Here at MayosMusic, in addition to offering great guitar, bass, ukulele, banjo and autoharp lessons, plus complete luthier services that include guitar, string instrument and amplifier repair/restorations, we are also a great resource service.
Below is a discussion on the torrefaction process as applied to the making of new guitars and the effect this process has on the guitar's tone and sing quality.
Torrefaction is a process where wood has been heated in a kiln to remove moisture. Guitars that feature torrefied wood (most often in the top or soundboard) have more of an aged sound.
Torrefaction is a very unique and specific method that heats the wood in the absence of oxygen. This process removes most of the moisture and breaks down some of the original plant matter of the wood, which leaves the wood's chemical properties very close to a naturally aged (for decades) guitar top. This process of torrefaction leaves the guitar top/soundboard stiffer, thus allowing it to vibrate more freely.
The process of torrefaction adds greatly to the guitar's tone and sing quality. The guitar top will vibrate more freely, give louder volume and with a deeper and more full bodied sound similar to that of a vintage instrument.