After flower has dried slowly and passes the stem-snap test, curing it in sealed jars finishes the job. This part explains what happens inside the jar, how often to open it and what humidity packs can and cannot do. It also covers what Thailand’s climate demands from a drying room and ends with a day-by-day protocol from harvest to storage.
This part uses two terms from Part 1. Water activity (aw) shows how much of the water in the flower is free to feed mould. It is a number from 0 to 1. The industry standard ASTM D8197-22 sets the target for dry flower at aw 0.55–0.65. The stem-snap test checks whether drying is finished. Bend a small stem: if it snaps cleanly instead of bending, the flower is ready for jars.
This is Part 2. Part 1: Drying & Curing: The Science of Not Ruining Your Harvest
What happens inside the jar
Flower is ready for jars once it reaches aw 0.55–0.65 and passes the stem-snap test. Grower communities often describe curing as something mysterious. In fact, the chemistry behind it is well understood.
Enzymes keep working. Enzymes still work after part of the water is gone. The enzymes that break down chlorophyll keep going. Enzymes from the living plant also keep slowly breaking down the leftover sugars.
Slow browning reactions. Well-cured flower gets its deep aromas partly from reactions between amino acids and sugars at low temperature. These reactions are related to the Maillard reaction, the browning that gives toasted bread or grilled meat its colour and smell. The full Maillard reaction usually needs higher temperatures. In the jar, related but slower reactions take place instead (condensation and oxidation chemistry).
Terpenes spread out and settle. During the cure, the aroma compounds move through the flower and become stable. This is the main reason why freshly dried flower, which can smell sharp, green or flat, develops a rounder, fuller aroma.
Oxygen helps, but too much does harm. Opening the jar (“burping”) lets out carbon dioxide produced by microbes. It also lets in fresh oxygen for the enzymes. Too much oxygen, however, speeds up the oxidation of cannabinoids. You keep the balance by opening the jar only for short periods.
Translator’s note: the original article says glass jars are the only acceptable curing container, except for bulk commercial storage. It gives no reason for this. We found no published study that compares glass with food-grade plastic or metal for curing. Glass does not react with the flower, and a tight seal matters as much as the material. One clear practical advantage of glass is that you can see condensation or mould without opening the jar.
What to do: use airtight glass jars. Label each jar with the harvest date and the jarring date so that you can follow the schedule below.
Burping schedule
The day numbers in this table count from the day you seal the jars.
| Cure days | How often | How long to open |
|---|---|---|
| 1–7 | 2–3 times a day | 10–15 minutes each time |
| 8–14 | Once a day | 10 minutes |
| 15–21 | Every 2–3 days | 5–10 minutes |
| 22–30 | Once a week | 5 minutes |
| After 30 | Once a month or less | 5 minutes, and sniff for off-odours |
During the cure, the air inside the jar should stay at 58–62% relative humidity (RH).
Translator’s note: to check the humidity inside the jar, put a small digital hygrometer (humidity meter) into one jar from each batch. Take the reading before you open the jar. A reading of 58–62% means the cure is on track. Above 65% means the flower is still too wet (see condensation below). Below 55% means the flower is too dry, so keep the jar closed and consider a humidity pack. These limits use the rule of thumb from Part 1 that jar RH divided by 100 roughly equals aw.
Translator’s note: in Thailand, open your jars inside the air-conditioned room, not outdoors or in a humid kitchen. If air at 80–90% RH gets into the jar, burping adds water instead of removing it.
Ammonia smell when you open the jar. Bacteria that live without oxygen are growing in the jar. The flower was too wet when you sealed it. Spread the flower on a clean surface and let it dry further before you put it back into jars.
Condensation on the inside of the lid. The flower went into the jar with water activity still above 0.65. Open all the jars. Let the flower dry for another 24–48 hours at 50–55% RH, then seal the jars again.
What to do: set phone reminders for burping, and write down the jar hygrometer reading each time. The record shows whether each batch is drying out or staying too wet.
Humidity packs: what they can and cannot do
Boveda, Integra and similar products are two-way humidity packs. They absorb moisture when the jar is above their set RH and release moisture when it is below. The 58% and 62% packs are the most common for curing and storing cannabis.
The packs contain calibrated saturated salt solutions. A saturated salt solution keeps a constant vapour pressure, so the air above it stays at a constant RH. This physics has been known for more than a century, so the technology is reliable.
A pack cannot save flower that went into the jar too wet. It can only hold RH within a narrow range. It cannot remove large amounts of water from wet flower. Dry the flower properly first, and then the pack keeps it at the right humidity.
Translator’s note: a pack keeps jar humidity steadier, which helps when you open and close jars in a humid climate. To buy them, ask the official distributor in Thailand, or ask about other growers’ experience in Equipment and Supplies. To start, put packs in a few jars from one batch. Then compare their hygrometer readings with jars that have no pack.
