The Science Behind Optimal Cannabis Cultivation revealed: Unveiling the Truth About Drying and Preservation Techniques
*preface - I am not the original author of this article. I simply communicate with him on a regular basis, find him to be extremely knowledgeable and wanted to preserve it for all people on this site. All credit goes to - @SharkMouseTheSecond -IG
the flaws in conventional wisdom-
In a groundbreaking exposé, The Deep End brings to light the hidden secrets of cannabis cultivation that could revolutionize the industry. Through meticulous research and analysis, a team of experts uncovers the flaws in conventional wisdom and presents a precision driven approach to maximizing the quality of cannabis products.
The Post Harvest Conundrum: Decades of Trial and Error Unraveled
The area for the largest potential improvement in your cultivation remains the post harvest process. The practices we as growers have adopted evolved from decades of trial and error experience that aimed to achieve 2 main goals: secondary metabolite and volatile compound preservation, and safe storage conditions. Nearly all of the steps in the workflow we’ve employed to get there are based off anecdotal logic. Some of that logic still holds value. Some of it deserves a much closer look.
Drying your fresh flower in conditions around the 60f/60% “low and slow” range, is based on the idea that drying flower at lower temperatures and lower vapor pressure deficits slows the rate of evaporation, helping prevent the flower from reaching its dry target before compounds like chlorophyll, sugars and other unwanted byproducts have had time to degrade. The logic also contends that lower temperatures may help reduce volatilization and oxidation of delicate volatile compounds during the drying process.
Combined with the widely cited relationship between equilibrium relative humidity and water activity:
aw = ERH/100
where ERH is equilibrium relative humidity, the logic behind “60/60” appears intuitive. A water activity around 0.64 is generally considered a safer storage threshold for limiting microbial proliferation while still maintaining acceptable texture and consumption characteristics.
The problem isnt that 60/60 is “wrong.” The problem is that drying dynamics are significantly more complex than static room temperature and humidity targets alone.
According to Fick’s first law, diffusive movement is proportional to the concentration gradient across a material. Moisture tends to move from regions of higher concentration toward regions of lower concentration.
J = -D(dC/dx)
In harvested flower, the outer surface layers lose moisture to the surrounding atmosphere first. As those outer tissues dry, moisture from deeper within the flower continues diffusing outward toward the surface. However, as drying progresses, the pathway resistance for that internal moisture movement increases. The flower is no longer uniformly hydrated. Surface tissues will become significantly drier while internal tissue still contains elevated moisture.
If you’ve ever run the “low and slow” method, you’ll probably recognize this phenomenon. After only a couple days, the flower feels dry on the outside. Several days later, that same flower can suddenly feel moist again as internal moisture continues redistributing toward the surface.
This creates two important considerations.
The first is microbial risk.
Dense inflorescences can retain substantial internal moisture even while external tissues feel relatively dry. Extended drying durations with unresolved internal moisture gradients increase the opportunity for microbial proliferation, particularly in uncontrolled environments with inconsistent airflow, temperature or humidity.
This doesnt mean every slow dried flower is “moldy,” or that microbial contamination is guaranteed. Microbial presence exists on all agricultural material to some extent. But, prolonged time spent in intermediate moisture conditions can increase contamination risk, especially in dense flowers where internal moisture migration happens slowly.
This becomes even more important considering how microbial testing standards work. A flower might visually appear clean while still carrying elevated microbial loads that aren’t visible to the naked eye.
The second issue involves volatile compound preservation itself.
Remember how we discussed moisture movement gradients? Surface tissues see the greatest exposure to oxygen and evaporative drying forces first. If the outer layers stay dehydrated for extended periods while internal moisture slowly redistributes outward, those tissues now spend prolonged periods exposed to oxidative degradation and volatile loss.
Does cooler temperature help mitigate volatilization? To a degree, yes. Lower temperatures generally reduce vapor pressure and can slow the evaporation rate of volatile compounds. But temperature is only one variable in the equation.
Once the plant is harvested, terpene and volatile compound concentrations trend down over time, not up. Heat, oxygen, light exposure and time most of all contribute to degradation.
The behaviour of individual terpenes was analyzed across multiple drying conditions and temperatures:
**The behaviour of individual terpenes was
analysed and were grouped based on their evaporation behavior against drying temperature.
Terpenes such as caryophyllene oxide (average content among all the drying conditions is 0.16%
or 1.6 mg/g; standard deviation- 0.01%) , sabinene (0.01%; SD- 0.001%), and α-terpinene
(0.002%; SD- 0.0002%), ocimene (0.001%; SD- 0.0001%), α-humulene (0.001%; SD- 0.0001%)
were decreased with drying but stable with the increase of drying temperature. Terpenes such as,
myrcene (0.006%; SD- 0.0005%), terpinolene (0.006%; SD- 0.0002%), α-pinene (0.02%; SD-
0.002%) and β-caryophillene (0.03%; SD- 0.001%) decreased gradually with the increase of
temperature. Terpenes such as, Guaiol, Nerlidol, g-terpinene, geranyl acetate, p-cymene, linalool
were almost completely evaporated with drying, leading to a significant decrease. All the
remaining terpenes that were analysed were not observed in fresh hemp samples itself.**
List of 12 Major terpenes observed in the hemp buds and their content at various drying conditions (mg/g)
the relative rate at which terpene concentrations changed across the tested drying conditions.
