Woodworking can be a science project

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Woodworking can be a science project
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Some years ago, I was discussing “higher” education with a friend, who humorously observed that “Any subject with the word ‘science’ in it probably isn’t.” The more I thought about it, the more I realized it was true. Think about it: political “science,” behavioral “science,” environmental “science” …

On the other hand, there are a multitude of areas in life — especially in the arts and crafts — where activities and functions, and success or failure, are determined in great part by the understanding of science, even if you don’t think about it explicitly.

I remember once engaging a self righteous “academic” who believed that wood finishers were essentially glorified ditch diggers, that we employed no real science or technology in our work. After presenting him with the following, the conversation suddenly ceased to be a conversation. I was on my own with a soliloquy at that point.

So, if you ever get the temptation to either think that because you are a finisher you are some sort of Cro-Magnon, or have an insufferable in-law who is embarrassed by what you do and possesses the dim-wittedness implied by it, toss this little piece their way.

The practice of furniture finishing and restoration requires the practical application of many technical and scientific disciplines. To competently complete his task, the artisan must be learned in physics, chemistry, materials science, biology and physiology in each project. For the most part, practitioners are too busy getting the job done to truly reflect on the technological sophistication of their projects, so I’d like to point out some of these truths.

Chemistry
The applications of chemistry to finishing are nearly endless.

Organic chemistry leads us to polymer chemistry, which in turn is generally dependent on the nature of the physical chemistry and thermodynamics and reaction rates. (I think I hear eyeballs rolling back in their heads right about now.) The chemistry of resins is all about polymer chemistry. How hard or soft is the finish? How tough or brittle? How transparent? The saturation of the surface is almost entirely dependant on the molecular weight of the resin, which is why a hand-rubbed shellac finish (very low molecular weight) looks absolutely delectable, while a sprayed epoxy or polyester finish (very high molecular weight) has a very “plastic” appearance.

Even the delivery method and formation of the finish film are dependent on the chemistry of the materials. The more you understand this, the greater your predictive success at the workbench when you need to tweak the process. Solvent interaction and effects on coatings performance is one of my own great interests, as it expands my options immeasurably when it comes to manipulating and using coatings systems on a near-daily basis. How well something is dissolved by something else, and how rapidly it occurs or is reversed, is a purely chemical question for the most part.

Physics
Much depends on optics and visual perception (see physiology below). In order for the human eye to perceive color — and perceive it correctly — there must first be a light source. The nature and color spectrum of that light source makes all the difference to the finisher “getting it right.” In principle, you can get close results in almost any lighting system, but for the best results you should do all your finishing work with lighting that mimics that of the furniture’s final location. Otherwise you might be a victim of phenomena known as “color constancy” or “metamerism.” An example of this is when you do final color matching late at night under cheap fluorescent lights, but by the light of morning you didn’t get close.

In fact, every aspect of appearance can be traced to the physics of the materials. As I mentioned before, the molecular weight of a polymer affects the nature of the light absorbed, transmitted, or refracted (bent) by that material. In addition, the ability of a coating to reflect light determines the gloss. If light is left organized in its reflection, we define that as high gloss. If the light is scattered by either the topography of the surface or by light-scattering particles just below the surface, we get matte finishes.