Mold at “Perfect” Settings? A Troubleshooting Guide for 68% RH & 65°F
Seeing mold while your gauges read ~68% RH and ~65°F is frustrating—but common. Readings can be off, conditions aren’t uniform, and cigars may arrive “wet.” Use this guide to uncover hidden issues and fix them.
Why “Ideal” Isn’t Always Ideal
- Averages hide pockets: A hygrometer reports an average, not what’s happening in corners, deep trays, or by the lid.
- Placement matters: Sensors near devices or doors read differently than sensors in crowded trays.
- History matters: “Wet” arrivals can push a marginal setup over the edge.
Instrument Error & Placement
- Calibrate quarterly: Salt test or manufacturer method; keep a second meter to cross-check.
- Map the box: Move a small sensor through lid/back/bottom for 24h each to detect microclimates.
- Avoid wet bias: Don’t mount sensors directly above humidifier outlets or on the coldest wall.
Microclimates in the Humidor
- Overpacking: Tight trays block circulation; leave air gaps.
- Blocked vents/seams: Ensure nothing presses against vents or seals.
- Vertical stratification: Upper shelves can run moister; rotate stock between levels.
Pre-Existing Moisture & Dormant Spores
- “Wet” boxes: Some shipments leave factories/retailers above your target RH—quarantine and acclimate.
- Dormant spores: Stable conditions determine whether they bloom; keep RH/temperature steady.
Ambient Influences
- Room swings: Sun, HVAC, appliances, or exterior walls can create condensation pockets.
- Safer location: Interior room, no direct sun or vents; steady temperature.
Handling & Rotation
- Clean hands/tools: Avoid transferring oils/contaminants.
- Rotate quarterly: Repack lightly; inspect caps/feet and corners under trays.
10-Step Audit (In Order of Impact)
- Cross-check RH with a second calibrated meter.
- Temporarily lower target to ~65% RH for one week (brief venting; reduce humidification media).
- Reduce density: lighten any overpacked tray to improve airflow.
- Relocate the humidor to a stable interior spot (no sun/HVAC drafts).
- Clean reservoirs; replace old or oversaturated media.
- Retire sponges/foam; switch to inert beads/polymers or two-way humidity packs.
- Map microclimates with a mobile sensor; adjust placement/air gaps accordingly.
- Quarantine new boxes for 7–14 days to acclimate before mixing.
- Inspect seals/hinges; replace gaskets on cabinets if needed.
- Persistent issues? Dry-down and re-season (see remediation guidance).
When to Reset & Re-Season
- After a mold event or prolonged over-humidity.
- If cedar feels damp or readings won’t stabilize.
- Re-season gently—avoid over-wetting wood; restabilize before restocking.
Bottom Line
“Perfect” numbers mean little without uniformity and stability. Fix instruments, flow, and media—then keep cigars on a calm, consistent path.