Foundational Finish Facts: A Case For Broken Corners

Proper surface preparation leads to a perfect finish every time.The foundation of any good finish is proper surface prep. One of the key elements of that preparation is breaking all the sharp edges. I know it sounds fairly obvious, but lots of woodworkers skip right over it and ruin their projects.

I get it, you’ve spent days, week or even months working on your latest project. Agonized over every detail. All that’s left is the final surface prep (plane, scrap or sand) and it’s ready for finish. You hate this part, but you go through the motions and get it done. Apply color and a sealer coat, and it ends up with a hide that’s courser than a porcupine. You grab super fine sandpaper and begin knocking down the finish and end up with blonde highlights everywhere.

Broken Corners

Water beads on the hood of a car are caused by surface tension.

There are lots of reasons to soften the edges of your pieces. Many people think it’s done solely for hand-feel purposes. But there’s a very scientific reason for broken corners.

Have you ever washed and waxed a car (or seen a car wax commercial)? What happens when water is sprayed on the car? It beads up, right? That’s caused by surface tension.

Spray the water on, most of it sloughs off, but the remainder beads up because the water drags on the paint surface. You ask, “How does this relate to my white striped furniture?” The same principle is at work.

If your piece has sharp edges, the finish can’t flow over the surface uniformly. It reaches the edge of a face and tension builds causing it to bead, but not necessarily into individual droplets.

The tension stops the flow of the finish around the sharp corner leaving almost no topcoat on the sharp edge. When you use sandpaper to knock off the nibs, you sand right through the color and the clear, protective layer.

By breaking, or softening the edges on your pieces, you allow the finish to flow over the rounded surface similarly to how it flows across the other surfaces. Softened corners leave a thicker layer of clear coat that’s tougher to sand through. So, break your corners, it feels and looks better.

If you’d like to learn more about finishing, use the coupon code day2 (good through Christmas Day) at checkout when signing up for my 2019 Finishing Week class. You’ll get a 10% discount and a whole lot of finishing knowledge.

Softening the corner allows more finish to flow over and protect the corner from rub through.

Sharp corners leave less finish because of surface tension.








— Chuck






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