Woodworker's Journal 2011-35-Winter, страница 70

Beeswax, often sold and used as a solid block of wax, is a very green finish. Even mixed paste waxes are fairly green, usually containing limited amounts of VOC solvents.

Pros and Cons

Although water-based coatings are lower in VOCs, clear water-based finishes are also a bit weaker. For instance, water-based polyurethane has about the same abrasion resistance as oil-based, but it has lower solvent, chemical and heat resistance. One could make the argument that if the finish does not hold up as long and you must refinish more often, the extra

solvent involved in early refinish-ing offsets any savings you made initially. Of course, refinishing also means more time and money spent. But there is a way around that. More and more, single-component, self-curing water-based coatings are being offered to kitchen cabinetmakers, and they match oil-based polyurethanes in durability. They've long been offered as floor finishes and are slowly becoming more popular for furniture as well.

While water-based coatings are generally considered greener, there are aspects to them that make them less green, at least in some minds. The resins used in water-based coatings are typically synthesized from petroleum, a nonrenewable resource that has a fairly high carbon footprint, thanks to the energy needed to extract and ship it. By contrast, the resins in oil-based varnish and polyurethane are made from modified linseed, tung or soy oil, all renewable-source plant oils grown right here in the U.S. The tradeoff is natural, renewable, local resins with a higher dose of VOC solvents versus synthetic,

foreign imported petroleum-derived resins with a lower dose of VOC solvents. As I said, this is not an easy equation.

Oil-Based Coatings

Danish oil, teak oil, spar varnish and the whole field of oil-based varnishes and polyurethanes, both liquid and gel, make up the next category. In general, these finishes are relatively safer for us than for the environment. They contain ozone-generating VOC solvents, and thus are not good for the environment. However, the ones they contain, such as mineral spirits, are fairly safe for us, at least in the limited amounts to which we are exposed. Their high solids content, often 45% or so, means what solvents they do contain are in more limited amounts than what you would find in lacquer, for example.

Although the solvents are petroleum-based, the resin portion is made from natural seed oils, usually linseed, soya or tung. Such oils are renewable crops grown here in the U.S., and they require little processing to go from raw oil to resin. What's better is that

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*J

Does My Going Green Really Matter?,

If you are not part of the problem, nothing you do differently will make you part of the solution.* ','J

___? As far as finishing materials are concerned, most of you are not part of the problem. Most hobby

woodworkers go through less than 10 gallons of finish per year. At that rate, switching to wate£base?l^ finish from solvent or oil-based would be akin to someone who drives only one mile per week tradinc his or her car for a hybrid. It's silly and arguably counterproductive as well. The reality of the situation is that, compared to the big ozone-producing generators, which include our cars, the electricity we use and the agriculture that provides our food, finishing amounts to small potatoes ' % indeed. Some years ago, I was at a meeting of finish chemists being addressed by an EPA repr&entative.on the subject of limiting ozone generation from VOCs in coatings. Upon being challenged, the representative admitted that the solvents in clear wood coatings account for less than one percent of the country's total ozone generation problem. In other words, if all wood finishing stopped tomorrow completely, the improvement would barely be measurable and might fall well within ariormal margin of error. With that in mind, it makes little sense for most of us to buy fancy equipment or to through a long learning curve just for the sake of using lower VOC materials. We're far beVter of&idoptT^ig green finishing techniques than switching to greener finishes. That strategy not only prevents waste, thus helping our carbon footprint, but saves us money to boot — and in this economy, that's nothincufl^neeze at.