With the ever-more strict regulation of wood finishes containing VOCs (volatile organic compounds) and a general increase in consciousness of health and environmental issues, more and more woodworkers are doing something they never thought they’d do: making the switch to waterborne wood finishes. In this article, we’ll take a look at how far waterborne finishes have come in recent years, and what makes them a viable choice for just about any woodworking project. We’ll also offer a couple of tips on applying waterbornes, and point out a couple of top picks.
Waterborne Finish Basics
Finishes that clean up with water are often referred to as “water-based”, which is a little misleading. From a technical standpoint, “waterborne” is a much more fitting term. In fact, the term “water-based” itself has been a hindrance to the reputation of many finishing products over the years. And understandably so: If a finish were truly water-based it would wash off with a wet rag no matter how long you let it dry, and wouldn’t be much good for anything. But in reality, water plays only a supporting role in the process that turns waterborne finish from a liquid into a durable protective film.
Understanding how a finish that cleans up in water can can adequately protect a wood surface is easier when you know a little about how the chemical process works. A waterborne finish is composed of minute spheres of resin (most commonly acrylic and polyurethane) suspended in water along with a slow evaporating solvent, such as glycol ether. When you spread a waterborne finish out in the open air, the water begins to evaporate. The solvent, which evaporates slower, stays behind and softens the protective coating on the tiny resin latexes, causing them to bond into one continuous film. Since the solvent is the active ingredient the curing process, and not the water, the protective coating that results is not affected by moisture, and often has considerable resistance to a variety of other substances.
Article – Copyright ©2009, Rockler Companies, Inc.
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