How to Cure Weed: Curing Humidity, Burping and When It's Done

The plain answer on curing weed humidity: aim for 58–62% relative humidity (RH), read on a hygrometer after the jar sits sealed overnight with no humidity pack inside, a band within ASTM D8197, ASTM International's standard for dry cannabis flower. To cure weed, put already-dry buds in airtight glass jars about three-quarters full, dark at 60–70 °F; burp daily in week one, then whenever the morning reading tops 62% (our margin; a practitioner book's trigger is 65%); and call it done when the sealed reading holds in band across checks days apart. Practitioner books call jars usable in two to three weeks; "four to eight weeks" is grower consensus, and no study shows longer cures improving anything.

An honesty note: ColaXpress has no harvest, jars or other containers, humidity packs, hygrometers, purchased flower or packaging, and ran no lab tests; we cured, measured and stored nothing. Every figure is credited; our arithmetic and house choices are labelled. Drying lives in our drying humidity guide, the timeline in how long to cure weed, the quick chart on the drying and curing environment page.

Curing Humidity at a Glance

Readings: sealed overnight, steady room temperature, no humidity pack. On the first night after jarring, the rule from our drying humidity guide applies instead: 62–65% means one more day of drying, 65% or more back on the line. ASTM's limits are water activity (aw), the RH that air sealed with the flower settles at, divided by 100 (FDA): 0.65 is 65%.

How to Cure Weed in Jars, Step by Step

• Salt-check the hygrometer: 24 hours sealed in a bag with damp table salt, which holds about 75% RH (Greenspan 1977, US National Bureau of Standards). Apply that offset to every later reading.
• Start with a finished dry: small stems snap, bigger ones flex (a practitioner cue for when to start checking), and a test jar sealed overnight reads 58–62%, or 55–58% on the dry side (buds ready for jars). A jar doesn't finish a wet dry; the cure jars' first night is the dry's last test (note above the table).
• Use airtight glass about three-quarters full, buds loose enough to roll: common practice and the figure in Grove Bags' jar guide (vendor). Ed Rosenthal and David Downs' Marijuana Harvest (Quick American, 2017, ISBN 978-1-936807-25-3) says no more than half; no study compares fill levels.
• Seal and read the next morning (house practice), sensor in the headspace, not in the buds, jar untouched at steady room temperature. Overnight matches the FDA's "several hours" for headspace: probes in sealed 16-oz Mason jars over salt slurries at 22 °C levelled off in about 45 minutes (Cheng and colleagues, 2025, University of Minnesota), but ground flower over salts took 72–144 hours (Modern Canna Laboratories white paper, 2026, not peer-reviewed), so the done test repeats over days. Don't hold the jar: a 1 °C (1.8 °F) flower-to-air difference could shift the reading about 0.05 aw by the FDA's extrapolation from high-moisture foods: 5 RH points by our arithmetic, wider than the whole target.
• Store dark at 60–70 °F (practice; see below).
• Burp by the reading (lid off about five minutes, then reseal; smell it). Week one: read each jar sealed every morning, then burp it (below 58%, leave it sealed); above 62%, burp again that evening. At 65% or more, burp at once (Rosenthal and Downs' trigger); still above 65% next morning, or above 68% ever, means a day back in the drying space (our rule). Five minutes is our choice; published practice runs from 2–3 minutes (Grove Bags) and 4–5 (Rosenthal and Downs, day one) to 30 minutes a day (Noelle Joy's 2025 University of Georgia dissertation) and about 1–2 hours a day (NC State Extension).
• Taper (ours, untested, within the common daily-to-every-few-days range): from week two, burp only above 62%; once readings hold at 58–62%, read every two or three days, then weekly.
• Call it done when the test below passes; practitioner books expect two to three weeks.

Why 58–62%: Water Activity and Mold

ASTM D8197-22 requires dry cannabis flower below aw 0.65 against mold and above 0.55 against breakage, with more drying above 0.68: about 55–65% RH in a jar at equilibrium.

