You can use any finish, sanding sealer or paint under the glaze. You can sand this first coat if you want. But sand lightly with fine sandpaper so you don’t sand through, or the glaze will become a stain and color the wood. Sanding or steel wooling has the
benefit of roughening the surface so the glaze can bond better to it.
You can stain the wood under the sealed surface, leave the wood unstained or fill the pores of the wood. But in all cases, you should apply the glaze close enough to the wood so you can still apply one or more topcoats of finish to protect the glaze from being rubbed or scratched off without getting the overall finish build too thick.
Because there’s no build with oil finishes or wax, you can’t glaze successfully between coats of these finishes. You must use one of the film-building finishes.
To apply glaze, wipe, brush or spray an even coat onto the surface. Then manipulate the glaze with the following methods.
• Wipe off the unwanted glaze while it’s still wet. In most cases, this means wiping the glaze off raised surface areas and leaving it in recesses on carvings, turnings, mouldings and raised panels. But it can also mean wiping off flat surfaces in a way that imitates grain or other decorative effects.
• Wipe off the unwanted glaze right after the thinner has flashed off and the glaze has become dull. This is the same as wiping off while still wet, but the glaze is usually a little easier to control at this point.
• Using fine steel wool, abrade off the unwanted glaze after it has dried. There is a risk that you might abrade through to the wood, but it’s nice to know that you can always use steel wool to remove glaze if you don’t get enough off with a cloth before the glaze gets too hard.
• Using an almost dry brush, spread the glaze out thin to achieve the appearance you want. All this amounts to is continuing to remove glaze with a brush you keep fairly dry by wiping with a clean cloth until you achieve the effect you want.
• Adjust the color of the object you’re finishing by brushing glaze out thinly and evenly over the surface. As long as you keep the glaze thin, you won’t muddy the wood much. This is an excellent technique for creating a more perfect color match.
• Using tools such as rags, sponges, brushes, grainers and toothbrushes (to create a spatter effect), create a decorative faux pattern. Here, the techniques and colored patterns you can achieve are endless. Many books explain these techniques. Most are focused, however, on decorating walls rather than woodwork.
• Instead of manipulating glaze you’ve already applied, use a “dry” brush to apply the glaze to raised areas of carvings or turnings, or to flat surfaces to create the appearance of dirt accumulation. Begin with a totally dry brush and swirl it in some thick oil or Japan color you’ve applied to paper, cardboard or wood so that some of the color is transferred to the bristles without making them wet. Then brush lightly.
Most glazing problems occur because you’ve applied the glaze too thick or not allowed it to cure enough before applying the topcoat of finish. The two are related because a thick layer of glaze takes significantly longer to cure.
Too thick a layer of glaze (most common in crevices and recesses) weakens the bond of the finish to the wood because the glaze layer itself is not strong. The finish applied on top of the glaze could separate if knocked or abraded and this would pull some of the glaze with it and leave some attached to the surface underneath. This problem is even more likely to occur if the glaze hasn’t thoroughly cured.
Not allowing the glaze to thoroughly cure can also lead to the topcoat wrinkling or cracking. If this happens, you’ll have to strip the finish and start over. PW
Bob is the author of “Understanding Wood Finishing” and a contributing editor to Popular Woodworking.