In my last article, I stated at the end that I had written a little over 1000 words and that after doing so I felt as though I was writing an argument in favor of using water-borne finishes. For those of you who read “Gluing Joints: It's A Surface Thing,” the thrust was, contrary to the title, how moisture affects wood as well as wood finishing.
I referenced an article by Gene Wengert entitled “Gluing tips: How to make strong joints.” Gene’s writing focuses on how moisture content can affect the beginning of a project (milling and glue-up) as opposed to mine which tries to tie the moisture-in-the-air-affects-wood issue all the way to the end when the finish is applied.
Gene Wengert, aka The Wood Doctor, troubleshoots wood related problems, and explores lumber and veneer
Moisture in the air affects wood to some degree forever. Since my job is to write about wood finishing, I felt that Gene’s article shed some light for us regarding the need to build, sand, and get the project finished as soon as possible so that we could have the best surface adhesion from our finishes. Specifically, the point I was making was that allowing the project to sit unfinished, especially after final finish sanding is completed, can cause problems.
After having read the article in publication, it also occurred to me that some readers may have missed the fact…and I didn’t specifically say one way or another, that article was specifically directed toward non-water-borne finishes.
Switching now to the subject of water-based stains, dyes, and coatings, one finds that so doing creates a whole different set of parameters. From here on, I will be discussing applying water to the wood’s surface in the course of the finishing process. In some instances, that can amount to quite a bit of water.
Water and wood are not always good friends. That is especially true when it gets to the end of the build and you want to seal things up. But 21st century water-borne technology has come a long ways. At the expense of going into things that I don’t want to cover here, let me refresh your mind with a bullet list of common water-borne misconceptions. Most of these I do not intend to cover here.
Water Borne Coatings
Most folks agree that those are the most common complaints heard when we talk about water-borne coatings. They are not all true.
Let’s just talk about the first bullet as it is most relevant to this discussion. Yes, water raises the grain. We all know that and we are constantly reminded of that in print articles on the subject of water-borne coating application.
I find it somewhat of a tempest in a tea pot. I have used water-borne dyes, wipe stains, clears, and pigmented coatings and, at the end of the day, I don’t see that nor do I do anything different in my prep for these finishes that I would otherwise do with solvent-borne coatings.
What perfect timing. I just read yet another article in a major woodworking magazine where the finish of choice was a water-borne brush-grade clear. The writer stated that he deliberately wet the wood before final sanding to raise the grain so that it would not do so upon application of the clear coat. Okay, that is not a bad idea. I’m sure it helped. It probably is more essential the closer to the wood that you want to be with your finish. But how much raise occurs and is it measurable? How much of it is repeatable? For example, can you sand, wet, sand, wet, sand, etc? I think not. Therefore, the raising is probably finite.
We use water to “bust the grain” or open it up so that stains may be applied more evenly or with greater color intensity. I just did a project and found a big dent in one board. I used the tried and true method of a wet cloth and a hot iron to steam out the dent. That’s REALLY busting some grain! But it only goes so far. I could iron and steam all day and that particular dent wasn’t going to disappear.
The changes from the point in time when finish sanding ends and finish is applied are finite but they are there. The wood’s surface cell structure will only react so much for so long to moisture. After that the effect plateaus and the wood’s surface is less reactive. Granted, the longer that the wood sits, the deeper into the wood’s cellular structure may be the effect and the more pronounced it may be. The point is that the wood’s surface will react to moisture in the air and the cells will move. In the process, the ability for the coating to find something to adhere to may change as well.
I think I may have been wrong. Water-borne coatings may only help adhesion so much for so long before the window of opportunity begins to close. So the whole point is, again, get the finish applied to freshly sanded wood while the window of opportunity is wide open and the wood has the most to give in accepting the finish…whatever it may be. Those last four words of the previous sentence apply equally to both solvent-based finishes and water-borne finishes.
Until next time…spray on!
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