 24" wide, then things would probably be fine. When I made myself a bookcase, 30" wide, I made the shelves out of cherry and there is zero sag when loaded with books. With plywood you don't have that option of changing materials (though there are pricey 'aircraft' plywoods which are stiffer), as the interior constituents of plywood are often not especially different from one another. You can get more layers or fewer, but all of the layers are still generally a softwood - or worse. One cannot readily obtain, say, 3/4" plywood in which any/all the interior laminae are composed of a stiffer wood, like Maple or Oak. When you buy 'oak' or 'maple' plywood, the only place the oak or maple is found is on the wafer thin exterior faces. It's really a softwood ply.
Now of course, while I can readily switch from a fir/pine bookshelf to a bookshelf made from a stiffer wood, there is often a price penalty to be incurred for that. But at least you know what you're getting. With the veneered plywood shelf, one could pay vastly greater sums for having East Indian Rosewood veneered shelves, but underneath it all, you still have the same fundamental reality - it's a plywood shelf. It's not going to perform significantly better than the fir-faced plywood shelf.
Adams asserts in his article, in a section entitled, Why Veneer Survives - and Thrives, that veneers are,
"...as a material, green by design - it's durable, renewable, and sustainable."
I was somewhat astonished to read that, however I thought I would read on to see how he comes to this conclusion. Well, he doesn't really back those statements up, however I can surmise that a part of this boils down to the apparent economics - you get more yield of veneer from a given stick of wood, in terms of square footage that can be covered, than you do when sawing boards out of that same log. The argument for economy in other words. Economy of materials is 'efficient' and leads to a less expensive product while multiplying the profit ($$$) one can obtain from a given log. Perhaps that best explains why veneer thrives these days, the good old profit motive?
There's a slight problem though with the economy argument however, and a problem which directly affects the 'green' picture and the 'sustainability' of veneer. I'll look that matter in the next post.
Thanks for dropping by the Carpentry Way today.