# Curing and burping: jars, humidity and how long

> Curing is a slow, steady decline in the bud's moisture content and water activity, not a constant hold: start around aw 0.62–0.65 and let it settle towards 0.55–0.58 over two to eight weeks, burping daily at first, then weekly. Jar RH is only a proxy for the bud, valid once a sealed jar has equilibrated (aw ≈ RH / 100). Check with the stem snap, an equilibrated hygrometer and weight. Humidity packs are a marketing gimmick; if a jar is too dry, add a fresh bud.

- Canonical: https://genetixbay.com/knowledge/harvest-cure/curing-burping.html
- Category: Harvest and cure · Level: Beginner
- Evidence: Grower practice · Status: Draft: awaiting expert review (some figures are being checked)
- Stage: Cure · Systems: Any system
- 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)"

## Questions and answers

**How long should I cure cannabis?** Cannabis should cure for at least 2 weeks, and 4–8 weeks is common, according to grower practice. Over that time the bud's water activity should fall slowly from about 0.62–0.65 towards 0.55–0.58. Longer cures help within reason by letting aroma settle and limiting further [terpene loss](https://genetixbay.com/knowledge/glossary/terpene-loss.md), but curing chemistry is not well studied, and no cure can rescue a badly dried crop.

**How often should I burp jars?** Burp curing jars by opening them for 10–15 minutes once or twice a day in the first week, every 2–3 days in the second week, and weekly after that. Sniff each time: an ammonia or musty smell means the buds are too wet and at risk of mould, so spread them out to dry immediately rather than just burping more.

**What humidity should my curing jars be?** Curing jars should read 55–65% RH once sealed and left undisturbed for 12–24 hours, starting near 62–65% and drifting slowly towards 55–58%. Jar RH is only a proxy for the bud's water activity and is valid only after equilibration; a reading taken right after burping measures the air. If an equilibrated jar reads above about 65–68%, take the buds out and dry them more.

**What water activity should cured buds be?** Cured cannabis buds should sit at a water activity of 0.55–0.65, the range set by the ASTM D8197 standard to guard against mould without making flower brittle. Start the cure near 0.62–0.65 and let it fall slowly to about 0.55–0.58; above 0.68 the flower needs further drying. A dedicated water-activity meter is the gold standard for measuring it.

**What [moisture content](https://genetixbay.com/knowledge/glossary/moisture-content.md) should cured cannabis have?** Cured cannabis at water activity 0.55–0.65 holds roughly 8–12% water by weight, though the figure depends on the measuring method. One lab's method-validation data puts cured flower at 5–9% by water-specific methods, while the common 10–12% figure partly comes from hot-oven testing that also counts lost terpenes as water. That is why water activity, not moisture percentage, is the standard.

**How do I know my buds are dry enough to jar?** Buds are dry enough to jar when small stems snap cleanly with a little fibre instead of bending, the flower springs back when squeezed, and a sample sealed in a jar for 12–24 hours reads a stable 60–65% RH. By then the flower usually weighs about 20–25% of its [wet weight](https://genetixbay.com/knowledge/glossary/wet-weight.md). If a jar spikes to 75% or more overnight, the buds went in too wet.

**Do humidity packs work for curing?** Two-way humidity packs are a marketing gimmick in GenetixBay's view, not a better way to cure. The only data claiming a terpene benefit is a pack maker's own company-commissioned, non-peer-reviewed test, and no independent study exists either way; in the founder's experience packs cost terpenes. If a jar drops below about 55%, add a fresh, slightly moister bud for a day instead.

**Should jar humidity stay constant during a cure?** Jar humidity should not stay constant during a cure. Curing is a slow, steady decline in the bud's moisture content and water activity, from about aw 0.62–0.65 at the start towards 0.55–0.58 over several weeks, and holding one number for months is a common mistake. Weighing jars weekly confirms the decline: small, steady losses are right, and a gain means moisture got in.

**Is water curing worth it?** Water curing is not worth it according to GenetixBay, which labels it contested and does not recommend it. Neither water curing nor [freeze drying](https://genetixbay.com/knowledge/glossary/freeze-drying.md) is proven to give better flower than a slow hang dry in the dark followed by a jar cure, which remains the standard. A cure works by slowly lowering the bud's water activity, from about 0.62–0.65 towards 0.55–0.58.

**Why does my cure smell like hay?** A cure that [smells like hay](https://genetixbay.com/knowledge/glossary/hay-smell.md) points to bacteria, [over-drying](https://genetixbay.com/knowledge/glossary/over-drying.md) or drying too fast, and in GenetixBay's experience that smell never truly comes out; curing won't remove it. Prevent it with a slow 7–14 day dry and by never letting buds fall below water activity 0.55. An ammonia or musty smell is different: it means the buds are too wet and at risk of mould.

