Do poly finishes "break in" for enhanced tone and resonance over time?

[PeteyPower16]

Do poly finishes "break in" for enhanced tone and resonance over time?

As a new guitar ages, the instrument usually becomes more resonant. How much of this is due to aging wood and loosening of braces?

Can any of the increased tone and resonance be attributed to the poly finish "breaking in?"

[colins]

Poly finishes are designed to cure (polymerise and lose their volatiles) in a very short time period. They are not designed to be under any stress once they are applied.

On the other hand, wood is a complex mixture of polymers (cellulose and hemicellulose) in a somewhat crystalline matrix of lignin, plus residual moisture, plus a wide range of volatile compounds that vaporise and leave the wood over time. Wood can also include stresses.

So the aging effect over an extended time, with the ability for volatiles to be expelled and playing vibrations to modify any inherent stresses is, IMHO, far more likely to be due to the wood than the poly finish.

(Volatiles are chemical compounds that gradually vaporise. Torrefaction is a well-known method of releasing volatiles from wood that has recently been applied to wood for guitars. As the temperature of torrefaction is increased it progressively expels larger volatile compounds with higher temperature points for vaporisation.)

[PeteyPower16]

Originally Posted by colins

Poly finishes are designed to cure (polymerise and lose their volatiles) in a very short time period. They are not designed to be under any stress once they are applied.



On the other hand, wood is a complex mixture of polymers (cellulose and hemicellulose) in a somewhat crystalline matrix of lignin, plus residual moisture, plus a wide range of volatile compounds that vaporise and leave the wood over time. Wood can also include stresses.



So the aging effect over an extended time, with the ability for volatiles to be expelled and playing vibrations to modify any inherent stresses is, IMHO, far more likely to be due to the wood than the poly finish.



(Volatiles are chemical compounds that gradually vaporise. Torrefaction is a well-known method of releasing volatiles from wood that has recently been applied to wood for guitars. As the temperature of torrefaction is increased it progressively expels larger volatile compounds with higher temperature points for vaporisation.)

That’s an excellent scientific answer, and exactly the kind of detail to help answer my wondering. Thank you!

[Steve DeRosa]

Extrapolating from colins' fine scientific analysis to a more pragmatic domain, advances in both materials and manufacturing methods also mean that modern poly finishes can be applied extremely thin - which, while their actual "contribution" to an instrument's tone over time is debatable, as a whole they no longer inhibit top vibration as they did 25+ years ago...

[ssynhorst]

Very good, but that is just the finish. There are other issues in the aging of the guitar top, the braces and the glues that hold them all together, which are probably much more important than just the varnish. - Steve