Drying in Thailand’s climate
Drying guides written for cool climates do not cover Thai conditions. In most of Thailand, outdoor RH runs from 65% to 90% through the rainy season (May–October). Temperatures commonly go above 32 °C all year round.
What this means in practice:
A dehumidifier is required, not optional. In the rainy season, flower air-dried in a room without climate control cannot get below aw 0.75. This is well above the mould limit of 0.65. At minimum, you need a purpose-built drying room with at least one commercial-grade dehumidifier and proper drainage for the collected water.
Air conditioning controls the temperature. When the air conditioning holds the room at 15–21 °C, it also removes moisture. In Thailand, this is a significant running cost that must be included in production costs.
The risk of grey mould is higher. Botrytis cinerea (grey mould) thrives at 17–23 °C and RH above 85%. If infected flowers enter a drying room, they can spread grey mould through the whole batch, even when they are dry on the surface. Inspect the flowers at harvest and keep any suspect material separate before drying.
The equipment costs more and takes longer to pay back. A drying room needs to be sealed and needs dehumidifiers, heating, ventilation and air-conditioning (HVAC) and airflow management. All of this costs more in tropical climates than in temperate ones. Commercial producers in Thailand should budget for it. Good genetics cannot make up for missing equipment.
Translator’s note: the original is written for commercial rooms. On a smaller scale the same logic applies. You might use a closet or small grow tent inside an air-conditioned room, plus a household dehumidifier. Add a small fan pointed away from the buds and hygrometers in two places. Fit the batch size to what your space can hold at 45–55% RH. The forum compares and costs five Thai setups for drying at 85–95% outdoor humidity in Drying Cannabis at 85–95% Ambient Humidity: Five Thai Setups, Costed and Ranked.
Translator’s note: power cuts are a real risk. When the air conditioner and dehumidifier stop, the room drifts toward the outdoor humidity. A data logger shows how long RH stayed high. After an outage, check the logger and inspect the buds in the middle of the racks. Do not rush flower into jars to “protect” it, because flower jarred too wet is at greater risk. If outages are common where you are, plan backup power for the dehumidifier and air conditioner.
Translator’s note: to find your real drying cost, plug the air conditioner and dehumidifier into a plug-in energy meter for one batch. Divide the kWh used by the dry weight of the batch. The result shows what drying costs you per kilogram.
What to do: test your empty drying space during the rainy season. This shows the worst conditions your equipment must handle.
Equipment for a drying room
Well-funded farms often produce much better flower than underfunded ones. The difference shows most clearly in the drying room. In a tropical climate, stable temperature, exact humidity, enough airflow and complete darkness never happen by accident.
Dehumidifier capacity
A rule of thumb in commercial drying is to size the dehumidifier by the batch’s fresh (wet) weight. Per day, it should be able to remove at least 10% of that weight, counted in litres of water.
Example: a 50 kg wet harvest might give 12–15 kg of dry flower. Over 7–10 days, it loses about 35–40 kg of water, roughly 4–5 litres per day. Humid air keeps entering the room, so you need extra capacity. This batch needs a dehumidifier rated for at least 6–8 litres per day.
In Thailand’s humid climate, choose a unit at least 50% larger than the size recommended for temperate climates. Dehumidifiers work harder and switch on more often in very humid air.
Translator’s note: for the 50 kg example above, 50% more capacity means a unit rated for about 9–12 litres per day.
Air conditioning
The right choice is a dedicated split-type air conditioner, with the indoor unit in the room and the compressor outside. A portable unit is the wrong choice because it blows hot air back into the same space it is cooling. The air conditioner’s cold indoor coil (the evaporator) also removes moisture from the air. This adds to the work of the dehumidifier.
Data-logging sensors
Consumer hygrometers with ±5% accuracy are not good enough for professional production. Industrial data loggers are much more accurate. Check the stated accuracy on the datasheet. Set them to record temperature and humidity every 15 minutes. You then have a record of each batch to check later. This record is useful for quality control and for compliance with regulations.
Translator’s note: the sensors show where your room is too wet and give you a record of each batch. If your farm is certified under Good Agricultural and Collection Practice (GACP) or is working toward it, see Good Agricultural and Collection Practice for Cannabis: Records, Farm Site, Crop and Drying (Part 1 of 2) for how drying records fit in. To start, place two or three loggers near the door, in the centre and in a corner during an empty-room test. Compare the readings.
Racks and hanging space
Hanging rails or wire-mesh drying nets should leave at least 15 cm of clear space between neighbouring buds or branches. Overcrowding cuts airflow and raises the humidity around the buds. Drying time also grows faster than the extra load. A rack overloaded by 30% may need 40–50% more drying time, and the risk of mould stays higher the whole time.
