Woodworker's Journal 2011-35-Winter, страница 71
Green Application k f jyd When it comes I (f 1 to being environmentally responsible, how you apply a finish can be 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), 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 fin ish 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 trapped on the filters. Even those systems that boast higher transfer efficiency, such as HVLP turbine rigs, only reach about 65% transfer efficiency. That's still a lot of waste. Compare that with a wipe-on gel polyurethane. If you're like me, you apply it with a piece of nylon abrasive pad. One pad will do an entire roomful of furniture without wearing out, and when you are all done, very little remains on the pad to be dried out and thrown away. The waste comes only in how much you wipe off, and with attention, you can keep that to a minimum as well. Since applicators and wiping rags are allowed to dry out, then get thrown away, there is no solvent used for cleanup. Using a brush to apply finish approaches near 100% transfer efficiency. The only amount of finish that does not make it onto the wood is the tiny bit you must clean out of the brush bristles when you are all done. As for the cleaning solvent, that can be kept to a minimum through recycling. Recycling Solvents That brings us to the other way we can be greener no matter what finish and solvent we use. Solvents may not be forever, like diamonds, but they are reusable again and again. The mineral spirits you use to clean your brush or the lacquer thinner you use to clean spray guns can be poured into a lidded container and shelved. Over time, the heavier foreign matter will settle to the bottom. When that happens, decant the clearer liquid atop and reuse it for cleaning the next brush or gun. You will lose some each time to evaporation, but you will be surprised at how much you can reduce your VOC consumption by recycling your cleaning solvents. By now it should be obvious that by avoiding waste and recycling solvents, you not only reduce your carbon footprint on the earth, but also save money in your wallet. After all, if you are buying fewer cans of finish and solvent, you are coming out ahead in every way. WINTER 2011 71 |
