What you coat a carving with has distinct practical and esthetic consequences. I tended to make things for boats; quarterboards, billet heads, eagles, or transom banners. I always used carefully applied varnish, paint, and gold leaf. Polyurethane varnishes were unreliable for adhesion and tended to peel away, so I stuck with the older fashioned spar and marine varnishes.* It was a pragmatic decision.
A quarterboard almost always received up to seven coats coats of varnish; a finish failure was a costly error. But, once you learn to prepare a surface for varnish properly and apply the coats evenly and thinly, it’s an easy finish to use. So don’t slop it on, and don’t over brush it.
The instructions for most varnishes call for applying later coats within twenty-four hours. The can will say something on the line of “…allow to dry for twenty-four hours before recoating.” That’s confusing because the varnish film may technically be “dry” but not completely cured. It’s that incomplete curing that allows for adhesion between coats. Wait over twenty-four hours, and the instructions will frequently advise a light sanding. The sanding roughens the surface enough to aid bonding.
A trick I learned from a professional varnisher was to coat with three thinned coats, twenty-four hours between coats, and only then lightly sand. On open-pored woods like Mahogany, this worked well. After those first three coats and sanding, you began to build the surface with full-thickness coats of varnish and sanding lightly between coats.
You may be saying, “seven coats of varnish! That’s thick!” Bear in mind that a marine environment is very harsh on wood. Don’t protect it, and watch it deteriorate rapidly. You may also be thinking about just dipping the finish from the can and smearing it. I’m not being facetious when I say that if I saw you doing that in a boatyard, you’d get fired that day. The idea is to build a lovely finish, coat by coat. No single coat is very heavy.
Since we are dealing with carved wood here, you need to avoid varnishing so heavily that the finish pools in the carving. I like to use a good quality varnish brush or a nice foam brush to ensure that my letters are coated but not filled.
If a carving needs to be gilded, the gold leaf gets applied after the finish. Gold leafing is not a topic for this post, but let me warn you that you don’t want to finish the varnish cycle one day and start gilding the next. Remember what I said about finish adhesion. The day after you finish, the surface has just begun to cure. Put the gold leaf on right away, and it will not only go on where you want it but everywhere else too. Cure in a warm room for a week ( not a cold shop).
Finishing brightwork is an art. The idea is to create a protective finish against a very harsh environment and have one that you are proud to flaunt.
This post is only a brief probe into varnishing—a foray. I haven’t addressed “lace curtains” and “holidays” yet. If you are interested, there are several excellent books on brightwork; I tend to like Rebecca Wittman’s Brightwork: the art of finishing wood.
*Please note that the manufacturers of marine finishes have conquered many technical issues with polyurethanes in recent years.