How a finish will stand up to use isn’t the only consideration, of course. The finish should be reasonably easy to apply, and most importantly should look good when it dries. There is a wide range in the appearance and ease of application among currently available products, and unfortunately, the failings of a few have generated a couple of common misconceptions. The first says that waterborne finishes are all but impossible to spray on. The truth is, many waterborne finishes spray exceptionally well. In fact, certain waterborne finishes have to be sprayed on for acceptable results.
The second misconception holds that waterborne finishes all have a hazy, bluish appearance when dry, and therefore aren’t a good choice for darker colored woods. Here again, it really depends on the finish. In reality, most waterborne finishes dry almost perfectly clear. What’s missing, for most woodworkers, is the amber tint that they’re used to getting from all oil-based “clear” finishes. In other words, most people have come to associate the rich, amber color that most oil finishes add to the natural color of wood with the “correct” result.
Looked at another way, waterborne finishes actually have an advantage over traditional oil-based finishes: They give you more control over the final appearance of your projects. In some situations – when you want to maintain the color of light colored woods, for example - the best appearance a finish can provide is none at all. In other words, the finish should be perfectly clear, and a waterborne will get you closer than anything else. In other situations, where the familiar amber color of an oil finish is a benefit, you have a couple of options: Most waterborne finishes can be tinted to the desired color. Better still, you can use Rockler’s WunderCote. WunderCote is an easy to apply wipe on waterborne finish that comes pre-tinted to emulate the color of a light amber oil-based finish.
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.