58–62% leaves room for meter error. Makers rate consumer hygrometers at about ±1.5–3% RH (their stated specs), so a jar reading 62% could really be 65% (our arithmetic); retail units have tested worse (see our drying humidity guide). The top edge is no comfort zone: Punja and colleagues (2023, Frontiers in Microbiology), studying commercial cannabis, write that xerotolerant (dry-tolerant) Penicillium and Aspergillus molds can grow and survive at aw 0.62–0.70. We found no study mapping mold growth against water activity on cannabis flower itself.

Burping: A Taper That Follows the Reading

Burping, opening the jar to let humid air out, has no controlled trial behind it: we found no peer-reviewed study comparing burped and sealed cures or measuring the air in a curing jar (searches to Oct 6, 2026; a new October 2026 curing paper by Robinson and Martynenko, in Food and Bioproducts Processing, could not be read). Opening may cost aroma, though no study separates opening from time: in Joy's cure of two high-CBD hemp cultivars, with lids off 30 minutes daily, monoterpenes (lighter aroma terpenes such as myrcene and limonene) fell 14% and 22% in two weeks.

Practitioner schedules taper: Rosenthal and Downs send sweating day-1 jars back to drying, burp frequently to day 7, daily from day 7 and two to four times a week from day 14; Jorge Cervantes (The Cannabis Encyclopedia, 2015) opens two to three times daily in week one, then once or twice weekly.

The most useful rule is Rosenthal and Downs' meter method, a practitioner rule without data (the book gives no temperature, reading interval or sensor accuracy, and its authors prefer room curing, calling sealed-container curing "not recommended"): burp at once whenever the jar reads 65%; as buds dry, humidity climbs slower and peaks lower. Their endpoint, "Once the humidity stops climbing above 55%, the bud has finished curing," is aw 0.55 (our arithmetic), the ASTM floor, so we borrow the trigger, not the finish line.

Two-Way Humidity Packs and the Jar Reading

Two-way packs release or absorb water to hold a jar near a rated RH. Per the makers' stated specs, Vivi Fresh (Boveda Inc.'s rebranded cannabis packs) is salts, water and a thickener, rated ±2%: 58% in half-ounce and ounce sizes, 62% in pound sizes (Vivi). Integra Boost is glycerin and water, 55% or 62% for cannabis, no tolerance stated (Integra); ASTM D8197 names only salt-based sachets. Vivi claims its 50–55% Vivi Cure pack (at or below the ASTM floor) does burping's job automatically in 10 days, publishing no data.

The closest independent check: Pepperdine University's Nielebeck and colleagues (2022, PLoS ONE) put Boveda 58% packs in 2-litre containers of tick tubes, not flower: 58.3% RH on average (range 54.9–64.2) over about five days of hourly records in a 30-day run, as an incubator cycled 20–30 °C. In a separate 30-hour test at a constant 25 °C, the pack settled 4.1 points from its label (about 62% on the paper's figure). Logger calibration was unreported, and salt references in the same setup read 0.5–9.1 points off, so pack and logger error can't be separated. We found no independent, calibrated test of any 55%, 58% or 62% pack; the only jar test with plant material we found was run by retailer GrowersHouse (2016), which sells both brands: one jar per brand, no meter calibration reported.

Packs aren't shown to replace drying (ASTM allows sachets only below aw 0.68) or restore aroma. A pack also pins the reading near its rating, hiding the rise that tells you to burp (our inference): add one once readings hold steady, or for storage.

When Is the Cure Done?

No study or standard defines a finished cure; ASTM D8197 is a storage band. Extension pages lean on moisture content, a lab measure: NC State Extension cures hemp to under 10% total moisture, when stems snap, giving no total duration. Our proxy, labelled as ours: with no humidity pack in the jar, three sealed overnight readings taken two to three days apart all land inside 58–62% and within about 2 points of each other. That 2-point "steady" is ours; it tracks the trend, not the true value, which a meter rated ±1.5–3% can't give. If you added a pack because the jar read below 55%, the test no longer works; use the cues below.

Practitioner cues: at day 21, Rosenthal and Downs look for chlorophyll odours gone (their term; we found no study identifying the compounds behind a hay or grassy smell, or showing curing removes them), buds dry from surface to stem and a squeeze that springs back like a sponge; their small-scale room cure adds stems that snap cleanly while the bud stays pliable. Cervantes expects fresh, firm, pliable buds at 2–3 weeks.

