Quote:
Originally Posted by Mark Stone
The last few days just out of curiosity, I watched factory tours of Martin, Taylor and Gibson on YouTube. I think all of them were from Harmony Central. All were entertaining and enlightening. Out of the three, Gibson is the most hands-on, however I think it's a stretch to call any of these manufactured guitars "hand-made" 
On the Martin tour, the tour guide explained that the wood comes in to the factory at about "40% Moisture Content", and then over a period extending at least one year they use a kiln and special room(s) to lower moisture content to 6% before they actually use the wood to construct guitars. He explained that 6% is basically as low as RH gets in the real world. The purpose, according to the tour guide, was to prevent the wood from cracking because of low humidity after the instruments are purchased.
This was interesting, and was not mentioned in either the Gibson or Taylor online tours. Does this mean Martin guitars don't really need humidification? There's a lot of real world connotations here, perhaps - This detail seems to mean that it is unnecessary to "anally" keep a Martin instrument at 45%↑↓ RH as you would need to do with a Gibby or Taylor. |
One of our regular posters, "redir", recently posted a good explanation. The moisture held by the cells is cellular moisture, and this is likely the 6% that your are hearing. Relative humidity is absorbed and dispelled by the "spongy" fibres of the wood, rather than in and out of the cellular walls.
So, regardless of the RH of the air (to which the wood will reach equilibrium in relatively short amount of time), the cellular moisture content of the wood should be low before building. RH for building instruments is commonly near 40%, with some building in more or less humid environments depending upon the target market location.