A grow can be technically perfect — optimal VPD values, precise EC curves, a clean harvest — and still fail in the final phase. Drying and curing are not the conclusion of the grow. They are an independent process phase with their own parameters, their own failure modes and direct influence on the end product.
Dry too fast and you lose terpenes through evaporation. Cure incorrectly and chlorophyll and unwanted compounds are not broken down. Get both wrong and you harvest grass — not cannabis.
The biochemistry behind curing — what actually happens
Freshly harvested cannabis still contains active enzymes and living cells. In the first days after harvest, breakdown processes continue: chlorophyll is broken down by enzymes, simple sugars are metabolised by microorganisms and enzymes, and the carboxylic acid forms of cannabinoids (THCA) slowly continue to convert.
Curing is controlled enzymatic decomposition at low moisture content. The goal: break down chlorophyll and plant sugars (responsible for the "green", harsh smoke) without losing terpenes and cannabinoids. This balance depends on temperature and humidity.
What should be preserved: terpenes, THCA/CBDA, complex phenols, flavonoids
What can be destroyed (to be avoided): terpenes through heat, cannabinoids through light and oxidation
Phase 1 — drying: slow and controlled
The drying phase aims to reduce the water content of the flowers from approximately 75–80% to 10–15%. The speed is decisive.
Too fast (< 5 days): the outside dries out, the inside remains wet. Terpenes evaporate through the broken outer shell. Chlorophyll is not fully broken down. Result: a harsh, bitter smoking experience despite good flower quality.
Too slow (> 14 days without control): mould risk rises drastically above 65% relative humidity in combination with organic material. Botrytis needs no visible conditions — it grows inside dense flowers.
Optimal: 7–14 days under controlled conditions.
| Parameter | Drying target | Effect when deviating |
|---|---|---|
| Temperature | 18–22 °C | > 25 °C: terpene loss through evaporation |
| Humidity | 45–55 % RH | > 65 %: mould risk · < 35 %: too fast |
| Air circulation | Gentle, indirect | Direct draught dries unevenly |
| Light | Dark | UV degrades cannabinoids (THCA → THC → CBN) |
| Hanging | Upside down on branches | Lying flat: pressure points, uneven drying |
The dry test — when is phase 1 complete
The classic test: bend the branch at the thinnest point. Does it snap cleanly with a quiet crack — phase 1 drying complete. Does it bend elastically — too wet. Does it break instantly into dust — too dry (dried too fast).
More precise: a hygrometer in a closed container with a sample of the flowers. Target value after 24 hours: 58–62 % RH inside the container. That corresponds to an internal water content of the flowers of approximately 10–13 %.
Phase 2 — curing: the actual refinement process
Curing takes place in airtight sealed containers — traditionally glass jars with rubber gaskets. The principle: residual moisture inside the flowers diffuses evenly outward (diffusion). Enzymatic processes run in a controlled manner at low oxygen content.
Burping — why and how often
"Burping" means: open jars daily, let in fresh air, close again. In the first two weeks daily for 5–15 minutes. Purpose: release CO₂ and moisture from the container, let in fresh oxygen for the enzymatic processes.
If a strong ammonia or moisture smell appears on opening: the flowers are still too wet. Leave the lid slightly open longer, then continue curing. If it smells of mould: check immediately and remove affected flowers.
| Curing duration | Expected result | Burping frequency |
|---|---|---|
| 1–2 weeks | Basic quality · noticeably better than fresh | Daily |
| 3–4 weeks | Good quality · aromas develop | Daily → every 2 days |
| 6–8 weeks | Very good quality · complex aroma profile | Every 3–5 days |
| 3–6 months | Excellent quality · maximum terpene development | Weekly |
| > 6 months | Diminishing returns · THCA degrades to CBN | Monthly or seal |
Optimal curing conditions
| Parameter | Target value | Why |
|---|---|---|
| Temperature | 18–21 °C | Enzymatic activity without terpene evaporation |
| Humidity in jar | 58–62 % RH | Enzymatic processes active · prevents mould |
| Light | Complete darkness | UV protection · no cannabinoid degradation |
| Container | Glass · UV-protected · airtight | No absorption of odours / foreign substances |
| Fill level | 75–80 % of container | Enough air space for gas exchange when burping |
Boveda packs — useful or not
Boveda packs (62 % or 58 %) are two-way humidity regulators based on salts. They release moisture when the inside of the jar gets too dry, and absorb moisture when it is too wet. Practical for long-term storage and for growers who cannot burp daily.
To be viewed critically: Boveda packs do not replace phase 1 drying. Whoever seals overly wet flowers with a 62 % pack preserves the moisture instead of breaking it down. Order: dry correctly first, then use Boveda for stabilisation.
Common mistakes — and their symptoms
| Mistake | Symptom | Solution |
|---|---|---|
| Dried too fast | Harsh smoking experience, hardly any aroma, coughing | Longer curing can partially compensate |
| Stored too wet | Ammonia smell, mould in jar | Open immediately, dry, inspect |
| Light during curing | Accelerated cannabinoid degradation | Dark storage — always |
| Too high temperature | Terpene loss, "flat" smell | Store below 21 °C |
| No burping | CO₂ build-up, mould risk, stagnant enzymes | Open daily in the first 2 weeks |