Expert's Corner — water-based

Whenever water or any stain or finish that contains water comes in contact with wood, it causes the wood fibers to swell, which is called “grain raising” or “raised grain.” After the water has dried the wood feels rough to the touch, and thinly applied finishes also feel rough. Raised grain occurs no matter how fine you sand the wood before wetting it. Because you can’t prevent raised grain if you use a water-based product, you need to deal with it so the final finish comes out smooth. There are two methods: The first is to raise the grain and...

As with all finishes, you should always sand the first coat of water-based finish smooth because it always dries rough to the touch. It’s also the best policy to sand additional coats smooth after they dry to remove dust nibs and other flaws, until the last coat, which you can leave as is.Water-based finishes dry rapidly, almost as fast as the water evaporates from the finish. So the drying occurs quicker on hot or dry days and slower on cold or humid days. How do you know when the finish is dry? It powders on the sandpaper and on the...

Finishes differ in the amount of color they add to wood. Though you may not notice much of a difference if you are applying the finish over a stain, there is a significant difference when no stain or other coloring steps are used. In the accompanying picture, you can see the differences clearly. On the far left is paste wax. It adds almost no coloring to the walnut. Next is water-based finish, which also doesn’t add color, but it does darken the wood a little because of the penetration. In the middle is nitrocellulose lacquer, which adds a slight yellowing...

There are two critical elements that make for a great finish - selecting the right brush, and using the right technique. Practice counts as well. You don't expect to cut perfect dovetails the first time round, nor should you expect to achieve a perfect finish without practicing your finishing technique. I frequently choose brushing because I have a small shop and brush clean-up is fairly quick. Most of my finishing is done with shellac or varnish. Occasionally I'll use a water-based finish for light-coloured woods when I want a super clear finish. However, I've never used lacquer, so my comments...

When sanding wood in preparation for a stain or finish, you need to remove all the problems in the  wood – mill marks, tear outs, gouges, etc. – with the coarsest grit sandpaper you’re using before  moving on to finer grits (to remove the coarse-grit scratches). This means that the coarse-grit  sandpaper you begin with should be able to remove the problems quickly and efficiently to reduce  the amount of work required. On the other hand, with factory pre-sanded veneered plywood or mdf, beginning with 150-grit sandpaper is usually adequate.As an example, 100- or 120-grit sandpaper is usually coarse enough...