Cure Length: What Books and Studies Used

None compared cure lengths; each research cure was a method choice. "Two weeks minimum, four to eight typical" is grower and vendor consensus; no study shows a longer cure improving anything, before or after the eight weeks Green praises.

What Curing Measurably Changes

Two studies measured the cure itself, both on high-CBD hemp:

• Baek, Grab and Chen: total cannabinoids didn't change significantly; about 1.0–1.8% of the CBD acid became neutral CBD in ambient-air- and freeze-dried samples, while hot-air-dried samples stayed near the 8–9% their 75 °C dry produced. Colour changed mostly in drying. Container RH sat at 17–31%, no model of a 58–62% jar.
• Joy: moisture ended lower than it started (10.0% to 9.1% and 12.0% to 11.2%, dipping by day 7 and rising slightly by day 14; no significance test), which Joy reads as unfinished equilibration; colour, measured on one cultivar, barely moved after the dry; monoterpenes fell (above).

In Oswald and colleagues' 2021 study (four plants; authors at terpene company Abstrax), skunky sulfur volatiles peaked as an 11-day hang ended, then all but one fell substantially within 10 days in mason jars. So in the studies we have, moisture keeps shifting in the jar and most measured aroma compounds fall, some within days; none shows the jar adding aroma.

The chlorophyll-to-sugar-to-harsh-smoke story has no cannabis measurement behind it: it traces to an uncited sentence in a 2021 review by Lazarjani and colleagues, extended by Das and colleagues in 2022.

The often-cited "best cure" (18 °C, 60% RH, 14 days, lid opened after six hours) is a citation-chain misquote: Caplan's thesis held flower at 18 °C and 60% RH for 14 days before weighing yield, with no lid timing; Jin and colleagues (2019) restated it, and later papers (Lazarjani, Das, Baek) made it the "best" cure and added Green's lid tip.

Temperature, Darkness and Bad Smells

• 60–70 °F is practice. We found no controlled comparison of cure temperatures. Rosenthal and Downs cure rooms at 65–70 °F, pack maker Vivi's blog (vendor) gives 60–65 °F with no source, and research cures ran 18–25 °C (64–77 °F). Over months of storage, cooler slows cannabinoid-acid loss (Meija and colleagues, 2022: ground, already-aged reference material kept dark at −20 to 40 °C for up to a year).
• Darkness has direct support: Fairbairn, Liebmann and Rowan (1976) (abstract only) found light (not direct sun) the greatest single factor in cannabinoid loss, especially in solutions.
• Ammonia or sour (house rule): treat the jar as too wet; we found no study measuring ammonia or other gases in curing jars. Inspect the densest buds, return clean ones to the drying space for a day, and re-jar at 58–62%.
• Musty, fuzzy or webbed: McPartland (1994) recorded growers screening for mold by a stale or musty smell and white-to-grey strands that turn fuzzy, with no validation cited. We found no validated home look-or-smell mold check, and spores on trichome heads show only under magnification (Gwinn and colleagues, 2023), so clean-looking isn't proof. Keep suspect buds out of use: see bud rot and mold.

FAQ

What humidity should you cure weed at?

58–62% RH, read in a sealed jar with no humidity pack after it sits overnight, inside ASTM D8197's 0.55–0.65 water-activity band. On the first night in the jar, above 62% means the dry isn't finished. After that, burp above 62%; still above 65% next morning, or above 68% at any point, means more drying.

How often should you burp curing jars?

No controlled trial sets a schedule. Common practice is a few minutes daily in week one; our rule adds an evening burp if the morning reading topped 62%. After week one, burp only above 62%, always at 65%; leave 58–62% jars sealed, reading every two or three days, then weekly.

How do you know when weed is done curing?

No study defines it. Our proxy: with no humidity pack inside, three sealed overnight readings, two to three days apart, all land at 58–62% and within about 2 points of each other. Rosenthal and Downs expect jars ready around day 21.

Do humidity packs replace burping?

Not while you're judging the cure: a pack holds the jar near its rating and hides the rise that tells you to burp, so add one once readings hold steady, or for storage. Vivi says its Vivi Cure pack makes burping unnecessary but publishes no data; we found no independent, calibrated test of any 55%, 58% or 62% pack, and no study shows packs restoring lost aroma.