Woodworker's Journal 2009-33-5, страница 66

Finishing Hotline

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.

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 these coatings are almost never sprayed, but rather are applied either by brush, or by wiping on and off, as in the case of Danish oils and gel polyurethanes. Those application methods have a very high transfer efficiency (see "Waste Not, Want Not" below right), which means very little is wasted and only a minimum of solvent is used.

Traditional Lacquer, Etc.

Traditional lacquer contains lots of VOCs and HAPs, some of which are not only strong ozone generators but are harmful to humans as well. These solvents are also usually quite flammable, providing yet another safety issue. What is worse is that they are typically formulated for spraying, a very wasteful application process that not only wastes coating, but also uses up a lot more solvent in both thinning and cleanup. Catalyzed lacquer, conversion varnish and pre-cat lacquer have all of the above disadvantages and may contain formaldehyde and hazardous acids as well. For that reason, these coatings are considered the least green option.

Steps Toward Green Finishing

I promised you that there is an easier, cheaper alternative that lets you use nearly any finish and still come out greener. It's called green finishing. The good news is that by slightly changing the way you use finishes, you can be greener and save money to boot. Green finishing employs two means to lower VOCs: reducing waste, often through low-tech application, and recycling solvents.

Waste Not, Want Not

The first step in reducing waste is to buy wisely. In other words, try to buy only the amount of finish you need for the job. Too often, leftover finish ends up crusting over or otherwise going bad and gets thrown away. That does neither the environment nor your pocketbook any favors.

A less obvious way to reduce waste is to choose an application method with a high transfer efficiency. Transfer efficiency is the percentage of the finish you buy that actually ends up on the wood. Most standard spray guns have about a 25% transfer efficiency, meaning about 75% of the finish gets wasted, mostly blown out through the spray booth fan or

Finishing continues on page 68...

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. 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 water-based finish from solvent or oil-based would be akin to someone who drives only one mile per week trading in 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 representative 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 a normal margin of error.

With that in mind, it makes litde sense for most of us to buy fancy equipment or go through a long learning curve just for the sake of using lowerVOC materials. We're far better off adopting 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 nothing to sneeze at.

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