Quick answer: The dose is simple: one 60 g Humidi-Cure® 49% pack per guitar or violin case, and two packs for cello cases, large archtops, double basses and display cabinets. Bigger enclosed volume or a leakier case means more packs; the indicator card is the final judge — if it can’t hold ~50%, add a pack or fix the seal.
“How many do I need?” is the most-asked question and the easiest to over-think. Two-way packs work on the air volume they have to control and how fast that air leaks out, so the answer scales with case size and seal quality — not with how expensive the instrument is. Here is the whole decision in one table, then the reasoning.
| Instrument / enclosure | Packs (60 g) | Notes |
|---|---|---|
| Acoustic / classical / electric guitar case | 1 | Standard dose; the everyday case |
| Violin or viola case | 1 | Small volume; one pack is plenty |
| Ukulele / mandolin / banjo case | 1 | Small-bodied; one pack, watch the wet side |
| Large archtop / jumbo / resonator case | 1–2 | Bigger cavity; add a second if the card drifts |
| Cello case | 2 | Large volume needs two |
| Double bass case / trunk | 2–3 | Very large; verify with the card |
| Display cabinet or wardrobe (per unit) | 2+ | Scale to the volume; one system per enclosed space |
| Leaky / gappy case (any instrument) | +1 | Poor seal depletes packs faster — fix the seal or add a pack |
The three variables that change the dose
Enclosed volume. A pack conditions the air around it. A violin case is a shoebox; a cello case is a wardrobe. More air, more packs.
Seal quality. This is the single biggest factor in how long a pack lasts and whether one is enough. A tight, gasketed hard case holds the setpoint on one pack for about 3 months; a case that closes with visible gaps leaks conditioned air and needs more frequent replacement or a second pack. Why airtightness dominates pack life is explained in the how-it-works article.
Climate severity. A brutal dry winter or a tropical monsoon makes the pack work harder, shortening its life — not usually changing the pack count, but the replacement cadence. Trust the card, not the calendar.
How to confirm you got it right
Put the dose in, close the case, and read the indicator card after 24 hours. Around 50% means the dose is correct. If the card sits at or above 60% (in a humid climate) or at or below 40% (in a dry one) after a day or two with the case closed, either the seal is leaking faster than the pack can keep up — check the case — or you need one more pack. The reading routine is in the card guide. Storing an instrument for months? Buy the packs for the whole window up front — the sealed-case storage method has the counting worked out.
Buying for many instruments
A collection, a teaching studio, a band’s backline or a store’s stockroom multiplies the same simple math: one pack per standard case, two per large one, quarterly replacement. That is a predictable per-case cost that any shop or school can budget — the fleet version is in the music-store program, and wholesale tiers are at wholesale programs.
For players: one 60 g pack per guitar or violin case, two for cello cases and cabinets. Get the right dose: 60 g Humidi-Cure® 49% packs →
Buying for a shop, school or fleet of cases? Wholesale tiers and custom RH programs are available — see wholesale programs or write to info@atmosiscience.com.
FAQ
Can I use more packs to make it last longer?
Two packs in a guitar case will hold the setpoint longer between replacements, yes — but one is enough to reach 49%. Extra packs buy runtime, not a different humidity.
Half a pack for a tiny ukulele case?
Use a whole pack — don’t cut it open. One 60 g pack is the smallest sensible dose and it simply lasts a bit longer in a small case.
Two instruments in one big case — how many?
Dose for the case volume, not the instrument count — a large double case is typically two packs, with one card at eye level.
My card won’t hold 50% no matter how many packs.
That is a seal problem, not a dose problem — conditioned air is leaking out. Gasket-tape the case rim or upgrade the case; packs can’t out-run a leaky lid forever.
Tell us your cases and we'll size the dose (and the reorder)
List your instruments and case types and the team will confirm exactly how many packs you need now and per quarter — no over-buying — with bulk pricing if you are covering several.
Prefer email? Write to info@atmosiscience.com — a specialist replies within one business day.
