Guitar finish is another topic where opinion runs strong and the science is genuinely nuanced. Does the type and thickness of finish on a guitar actually change how it sounds? Here's a balanced look at what's really going on.

What finish is actually for

First and foremost, finish protects the timber from moisture, dirt and general wear, and it's a major part of a guitar's visual appeal. Any tonal discussion is secondary to that core protective function, and no builder is going to leave a guitar completely unfinished just to chase a theoretical tonal gain.

The case that finish matters

Since the top is the primary vibrating surface producing an acoustic guitar's sound, and finish sits directly on that surface, it stands to reason that a thicker, stiffer finish could dampen vibration slightly compared to a thin, more flexible one. This is the reasoning behind why some high-end builders use very thin nitrocellulose lacquer or oil finishes, aiming to add as little mass and stiffness as possible.

The case that it's a minor factor

Modern finishes, including thin polyurethane and satin finishes, are applied in genuinely thin layers on most well-built guitars, and the actual mass added is small relative to the top itself. Bracing pattern, top wood choice and overall build quality are widely considered to have a far bigger impact on tone than finish type or thickness.

Where the debate gets murky

Part of the difficulty is that guitars built with different finishes are often also different in other ways, different bracing eras, different top woods, different builders, which makes it genuinely hard to isolate finish as the single variable responsible for a perceived tonal difference.

A reasonable way to think about it

Finish likely has some effect on tone, but it's almost certainly a smaller factor than tonewood, bracing, body size and overall construction quality. It's a legitimate detail for a serious player or collector to be curious about, but not something worth losing sleep over when choosing between two otherwise excellent guitars.