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Properly Drying and Curing Marijuana

Posted September 6th, 2017 by Ed Rosenthal in

Properly Grown, Dried and cured flowers burn smoothly and taste flavorful. The smell and flavor come from the terpenes and flavonoids in the buds. Terpenes also contribute to the strain’s specific effects. For buds to be proud of, think “low and slow.” Drying and curing flowers takes time and patience, but the finished buds are worth the wait.

”Low” refers to temperature. Terpenes evaporate at different tempera­tures, and some at slightly below room temperature. When the air is fragrant with flower odors, the buds are losing their terpenes. Improperly dried and cured buds lose terpenes due to evaporation.

For example, the terpene myrcene—found in mango fruit, hops, bay leaves, eucalyptus, lemongrass and cannabis—evaporates at just 68º F (20º C). In addition to contributing to the smell, myrcene has analgesic, antibac­terial, anti-inflammatory, anti-depressant and anti-anxiety properties and helps THC cross the blood/brain barrier. Terpenes are essential to cannabis consumers. Buds must be dried at low temperatures for the terpenes to be preserved. Drying at low temperatures and moderate humidity takes longer, hence “low and slow.”

Under cool conditions the plant’s cells stay alive for up to 72 hours after cutting. During the early part of drying, the plant consumes some of its store of water and carbohydrates. Dried too fast, the buds use fewer starches, resulting in a harsher smoke. Cells on the surface of the plant die first, and the ones farther inside die last. During the first stage of drying, water loss is rapid. At the same time some of the chlorophyll degrades, creating a smooth smoke. Buds dried slowly and then cured for a few weeks develop the smooth draw of fine herb. Rushed drying locks in chlorophyll leaving a “green,” minty taste and a rougher smoke.

Degraded THC

Heat and light degrade THC into cannabinol (CBN), which has only a frac­tion of the psychotropic effect and induces sleepiness. When buds, es­pecially large ones, are dried at high temperatures to speed the process, they dry unevenly. By the time the inner portion is dry, some of the THC on the outer portion has turned to CBN.

Small-Scale Drying

The drying needs of a small scale grower are the same as those of a large scale grower, but climate control is less of a challenge.

Climate-Controlled Drying Box

Find a climate-controlled drying box such as a grow tent, large appliance box, or construct one using wood and plastic or plasterboard walls. Add a hygrometer connected to a small dehumidifier and a thermostat regulating a heater or air conditioner.

Drying in a Bag

A brown paper bag is a simple way to keep humidity higher than the humidity in a room; this slows evaporation. Recirculate humidity by opening or closing the bag. To keep the humidity lower, place only two or three layers of big buds in the bag. Use a hygrometer to measure the moisture level in the bag. If the humidity climbs above 50%, use a fan to remove moisture-laden air.

Closed, Humidity-Neutral Space

A small room or a closet is likely to have the right temperature for drying. If not, adjust the conditions by opening or closing the door and using a fan. For more control, use a heater, air conditioner, humidifier, or dehumidifier as needed.

Rack Drying

The advantage of rack drying is that air flows freely around the buds. Using fans to circulate the air shortens drying time.

Not A Drying Space

Don’t dry buds in a room with growing plants because the conditions required for the two operations are incompatible. The humidity and tem­perature in the growing room are likely to be too high for proper drying. The result may be mold attacks and loss of terpenes through evaporation.

Never dry in jars or closed containers. Buds should neither be dried nor cured in an enclosed container such as a closed box, plastic container or jar that traps air. As the buds dry, humidity in the container builds up and water is likely to condense on the sidewalls of the container, increasing the ambient moisture. These are ideal conditions for mildews, molds and bacteria to thrive.

Mold and mildew are likely to attack in closed containers, causing rot (botrytis) and molds. The fungi and aerobic bacteria use up the oxygen and anaerobic bacteria, which thrive in a non-oxygen environment. Their telltale sign is the acrid odor of ammonia they emit.

Molds, mildews and bacteria have a devastating effect on the terpenes and flavonoids (taste molecules); infected marijuana loses its distinctive odors and smells earthier.

None of the conditions created by closed containers are good for buds. The microorganisms can quickly turn a good harvest into waste.

The concept of using a closed container for either drying or curing is an urban myth. People often “burp” (open) the jars during drying to remove excess humidity. However, the humidity is trapped until the burping takes place, encouraging the proliferation of molds.

Steps to Drying

Clean the Space to be Used for Drying

If it has been used for har­vests before, wipe it clean with a hydrogen peroxide solution or just spray the whole space using it. This decreases microorganisms on surfaces. To keep air free from mold spores, hang a UVC sterilizing light and set up a carbon filter to cleanse the air of odor, particu­lates and microorganisms.

Use an Air Conditioner and Heater

Maintain a temperature of about 68º F (20º C) in the drying area. Set the humidifier/dehumid­ifier to maintain humidity at 50%. When relative humidity is higher than 55%, the germination and growth of fungi and bacteria on wet material proliferates after about two or three days. Humidity be­low 45% promotes faster drying, but at that humidity level big buds have a tendency to dry on the outside while the inside remains `moist.

