Your acoustic guitar is a living instrument. The tonewoods that give it warmth and resonance are also vulnerable to humidity changes that can crack, warp, or swell the body if left unchecked.
The Target Range
Acoustic guitars are happiest at 45-55% relative humidity. This is the range in which most tonewoods are stable — neither losing nor gaining moisture.
What Happens Below 40% (Too Dry)
- Fret ends become sharp as the fretboard shrinks laterally - Top cracks develop along the grain - Action lowers as the top sinks - Bridge may crack or lift - Nut and saddle slots may develop stress fractures
What Happens Above 65% (Too Humid)
- Top swells, raising action uncomfortably - Neck may bow forward - Finish may blister or crack - Mold can develop inside the body
Seasonal Protection
Winter (Dry): Use an in-case humidifier (soundhole, case, or both). Monitor with a hygrometer.
Summer (Humid): Store in air-conditioned spaces. Use a dehumidifier in excessively humid climates.
Symptoms to Watch For
- Fret ends feeling sharp or scratchy - Action that changes without adjustment - Buzzing or dead notes that weren't there before - Visible cracks in the top, back, or sides
When to See a Luthier
If you notice cracking or extreme action changes, take your guitar to a professional immediately. Early intervention prevents catastrophic damage.
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Our Pro Concierge can help you identify symptoms and recommend next steps for your specific guitar situation.
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