Lots of fans of vintage or high-end (that is, expensive) new guitars will tell you that they wouldn’t be caught dead playing a guitar with a finish done in anything other than nitrocellulose lacquer (nitro for short), and this finish has indeed earned some kudos as the coating of choice used by the most beloved electric-guitar makers in the golden age of the instrument.
When applied correctly, nitrocellulose provides a thin, hard finish that not only ages beautifully as your guitar ages (gaining wear and patina that guitarists seem to love) but also is reputed to allow the wood of the guitar to resonate freely. Many players believe that this finish, therefore, enhances a guitar’s tone, and lots of makers still use it today as a result.
The thing is, plenty of extremely talented makers of extremely expensive and great-sounding guitars are perfectly happy using polyurethane finishes, too, and find that they do nothing to impede a guitar’s resonance when sprayed on thinly.
So-called poly finishes got a bad rap in the ’70s when Fender started applying a thick, plastic-y polyester coating that inhibited the resonance of some guitars — guitars that probably weren’t tone monsters in the first place, given the general decline in Fender quality during that era.
The finish wore extremely well, retained vibrant color, and was relatively easy to apply, so it must have seemed to Fender’s then owner, CBS, like a win-win situation. However, the sonic disparity between lesser-quality, polyester-dressed Fenders and the company’s better creations was noticed by many players, even if it wasn’t entirely the fault of the finish.
The polyurethane finish previously used by Fender in the late ’60s — and popular again with many makers today — is a very different beast from polyester. Urethane, as it is often called, is a versatile liquid plastic resin invented in Germany in the 1930s.
It yields a hard, attractive, and protective finish even when sprayed in just a couple of thin coats, and is less labor intensive to apply than nitrocellulose. The fact that respected makers such as Paul Reed Smith, Nik Huber, and many others have long favored urethane tells us that you can get good results with something other than nitrocellulose.