Sealed rooms
A drying room that shares air with the next room cannot reliably control its own conditions. Air can enter through gaps around doors, shared ducts or open windows. You must seal the room before you can hold the same conditions from batch to batch. Fit rubber sweeps along the bottom of the door and seal the holes around light fittings. The HVAC ducts must not share air with other spaces.
What to do: before your next harvest, check the room for gaps, count your rack space at 15 cm spacing and compare your dehumidifier’s rating with the size of your batch.
30-day or 60-day cure?
Many growers say that a 60-day cure gives clearly better flower than a 30-day cure. Published research describes the changes in the first two weeks of curing well. Much less is known about the chemistry in weeks three to eight.
Several things seem likely:
- Chlorophyll keeps breaking down slowly through the first several weeks.
- The slow browning reactions probably take weeks to months, not days. Other slow food processes, such as making wine or aged cheese, follow a similar timeline.
- In large, dense flowers, terpenes may need more than 30 days to spread evenly and become stable.
The way to check is a blind sensory evaluation, where testers do not know which sample is which. Compare a 30-day and a 60-day cure of the same cultivar grown under the same conditions. There is little published blind-test data from controlled settings. Experienced commercial quality assessors, however, consistently report that they can tell the difference.
For commercial farms, flower in storage ties up money, so a 30-day minimum cure is the practical standard. Small producers may be able to set aside a whole batch for a longer cure without pressure on cash flow. For them, a 60-day cure is justified by the better quality.
What to do: split your next batch into two sets of jars. Open one set at day 30 and the other at day 60, and compare them blind. You will learn whether the extra month is worth it for your cultivar.
Full protocol, day by day
Translator’s note: the original article’s tables counted days slightly differently. The table below counts from harvest day (day 0) and assumes you jar the flower on about day 10. The cure-day numbers in brackets match the burping schedule above. If you jar earlier or later, follow the cure days.
| Day from harvest | Stage | What you do | Conditions | What is happening in the flower |
|---|---|---|---|---|
| 0 | Harvest | Cut. Wet trim, or hang the whole plant | — | — |
| 0–1 | Hanging | Hang in the drying room | 20 °C, 50–52% RH, dark | — |
| 1–3 | Early drying | Check for mould daily | About 20 °C and 50% RH (range 18–20 °C, 47–52%) | Water evaporates fast from the surface. Chlorophyll begins to break down |
| 4–10 | Late drying | Keep checking for mould. Do the stem-snap test daily from about day 7. Jar when stems snap (usually day 7–10) | About 18 °C, 48–52% RH | Water moves out from the core. Stems stiffen. The terpene profile begins to settle |
| about 10–17 (cure days 1–7) | Early cure | Burp 2–3 times a day, 10–15 min | Jars at about 20 °C, 58–62% RH inside the jar | Enzymes finish their work. Slow browning reactions start |
| about 17–24 (cure days 8–14) | Early cure | Burp once a day, 10 min | Same | Same |
| about 24–31 (cure days 15–21) | Mid cure | Burp every 2–3 days, 5–10 min | Jars at 18–20 °C | Terpenes stabilise. The aroma becomes more complex |
| 30 | Minimum cure | Test aw if you can use a lab | aw 0.55–0.65 confirmed | Minimum standard for quality flower, enough for most uses |
| about 31–40 (cure days 22–30) | Mid cure | Burp once a week, 5 min | Jars at 18–20 °C | The aroma keeps developing |
| about 40–60 (after cure day 30) | Extended cure | Burp weekly to monthly, 5 min, and sniff for off-odours | Same | Harsh notes smooth out further |
| 60 | Extended cure complete | For premium product | Same | High-resin cultivars reach their best aroma and flavour |
| After 60 (90+ days) | Long-term storage | Move to storage | Dark, 15–18 °C, sealed | A cure of 90+ days helps some flower intended for hash making. Most flower gains little |
What to do: print this table and put it on the drying room door. Tick off each step for every batch.
Five rules to follow every time
- Dry slowly. For most cultivars in most conditions, allow at least seven days from cutting to jar.
- Aim for aw 0.55–0.65, not just a moisture-content percentage.
- Control temperature as carefully as humidity. Above 25 °C during drying, terpene loss gets measurably faster.
- Cure in glass jars. The original article accepts other containers only for bulk commercial storage.
- In Thailand, budget for a dehumidifier as a production cost. It is not an optional extra.
Shortcuts in drying are tempting, because every day in the drying room is another day before you can sell or use the harvest. But chlorophyll breakdown and terpene development happen only during this period. Time skipped in controlled drying cannot be made up later. Each step in the protocol has a specific chemical purpose. A shortcut at any stage causes faults that later steps cannot fix.
If you cure flower in Thailand or Southeast Asia, post your jar hygrometer readings and your burping schedule below this topic. Questions about a specific batch are welcome there too.
References
- ASTM International. D8197-22, Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower Intended for Human/Animal Use.