Official Luthiers Forum!

I've noticed that a lot of folks in these parts mention that they keep their shop RH at about 40%. Yet most manufacturers recommend keeping a guitar at as close to 50% as possible. In the cabinet biz we like to keep things a little on the dry side so that parts will swell slightly after install, rather than dry out. This helps keep frame and panel doors tight and rattle free. But I would have thought that this would not be a good idea for guitars, swelling would lead to the action getting higher and making set up difficult etc. I also noticed this in the martin owners manual "Martin keeps the factory at a constant 45-55 percent humidity and 72-77 degrees Fahrenheit." Just curious as to why the difference? Thanks.
Brian

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Brian

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Brian: You are correct in assuming that actions change as the RH shifts.Due to the cross grain bracing in the guitars construction it is important to keep the RH the guitar lives in somewhat close to the RH it was built in. Too wet and the grain tends to swell and push it's together,too dry and the grains dries and shrinks and this can lead to cracking due to the restriction of the bracing.Too dry much worst then too wet.I build in the winter at around 40RH and humidify if it drops too much below.Once the guitar is finished I have not worried about the rising RH of the summer-early fall and have had days that RH was 90+.Have not had problems with too wet but have with too dry. Few guitars live in ideal conditions thier whole lifetime.Just my take on a generally compromised problem.
Tom

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