Master the Art of Drying and Curing Cannabis

Columns - Tomorrow in Cannabis

Large commercial amounts of cannabis require special attention to every detail to ensure the resulting product is superior in quality.

February 4, 2020

Photo at Virtual Las Vegas by Mel Frank

Editor’s Note: This article first appeared in the April 2017 issue of Cannabis Business Times. Ken Morrow has been a featured columnist since the publication’s first issue. This article is the second most-read story in CBT’s five-year history.

One of the first questions I ask a potential consulting client is, “Do you and your employees purchase and consume the cannabis you produce? And if so, are you proud of the products you produce?” The answers I get sometimes surprise me, especially when the answer is “no” and that it does not matter because their products sell, regardless. At those times, I politely decline the employment opportunity. At no time in my career have I had any desire to produce anything other than the absolute best-quality cannabis possible with the funding and situation presented. I always strive to do the best I can with what I have.

A Colorado grower had once asked me to do a facility evaluation because their production totals were getting lower and lower each month. I began my assessment with a quick tour of the facility, then re-walked the facility without management, which allowed me to interview staff about their thoughts as to why production was slipping. Each employee sheepishly explained that management did not listen to the input or the needs of the employees, and that management told the grower that the plan was dictated by costs. Two out of three members of management never consumed cannabis, and it was simply a commodity to them. They were more concerned with the completion of their dispensary remodel than with the quality of their cannabis.

At one point, I attempted to explain to the carpenter/owner that no healthy cannabis plant is completely yellow and that he had 200 yellow plants. He would not even entertain me to go look at them.

At the same facility, another owner walked me to their drying room. As soon as they opened the door, I was blasted with the overwhelming odor of ammonia, a byproduct of degradation caused by inadequate airflow and by placing freshly cut product in the same environment with material that was almost dry. This essentially rehydrates the almost-dry material and does not properly address the humidity levels. Freshly cut material cannot be placed in the same room with material that has been drying for multiple days and be expected to dry at a uniform rate without proper ventilation, humidity and temperature control.

Yet again, these owners did not care because the product still sold. The one owner who did consume cannabis, as well as all their employees who were consumers, did not consume the cannabis they produce, nor were they proud of the product they sell.

A Phoenix, Ariz., operation was so focused on filling up its 65,000-square-foot facility to make money that it completely neglected to construct a proper drying and curing area. The management didn't understand or care about the importance of drying and curing. After three years of operation, their head grower quit. They couldn't sell all the mid-grade product at their two dispensaries, so they were forced to wholesale the majority of what they grow to competing dispensaries.

They do not grow quality cannabis, and theirs is certainly not a product to be proud of. When competitors produce superior products for a superior price, a company built on inferior cannabis will ultimately implode. You can grow the best, strongest, most aromatic cannabis in the world, only to destroy most of those qualities with improper drying and curing.

The Art of Drying and Curing

A bud of cannabis should have some give-and-take to it when squeezed, similar to the give-and-take when squeezing a marshmallow between thumb and forefinger. The bud should not be so dry that it simply crumbles or turns to a dry powder.
Photo at Virtual Las Vegas by Mel Frank

Drying and curing cannabis properly is an art in itself. Similarly, a tobacco farmer who grows tobacco for the finest hand-rolled cigars gives the highest level of care and attention to detail when drying and curing, which sets the stage for the final product. I have been to organic tobacco farms on a Caribbean island that dry and cure their leaves by old-world standards, the same as they have for decades. The care and the attention to detail they demonstrate is all for the love of the art, not just for monetary gain.

In the California, Oregon or Washington state coastal regions, it is very difficult to rapidly dry or over-dry cannabis because of the marine layer influence, which causes elevated nighttime humidity and, in some areas, fog. It is this marine layer influence that is responsible for mold and/or mildew proliferation in some cannabis. To rapidly dry or over-dry cannabis in these regions, one would have to try in fall and winter.

This is not so in some areas of Nevada, Arizona or Colorado, two of which have significant differences in elevation, temperatures and humidity variation. Arizona and Nevada are both different climates that can range from 115°F in summer to 28°F and lower in winter, with low humidity levels most of the year and no real humidity influence except for monsoon season in Arizona.

Denver, Colo., is more than 5,000 feet in elevation and in many areas, elevation is even higher, and temperatures can range from sub-0°F in winter to well over 100°F in summer. In winter, in one 24-hour period, it can range from subzero and snowing with 0-percent humidity at night to 75°F with 60-percent humidity during the midday as the snow melts in the sunshine. Both of these diverse climates require special attention to drying and curing, which may not be required in a region that has a predictable coastal marine layer influence.

A bud of cannabis should have some give-and-take to it when squeezed, similar to the give-and-take when squeezing a marshmallow between thumb and forefinger. The bud should not be so dry that it simply crumbles or turns to a dry powder. Rapidly dried or over-dried cannabis, as mentioned, has diminished levels of desirable terpenes and is much less flavorful than properly dried and cured cannabis. Small amounts of cannabis are fairly simple to dry and cure, as long as you understand the nuances and maintain a stable proper environment that is not too hot nor too cold, in a well-ventilated area.

