# How full should I fill my curing jars?

> Fill curing jars about three-quarters full, loosely, so the buds don't crush and air can move around them when you burp. A packed jar holds wet pockets and flattens buds. A jar that is mostly empty holds a lot of air and swings humidity. Once the cure is done, after 2–8 weeks, fill storage jars fuller to cut the air in contact with the buds.

- Canonical: https://genetixbay.com/knowledge/answers/how-full-to-fill-curing-jars.html
- Topic: Harvest and cure · Type: Numbers
- Evidence: Grower practice · Status: Draft: awaiting expert review
- Full article: [Curing and burping: jars, humidity and how long](https://genetixbay.com/knowledge/harvest-cure/curing-burping.md)
- Also asked as: How full should curing jars be? | Should jars be three-quarters full? | Can I pack my jars tight? | Jar fill level for curing
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

Fill [curing jars](https://genetixbay.com/knowledge/glossary/curing-jar.md) about ¾ full, loosely, so the buds aren't crushed and the air can move when you [burp](https://genetixbay.com/knowledge/glossary/burping.md). Too full traps wet pockets. Too empty gives a big [air space](https://genetixbay.com/knowledge/glossary/air-filled-porosity.md) that swings the humidity. After the cure, fill storage jars fuller. *Grower practice*.

## Why

A cure is a slow decline in moisture. The bud's [water activity](https://genetixbay.com/knowledge/glossary/water-activity.md) should start around 0.62–0.65 and fall towards 0.55–0.58 over the weeks, inside the ASTM range of 0.55–0.65 [1]. Loose buds at about ¾ full give up their excess water evenly when you burp.

Packed jars stay wet in the middle. Moisture in a crushed mass of buds can't reach the air, and above water activity 0.68 flower needs more drying [2]. That is where mould and ammonia smells start.

The hygrometer needs room to read. Once a sealed jar has equilibrated, its [RH](https://genetixbay.com/knowledge/glossary/relative-humidity.md) divided by 100 equals the bud's water activity [1]. With a sensible fill it reflects the buds, not one wet corner.

Storage is different. After curing, the job is to slow oxidation: air turns [THC](https://genetixbay.com/knowledge/glossary/thc.md) into [CBN](https://genetixbay.com/knowledge/glossary/cbn.md) in storage, and light destroys THC [3]. A fuller, airtight jar kept in the dark limits both.

## The numbers

| Stage | Fill level | Why |
|---|---|---|
| Curing (weeks 1–8) | About ¾, loose | Air to burp, buds uncrushed |
| Storage after the cure | Fuller, still not crushed | Less air, less oxidation [3] |
| Practical jar size | 0.5–1 L glass | Equalises overnight, limits losses |
| Equilibrated [jar RH](https://genetixbay.com/knowledge/glossary/equilibrium-relative-humidity.md) | 55–65% | aw 0.55–0.65 [1] |

## What to do

1. Jar buds only when the stems snap and a sealed sample reads a stable 58–65% RH.
2. Drop buds in loosely to about ¾ full. Don't press them down.
3. Add a calibrated mini hygrometer, seal the jar, and label it with cultivar and date.
4. Burp for 10–15 minutes once or twice a day in week 1, every 2–3 days in week 2, then weekly.
5. Shake each jar gently when you burp so the buds turn.
6. After the cure, combine jars into fuller ones and store them cool and dark.

## Common mistakes

- Pressing buds down to fit one more in.
- One giant jar for the whole harvest.
- Reading the hygrometer straight after opening.
- Storing jars in sunlight.

## Related

- Full article: [Curing and burping](https://genetixbay.com/knowledge/harvest-cure/curing-burping.md)
- Answers: [mould in jars](https://genetixbay.com/knowledge/answers/mould-in-curing-jars.md) · [ammonia smell](https://genetixbay.com/knowledge/answers/ammonia-smell-in-jars.md) · [buds lost their smell](https://genetixbay.com/knowledge/answers/buds-lost-their-smell.md)
- Article: [long-term storage](https://genetixbay.com/knowledge/harvest-cure/long-term-storage.md)
- Terms: [curing jar](https://genetixbay.com/knowledge/glossary/curing-jar.md) · [burping](https://genetixbay.com/knowledge/glossary/burping.md)

## Follow-up questions

**What happens if I pack curing jars too tight?** Packing cannabis curing jars too tight crushes the buds and damages trichomes, and it leaves wet pockets where moisture can't escape, so a tight jar is more likely to grow mould. It also makes the hygrometer read the air around the edge rather than the bulk of the bud. Fill about three-quarters full, loosely, and shake the jar gently when you burp.

**Does jar size matter for curing?** Jar size matters less than fill level, but mid-sized airtight glass jars of about 0.5–1 litre are easiest for home cures. Each one holds a manageable amount, reaches equilibrium overnight and loses less if one jar goes wrong. Very large jars crush the bottom buds and take longer to equalise. Label each jar with cultivar and date.

**Should storage jars be full after curing?** Yes, once curing is finished, storage jars should be fuller than curing jars. After 2–8 weeks the buds no longer need burping, and less air in the jar means less oxidation of THC to CBN over months. Keep buds at water activity 0.55–0.65 in airtight, opaque or dark-stored glass, cool and out of light.

## Sources

1. ASTM D8197. Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower. https://store.astm.org/d8197-22.html
2. ASTM International, Standardization News. Two cannabis standards you should know about (salt-based humidity control sachets for aw below 0.68). https://sn.astm.org/node/2445/printable/print
3. Fairbairn JW, Liebmann JA, Rowan MG, 1976. The stability of cannabis and its preparations on storage. Journal of Pharmacy and Pharmacology 28(1):1–7. https://doi.org/10.1111/j.2042-7158.1976.tb04014.x