What becomes especially important in these findings is not simply that air temperature affects terpene retention, but the relative rate at which terpene concentrations changed across the tested drying conditions.
Using β-caryophyllene as an example, samples dried at 25 degrees celsius versus 32 degrees celsius showed a relatively modest difference in final concentration compared to the substantially larger terpene reductions observed across prolonged storage durations in other studies.
Ross and ElSohly measured “31.0, 44.8, and 55.2% loss of terpene content in Cannabis sativa inflorescence which had been air dried and stored for 1 week, 1 month, and 3 months, respectively, as compared to freshly harvested inflorescence” (Ross and ElSohly 1996).
Further work from The Preservation and Augmentation of Volatile Terpenes in Cannabis Inflorescence (2020) similarly demonstrated that “A more comprehensive analysis of 37 major terpenoids (of the 93 terpenoids analyzed) revealed the same general trend as α-pinene and β-caryophyllene; in other words, decreasing concentrations over time for all storage conditions.”
This does not suggest that drying temperature is irrelevant. Higher temperatures still accelerate many degradation and volatilization processes. However, the available literature strongly suggests that prolonged exposure time itself is also a major contributor to terpene decline following harvest.
All of this points toward a larger concept.
The Larger Concept -
The longer harvested flower stays suspended in unstable post harvest conditions, the more opportunity exists for degradation processes to occur.
How does any of this matter?
“We need two weeks to degrade chlorophyll for smooth smoke.”
This idea probably started from the observation that rapidly dried flower can develop grassy or hay like characteristics. While chlorophyll degradation likely plays a role in overall post harvest finish, the relationship is probably more complicated than chlorophyll content alone, as fresh cut plant material contains a range of volatile compounds, aldehydes, alcohols and degradation products associated with green plant aroma. Moisture content, combustion characteristics, drying conditions, oxygen exposure and degradation kinetics all likely heavily contribute to the final nose.
Darkness may also heavily influence post harvest degradation processes.
Effects of Light on Degradation of Chlorophyll and Proteins During Senescence of Detached Rice Leaves demonstrated accelerated chlorophyll degradation in detached leaf tissue kept under dark conditions. While detached rice leaves are obviously not identical to flowers, the findings suggest that darkness may help facilitate senescence associated degradation pathways in harvested plant tissue.
The goal here isnt to claim that cannabis flowers behave identically to detached rice leaves. But it does demonstrate that chlorophyll degradation can occur relatively rapidly under dark conditions in detached plant tissue.
How can we apply this knowledge toward achieving a better dry?
Using available drying kinetics literature, moisture desorption models and practical observations from controlled drying environments, we can formulate a stepped drying strategy intended to better balance moisture migration, volatile preservation and microbial management.
The goal isnt just to dry as cold as possible or as slow as possible.
The goal is to dry under conditions that hold a relatively controlled and continuous rate of moisture migration throughout the flower while minimizing unnecessary time spent in unstable moisture ranges.
If vapor pressure deficit remains too low for too long, drying becomes excessively prolonged. If vapor pressure deficit becomes too aggressive too quickly, surface tissues dry substantially faster than internal tissues, increasing the moisture imbalance across the flower.
A staged drying method gradually adjusts environmental conditions as the flower transitions through different phases of moisture loss.
My proposed framework for this process is as follows:
The sharkmouse method-
Phase 1:
72f or 22.2c at 55% rh for approximately 48 hours to begin removing surface moisture while still maintaining relatively controlled moisture migration from inner tissues toward the surface.
Phase 2:
74f or 23.3c at approximately 52% rh for approximately 24 hours to slightly increase vpd, promoting continued moisture movement while avoiding excessively rapid surface dehydration.
Phase 3:
75f or 23.9c at approximately 50% rh for approximately 48 hours.
The final phase continues reducing remaining moisture content while minimizing unnecessary additional drying time.
This framework isnt presented as an absolute universal optimum.
Different cultivars, flower densities, harvest conditions and environmental control systems may respond differently. This SOP represents a mechanistically reasoned drying model built on drying kinetics, moisture diffusion principles and volatile degradation literature.
Under controlled conditions, this approach may allow flower to reach stable storage moisture levels in substantially less time than conventional low and slow methods, reducing cumulative degradation exposure during the drying phase.
Remember when we discussed aw = ERH/100?
The purpose of drying isnt to hold flower indefinitely at equilibrium during unstable moisture conditions.
The goal is to safely and consistently move flower toward a stable storage state while preserving as much of the desirable profile as possible.
While much of this might instinctively seem counterintuitive to traditional drying logic, it makes more sense when we view it through the context of moisture kinetics, degradation exposure time and post harvest stability.
The sooner we can safely move harvested flower out of unstable transitional moisture conditions into stable storage conditions, the less chance exists for cumulative degradation processes to happen.
Resources-
Water Activity (aw) in Foods | FDA .
https://pubs.acs.org/doi/10.1021/np960004a
https://academic.oup.com/pcp/article-abstract/33/8/1183/1860636?redirectedFrom=fulltext
Particularly about how aroma changes from harvest to final storage, and beyond…
– WTH?! LOL