Columnist Kenneth Morrow explained to a client in Arizona that they must seal their environment; their solution was to attempt to seal roll up bay doors with cans of spray foam, which immediately fell off.
Photo courtesy of Ken Morrow

However, large commercial amounts of cannabis require special attention to every detail to ensure the resulting product is superior in quality, not over-dried and flavorless. Many believe that with properly dried and cured cannabis buds, the primary stem inside the body should be so dry that it snaps in half when bent. In reality, that would be considered over-dried. It should crack, yet bend without being wet or excessively moist. Again, the stem should audibly crack, but not break in half, and the bud should have give-and-take, not explode into powder.

It is a fine line. Drying and curing are developed skills that come from actually consuming the cannabis you produce (if you are a medical patient or involved in an adult use business) and striving to always make it better. Yet again, it is an art as well. There is no magic temperature and humidity set point, because there are many variables from seasonal temperatures, fluctuating humidity levels, elevations, barometric pressures, different cultivars and quantities, and so on.

However, a drying room should always be properly ventilated, with fresh, filtered, outside air and with proper odor control practices on all exhausted air. It should have the ability to both impart humidity via a humidifier and to dehumidify via a dehumidifier, as well as the ability to both heat and cool. Whether you hang dry individual plants or branches with buds attached or put wet, trimmed buds on racked screens, whether your crop is 500 pounds or 50,000 pounds, you must have at least that amount of control over the drying rate—not excessively hot (over 75°F to 80°F). Many dry at lower temperatures, for example, 60°F to 70°F, to preserve the highest percentage of terpenes possible.

Temperatures that are too cold, however, with improper airflow, will produce inferior cannabis with undesirable qualities; the final product retains excessive levels of chlorophyll, and never smells or tastes as it should, and sometimes has a fresh cut grass or hay odor. Humidity control is always a must. Logically, one would want to eliminate as much humidity as rapidly as possible, which is typically accelerated with elevated temperatures. But there is a fine line between rapidly drying the cannabis and rapidly evaporating terpenes, contained inside the trichomes that coat the outside of the cannabis buds.

Each and every terpene has a boiling point and temperature at which it begins to evaporate. Monoterpenes evaporate first and are typically the primary terpenes evaporated in drying. The task is to eliminate unwanted moisture from the plants and buds as rapidly as possible without evaporating excessive amounts of terpenes. The outside of the bud dries first and becomes slightly dry to the touch.

The art is to draw the inner core humidity to the outside slowly, without sacrificing terpenes. The cigar tobacco-leaf drying sheds on the Caribbean island had ropes hanging from the ceiling. Bundles of leaves were raised or lowered from the floor to the 20-foot ceiling multiple times a day to accommodate proper drying and curing, because the higher you go in the shed, the hotter and more humid the air. Take note, this is in the Caribbean on an archipelago in the Atlantic Ocean with a hurricane season.

No healthy cannabis plants are yellow, and starting off with unhealthy plants not only suggests a lack of concern for product quality, but also is going to lead to poor-quality cannabis once it's dried and cured.
Photo courtesy of Ken Morrow

Heaters, coolers, humidifiers and dehumidifiers combined with airflow are the science if used properly, but there must be “the art” in the equation as well. Someone who does not appreciate the nuances of cannabis and all its qualities, whether they personally consume cannabis or not, should not be in charge of drying and curing.

When the outside of the plant is dry, it is best to rehydrate the outside of the bud by drawing the inside moisture to it. The best way to achieve this is to place the buds into a sealed container for a short period at drying temperature (for 2 to 24 hours depending on quantity), while periodically exchanging the container air. The bud will again become uniform in moisture consistency or dryness. This can be very time-consuming and difficult at large-scale, which is why few large-scale commercial growers do it. The homogenized buds are then rehung or placed back on drying racks to repeat the process until the desired moisture content is achieved, which should never be “very dry.”

This begins the curing phase. Always be careful to avoid excessive temperatures and be vigilant for any possible signs of mold. If there is any mold present, it will spread in a warm, moist environment, which is exactly what you don't want. Properly dried cannabis is fairly easy to cure. After proper drying, the cannabis is again placed into sealed containers to prevent moisture and terpene dissipation. The sealed containers are checked multiple times a day, and all air in the container is exchanged for fresh air.

At this point, proper moisture content is closely monitored. If a container is opened and the buds are excessively moist, the container is left open until desired moisture content is achieved, or the contents can be placed on the drying rack and closely monitored.

This process is repeated over and over and over again until the perfect, uniform, desired humidity and moisture content are achieved. And therein lies the art.

About the Author: Kenneth Morrow is an author and writer who has been covering cannabis-related subjects for more than 20 years. He is the owner of Trichome Technologies, a cannabis research and development company. Morrow also is an award-winning grower and breeder. He has made contributions to many of today's extraction methodologies and holds multiple patents in the field. He currently specializes in product formulation and consults on all cannabis-related subjects. Find him on Instagram (TrichomeTechnologies) or Facebook (Trichome Technologies).