**Can curing fix a bad dry?** Curing cannot fix a bad dry. Long cures help within reason, letting moisture equalise and aroma settle, but the harsh smoke and hay or grassy smell from a 3-day hot dry stay with the flower. A cure adds no terpenes either; it only limits further loss. Get the dry right first: in the dark, at about 15–21 °C and 55–62% RH, for 7–14 days.

**Short answer.** Cure the **bud's moisture**, not the jar's air. Put properly dried buds (small stems snap, aw ~0.60–0.65) loosely into airtight jars **about ¾ full**, with a salt-tested hygrometer. Keep jars dark at **15–21 °C (60–70 °F)**. **Burp** (open for 10–15 minutes) **once or twice a day for the first week**, then every few days, then weekly. Start with the buds at about **aw 0.62–0.65** and let them fall slowly towards **0.55–0.58** over the cure: curing is a steady decline, not a constant hold. The jar's RH tells you the bud's aw **only once the sealed jar has equilibrated** (aw ≈ RH / 100). If an equilibrated jar reads **above ~65–68 %**, take the buds out and dry them more; ASTM notes aw above 0.68 calls for further drying [1][2]. Cure **2–8 weeks**. Smoother smoke and rounder aroma are widely reported, but the chemistry of curing is *Grower practice*, not well studied.

> **House position: a cure never fixes a bad dry.** Long cures help, within reason. But a **hay smell** means bacteria, over-drying, or drying too fast, and it never truly comes out. Get the [dry](https://genetixbay.com/knowledge/harvest-cure/drying.md) right first.

> **House position: curing is a slow decline, not a hold.** A cure slowly reduces the bud's moisture content and water activity over time; it doesn't hold them constant. Start at the top of the range (aw ~0.62–0.65) and let it fall steadily towards ~0.55–0.58 over the weeks. **Humidity packs are a marketing gimmick.** The only data saying they help is a pack maker's own test, and in the founder's experience they cost you terpenes. If a jar has gone too dry, put a fresh, slightly moister bud in with it for a day instead. (Packs vs a fresh bud vs nothing is an open GenetixBay trial.)

## The bud, not the jar: moisture content and water activity

What you are curing is the **bud**. Two numbers describe its water:

- **Moisture content (MC):** how much water is in it, as % of its weight (w/w).
- **Water activity (aw):** how "available" that water is, from 0 to 1.0. It is what mould and bacteria respond to, and it is what the ASTM D8197 range (**0.55–0.65**) is written in [1].

**Jar RH is only a proxy.** A hygrometer measures the air in the jar, not the bud. Once a sealed jar has **equilibrated** (the reading has stopped moving, usually after 12–24 h undisturbed), the air and the bud agree, and **aw ≈ equilibrium RH / 100**: a stable 60 % means the bud is at about aw 0.60. Read it straight after burping or after you've just filled the jar and it tells you about the air, not the flower. Hygrometers also drift; salt-test yours.

**What that means in moisture.** At aw 0.55–0.65, cured flower holds roughly **8–12 % water by weight** [5]. The exact link between aw and MC (the moisture sorption isotherm) differs a little by cultivar and bud density, which is why aw, not %, is the standard.

### How to check the bud

| Check | How | What "ready" looks like |
|---|---|---|
| **[Stem snap](https://genetixbay.com/knowledge/glossary/stem-snap-test.md)** | Bend a small stem from inside the jar | Snaps cleanly with a little fibre; a bend means too wet, a powdery crumble means too dry |
| **Equilibrated hygrometer** | Seal the jar, leave it untouched 12–24 h, then read | Stable 55–65 % (aw 0.55–0.65); start the cure at the top of that, let it fall slowly |
| **Weight** | Weigh a tagged branch or a jar's buds wet, then track | Finished flower ends at roughly **20–25 % of its wet weight**; a slow, steady fall in weight over the cure is the "decline" you want |
| **Feel** | Squeeze a bud gently | Springs back; not spongy, not crispy |

A dedicated water-activity meter is the gold standard, but an equilibrated, salt-tested hygrometer gets you close enough at home.

## What's happening

- **Moisture equalisation:** after drying, the core of a bud is wetter than the outside. Sealed, the moisture redistributes; burping releases the excess so the jar doesn't climb into mould territory.
- **Chlorophyll and sugars:** growers attribute the loss of a fresh "green" note to slow breakdown of chlorophyll and starches during a slow dry and cure. This is plausible but not well documented in cannabis (*Grower practice*).
- **Hay smell:** a true hay smell comes from bacteria, over-drying or drying too fast. The cure won't remove it (house position).
- **Terpenes:** volatile [monoterpenes](https://genetixbay.com/knowledge/glossary/monoterpene.md) keep escaping during drying and storage, with [sesquiterpenes](https://genetixbay.com/knowledge/glossary/sesquiterpene.md) becoming a larger share [3]. Terpenes are more affected by drying method than by storage in hemp; [cannabinoids](https://genetixbay.com/knowledge/glossary/cannabinoid.md) more by storage [4]. A cure doesn't add terpenes; it limits further loss and lets aroma settle.

