Humidity is an important concern both for luthiers and for guitarists who own and play valuable instruments. Both have to deal with that substance called wood, which shrinks and expands as it releases or absorbs moisture. However, the humidity management challenges for the two are quite different.
For guitarists, maintaining a humidity range of 30% to 70% will probably keep your guitar safe, unless it’s a “wet” guitar or a “dry” one. You find that confusing? Goto “Humidity and Your Guitar’s Health” for more details, recently updated.
For luthiers, things are quite a bit more complex. “Humidity Management for Luthiers” is a full account of what I have learned from decades of experience and what I do nowadays to manage the humidity in my workshop.