Generally speaking, the thinner the finish the better the sound. This is because a thin finish allows the soundboard of the guitar to resonate more freely with minimal restriction. A thick, heavy finish prevents the soundboard of the guitar from moving as freely and thus dampens the sound.

Although we know that thinner finishes are preferrable, it’s impossible to directly compare the effect of the finish from one guitar to another as every guitar is different. It’s also not possible to compare the sound of different finishes on the same guitar, as removing a finish from a guitar will inevitably remove some of the wood during the cutting back process. This means the new finish would be applied to a slightly altered instrument and would therefore not offer a fair comparison.

There is much debate over exactly which finish sounds better, and this looks likely to continue as there is no definitive way to fairly compare finishes side by side.