The pros and cons of the two most common acoustic-guitar finishes.
As I write this, I’m on my third day of filling in for our vacationing finish man. Fill-in duty would normally fall to his supervisor, but he’s out sick, so here I am. Welcome to the world of small-business ownership! I actually started out in this business as a finish person at Stelling Banjo Works here in Virginia, so I have some experience in this part of the process. I also stay involved in an advisory capacity. But as we all know, advising and doing are two very different things.
Two things struck me today: First, these guys work very hard for us. And second, even though the materials have changed a little over the years, the basic process seems to be the same. The finish room is often the bottleneck in a shop like ours. This is due in large part to the intense manual-labor aspect of the work and the fickle nature of wood as a medium.
The great debate. I’ll do my best to explain a few differences between the two major types of guitar finishes while trying to avoid “the great debate” (whether nitrocellulose lacquer or catalyzed finishes are superior). In my opinion, there is no discernable difference in tone or volume between any of the available finishes. Other folks whose opinions I very much respect have different views here, but I can only speak of my experience. (Several other finishes are currently in use, including varnish and even shellac, but in the interest of space, I’ll stick to the two most common ones.)
Catalyzed finishes. The catalyzed finishes used by pros, such as the catalyzed urethane we use, are relatively impervious to the elements, with low freezing points. They’re also resistant to solvents your guitar may encounter, such as bug spray and suntan lotion. Catalyzed finishes also provide greater resistance to dents and scratches, and they’re environmentally friendly, with fewer volatile organic compounds and less general shrinkage.
On the other hand, catalyzed finishes are expensive. They’re harder to apply, and more difficult to touch up as needed.
Lacquer finishes. Most of the old guitars we all revere were finished with lacquer—and “respect for tradition” merits a check in the pro column. Lacquer is also relatively easy to use. (If you can handle a spray can from the hardware store, you can probably work with this stuff.) And compared to catalyzed finishes, lacquer is easy to sand and touch up.
Lacquer’s biggest negative is its high freezing point. If your lacquer-finished guitar is exposed to temperatures below 32 degrees for any length of time, the top’s finish is liable to crack or “craze” once the guitar is returned to a heated space. Some think this gives the guitar a cool played-in look, but it makes others want to jump off a building. Lacquer also has low resistance to solvents and sweat. We’ve all seen old guitars with dirty, sticky rings where the player’s arm has pressed against the top.
Care. For the most part, the two finishes require the same sort of care. You can usually clean them with a soft, damp cloth, followed by a softer dry one. It’s okay to use polish sometimes, but avoid ones that contain silicone, which tends to build up over time. (Most commercial guitar polishes have no silicone, but it’s worth checking.)
You can use naphtha on most finishes to remove stubborn dirt or other substances. (At least that’s true for urethanes and lacquers. If you have a different type of finish, or simply aren’t sure, it’s always a good idea to get the blessing of your builder.) Naphtha, a mild cleaning solvent, is available in most hardware stores. But do not—I repeat do not—confuse naphtha and acetone! The two might reside next to each other on the hardware store shelf, but acetone melts most finishes.
One last note: The notion that you can polish a matte-finished guitar to a shine like a buffed-finished guitar is a misconception. Do yourself a favor and don’t try it unless you really like to sand. Odds are you’ll end up working harder than you ever have for a mediocre result.
Until next time: Wax on, wax off, Miyagi.