Use Fans

Turn on oscillating circulation fans to keep air moving throughout the space.

Hang the Buds

Add buds by hanging them or laying them on screens. Don’t flat-dry flower buds or branches on screens if intending to machine trim them. Gravity compresses the part of the bud touching the surface. Trimming machines don’t work well when fed flat-dried buds.

Monitor the Progress

Monitor the buds during the drying process. This process can last from one to three weeks. Bud size, crop weight, crop moisture, am­bient temperature and humidity all affect drying time.

Leave a Light On

Leave a dim light on throughout the drying process.

It is important to clean equipment in the drying room frequently because fungi and bacteria can colonize air conditioning units, humidifiers and de­humidifiers. Remove and clean the filter and spray the interior with a 3% hydrogen peroxide solution. Allow all parts to dry before reassembling.

When Drying is Complete

As the buds dry, they lose color and weight and become more brittle. The green color fades a bit as chlorophyll degrades, making yellow, brown, red and purple hues more prominent.

The first stage of drying is complete when buds feel dry on the outside but retain moisture inside that keeps them fairly pliable. Take an average-sized bud and slowly try to fold it in half. If the bud stem bends, the bud is still too wet. If the bud stem breaks, it’s ready to be cured. If it breaks with a crisp snap, it is ready to cure. Another way of subjectively judging readiness is by lighting up a thinly rolled joint. If it doesn’t go out between puffs, then it is ready for curing and storing.

Buds on cut whole plants take a longer time to dry than on cut branches and trimmed buds because there’s more vegetation and thus more water to evaporate. But the slower cure mellows the taste. Big, thick, dense buds take much longer to dry than smaller buds and are more susceptible to mold and powdery mildew.

Drying Outdoors

The main factors that affect outdoor drying are the same as indoors: temperature and humidity. However, dealing with these factors outdoors is more complicated because humidity and temperature vary over the course of a day. Starting in the morning at sunrise, the day begins to heat, drying any dew that set during the evening. Heat accumulates until midafternoon when the temperature drops, increasing relative humidity (RH) and the chance that dew will fall. Even in areas with small rises and drops, there may be danger during the hottest part of the day and then again as dew drips onto the plants. Keep plants away from the sun’s heating rays using white reflective material that bounces rather than absorbs the light.

In the Shade

Provided the ambient temperature and humidity stay in a moderate range—50-68° F (10-20° C) temperature and 40-55% humidity— plants can be dried outdoors. The evening humidity and temperature are critical. Moisture from dew promotes infections. An area exposed to dew is unsuitable for drying unless a dehumidifier to eliminate the moisture. Another possibility is to maintain temperature at 68° using a heater, so there is no increase in RH.

In a covered area with no sidewalls: An outdoor area that is covered and has no sidewalls is suitable for drying, provided the temperature and humidity stay within range. Fans may be needed to remove dew and to cut down on midday heat and morning humidity.

Quick Drying or Ways Not To Dry Buds

There are several methods to dry marijuana quickly for testing, but none will yield high-quality, well-dried, well-cured buds. However, fast-dried buds are an indication of what to expect once the rest of the harvest is dried. Fast-dried buds retain their minty chlorophyll taste and have a harsh smoke.

Place the buds in the microwave for 30 seconds or longer so some of the moisture is removed and then lower the power to 2 and dry the buds until dry enough to test. Microwaves kill seeds, so buds containing desired seeds should not be microwaved.

Food dehydrators fast-dry buds, but many of the terpenes evaporate in the elevated temperature. They never get very hot, so the THC remains but the flavors dissipate. This kills seeds.

Place the small bud on top of a warm appliance such as a computer or refrigerator.

Don’t try drying marijuana in an oven unless it has a very low setting. Even so, the heat may evaporate the terpenes before the buds are dried. Set the temperature at 100° F (38° C) if possible. This may kill seeds.

Rehydrating Over-Dried Buds

There are plenty of myths and old-fashioned methods for rehydrating over-dried buds. One calls for placing fresh flour tortillas or fruit in a sealed con­tainer with the buds so they can absorb the moisture from them. Using fresh fruit to rehydrate buds is unsanitary.

Either put the buds in a climate-controlled room with increased humid­ity, about 70%, or use a tea kettle to produce steam. Place the buds in a Rub­bermaid container, add a little steam and close the lid tightly. Leave the steam in the container for a couple of hours. Check the buds to determine if they are remoistened enough or if they are too moist and need to be dried again. Though worth trying, these methods cannot salvage buds that have lost their terpenes due to over-drying.

Ed Rosenthal is a recognized authority on marijuana. In his more than 40 years he has written or edited more than a dozen books about marijuana cultivation and social policy. Signed copies of Marijuana Harvest and other titles can be purchased at EdRosenthal.com.

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