Wood breathes with humidity — too dry and the top cracks; too damp and glue joints fail. Two-way humidity packs release or absorb moisture as needed, locking your case in a safe range. The most worry-free guitar maintainance solution out there.
1. Setup
Tear off the outer plastic wrap but never puncture the brown inner pouch — leakage will ruin your guitar. Slide the 2 way humidity pack into its fabric holder, which prevents leaks, allows breathability, and stops crushing. Not optional.
2. Placement
Full-size acoustic: drape a two-pack holder over the soundhole in an inverted U, hanging into the chamber between strings. One more humidity control pack under the headstock — don't let the headstock press on it. Electrics go in the accessory compartment or by the neck. Keep the case lid closed at all times, or humidity packs deplete rapidly.
3. Which Version
Most areas: 49% RH. Southern plum rains, coastal zones, or consistently above 50% humidity: choose 49% HA (High Absorption) — resists saturation. 58% is only for extremely dry northern winters short-term.
4. How Many
Full-size acoustic hard case: minimum 3 packs, 4 recommended (size 60g/67g/75g). 3/4 travel guitars: 2–3. Electrics: 2. Ukuleles: 1–2. Don't substitute small packs (8g/10g) — those are for cigar boxes. Total capacity falls far short, and scattered placement causes uneven local humidity across the guitar body.
5. Replacement
Officially replace every 90 days. Touch test: rock-hard throughout means it's dead. HA version is the opposite — swollen and bulging means replace. Mark the date on new humidity packs with a pen.
Bottom Line
Full-size acoustic hard case: four large 49% humidity packs in holders, two draped over the soundhole, one under the headstock, lid always shut, replaced every three months. Let 2-way guitar humidity control packs do the rest.
