Answer
Hold cannabis flower at 58% to 62% relative humidity (RH) and 60°F to 70°F. Use an airtight container, a calibrated hygrometer, and a two-way humidity pack sized to the container volume. Above 65% RH raises mold risk. Below 55% RH flower dries and loses terpenes.
diy cannabis humidor from cigar box
Target numbers
- Relative humidity: 58% to 62%
- Temperature: 60°F to 70°F
- Container fill: 75% to 80% of volume
- Hygrometer accuracy: within 2% RH after calibration
Tools
- Airtight glass jar with a gasket or a rigid plastic container
- Digital hygrometer that reads RH and temperature
- Two-way humidity pack rated at 62% RH
- Table salt for the hygrometer calibration test
Calibrate the hygrometer
- Put 1/2 cup of salt in a small dish. Add drops of water until the salt clumps.
- Place the dish and the hygrometer in a sealed plastic bag. Keep the bag at 68°F to 72°F.
- Wait 6 to 8 hours. A correct hygrometer reads 75% RH.
- Record the difference. Add or subtract that number from later readings.
Step by step
- Clean and dry the container. Residual water raises RH.
- Fill the container to 75% to 80%. Extra headspace slows humidity exchange.
- Place one humidity pack on top of the flower. Match pack size to container volume using the pack maker's chart.
- Seal the container. Store it in a dark cabinet at 60°F to 70°F.
- Read the hygrometer after 24 hours. Adjust with a second pack if RH is below 58%. Remove flower or open the lid for 15 minutes if RH is above 62%.
- Check RH every 3 days. Replace the pack when it turns rigid or dry.
Common mistakes
- Opening the container several times a day. Each opening exchanges air.
- Storing in a refrigerator. Condensation forms on flower when the jar warms.
- Adding orange peel or bread. Both raise mold risk.
- Using one small pack in a large container. The pack cannot hold the target RH.
- Placing the jar in sunlight or near a heater. Heat pushes RH down and degrades cannabinoids.
Concentrates and pre-rolls
Concentrates do not need 62% RH. Store them in a sealed container at room temperature, away from light. Water hash and rosin belong in a freezer. Pre-rolls dry faster than flower. Keep them in the same humidor at 58% to 62% RH and smoke them within 30 days.
Rehydrating dry flower
Add a 62% pack to the jar. Wait 24 to 48 hours. Check RH every 12 hours. Stop when RH reaches 58% to 62%. Flower that crumbles to powder may not recover terpenes.