## Numbers that matter

| Parameter | Target |
|---|---|
| Jar fill | ~¾ full, loose |
| Bud aw (equilibrated jar RH / 100) | Start 0.62–0.65, decline slowly to 0.55–0.58 (0.55–0.65 overall) [1] |
| Bud moisture content | ~8–12 % w/w at that aw (method dependent) [5] |
| Too wet | Equilibrated jar > 65–68 % → remove and dry [2] |
| Too dry | < 55 % → add a fresh, slightly moister bud for a day; no humidity packs |
| Finished weight | Roughly 20–25 % of wet weight |
| Temperature | 15–21 °C (60–70 °F) |
| Burping | Week 1: 1–2×/day; week 2: every 2–3 days; after: weekly |
| Duration | 2 weeks minimum; 4–8 weeks common |

- Freeze drying and water curing: *Contested*; not recommended (see [drying](https://genetixbay.com/knowledge/harvest-cure/drying.md)).

## How to do it

1. Check dryness on the bud: stems snap, then seal a sample jar with a hygrometer for 12–24 h untouched. Only that equilibrated reading counts.
2. Fill jars ¾, add a calibrated mini hygrometer, seal, label with date and cultivar.
3. Burp on schedule; sniff each time. An ammonia or musty smell = too wet, mould risk: spread buds out to dry immediately.
4. Don't add humidity packs: they're a marketing gimmick (house position). Let the bud's aw drift down slowly, reading the jar only after it has sat sealed long enough to equilibrate; if it drops below ~55 %, add a fresh bud for a day.
5. Track weight: weigh each jar's buds when you fill it and again each week. Small, steady losses mean the cure is declining as it should; a gain means moisture got in.
6. After the cure, move to [long-term storage](https://genetixbay.com/knowledge/harvest-cure/long-term-storage.md).


> **Greenleaf's standing challenge: [darkness before harvest](https://genetixbay.com/knowledge/glossary/darkness-before-harvest.md).** Putting plants in 24–72 h of darkness before the chop is a *Myth*, and the founder's verdict is "complete and utter nonsense": why cut [photosynthesis](https://genetixbay.com/knowledge/glossary/photosynthesis.md) in the most critical part of the life cycle, while the plant is still finishing its resin? For more than 20 years the founder has offered a standing challenge: find a peer-reviewed study showing a benefit (not a single-plant study, not biased or skewed) and a 50-pack of seeds is yours, no questions asked. Nobody has claimed it.

## Common mistakes

- Jarring buds too wet (the jar spikes to 75 %+ overnight).
- Packing jars tight.
- Leaving jars in sunlight.
- Expecting the cure to fix a 3-day hot dry, or a hay smell. It won't.
- Plastic bags (static strips trichomes; poor vapour barrier).
- Reading the hygrometer right after burping and calling it the bud's humidity. Only an equilibrated jar tells you about the bud.
- Trying to hold the jar at one number for months.

## Evidence

The aw range and the "dry further above 0.68" rule are *Established* standards [1][2]. Terpene loss over time is *Supported* [3][4]. Burping schedules, duration and sensory claims are *Grower practice*. aw ≈ equilibrium RH / 100 is the definition of water activity, so an equilibrated jar reading is a fair proxy; the moisture-content figure for a given aw depends on the measuring method (*Supported* by one lab's method-validation data [5]). A slowly declining bud aw rather than a constant hold: house position (*Grower practice*). Humidity packs are a marketing gimmick (house position). The only pro-pack data is the manufacturer's own: a pack maker reports higher terpene levels with its packs in a company-commissioned jar test (not peer reviewed), and we have not found an independent study either way. ASTM D8197 lists salt-based sachets as one way to bring under-range flower back up [2]; that is a storage-spec convenience, not evidence that packs improve flower. Freeze drying and water curing: *Contested*, not recommended.

## 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. Ross SA, ElSohly MA, 1996. The volatile oil composition of fresh and air-dried buds of Cannabis sativa (monoterpene loss on drying and storage). Journal of Natural Products 59(1):49–51. https://diverdi.colostate.edu/C442/references/analysis/GC/j_nat_prod_1996_v59_p49.pdf
4. University of Georgia (thesis). Effects of drying method and storage on cannabinoids and terpenes in hemp (terpenes affected by drying, cannabinoids by storage). https://openscholar.uga.edu/record/27813
5. Modern Canna Laboratories. 2025. Validation of moisture content and water activity methods in cannabis flower (method-validation white paper; cured flower typically 5-9 % moisture by water-specific methods at aw 0.45-0.60; 103 °C oven loss-on-drying overstates moisture). https://moderncanna.com/wp-content/uploads/2026/04/Method_Validation_Study_Moisture_Content_and_Water-Activity_in_Cannabis_Flower.pdf