Sunday November 18, 2018

By Matthew Mongelia


With sweeping acceptance of cannabis moving across the world, the marijuana plant is finally stepping into the limelight. Store shelves that once offered an array of options for hiding bud now sell cannabis display cases. Companies like Smokus Focus have sprung up with devices to maximize the flower-viewing experience, flooding the specimen in question with bright LED light. With all the increased exposure, it begs the question, what exactly does light do to cannabis?

The Radiation Situation

Since the days of Edison and Tesla, light has become a part of everyday modern life. In fact, it’s so common that we tend to forget what light is. Light is radiation, specifically electromagnetic radiation within a certain spectrum. Radiation degrades organic material when sufficient energy is transferred. This is evident to anyone who’s gotten sunburn, but is also the same process that turns grass brown and fades untreated wood.

Flash Photography
Flash photography is prohibited in many museums to prevent light degradation. photo credit

In museums, flash photography is prohibited due to the damage radiation might do to artifacts. If you have ever visited the Star Spangled Banner in DC, you’ll know that it’s kept in a special darkened room, with no photography allowed. This is because the flag is made of cotton, and cotton is organic, thus more susceptible to light degradation. So will light harm your weed? In short, yes, light will begin to degrade cannabis as soon as it is cut from the plant.

Not All Light is Equal

Perhaps all this radiation talk has you looking for the nearest fallout bunker for rent on Air BnB, but fear not, most light is harmless. When sufficiently energized, radiation can knock electrons off atoms, resulting in ions. This “ionizing-radiation” can damage living cells (and the DNA within), which is how radiation exposure increases the risk for cancer.

Most visible light is non-ionizing radiation, and thus, generally harmless to humans and living things (including cannabis).

The complicated part lies in ultraviolet (UV) radiation. Ultraviolet light sits right along the line between ionizing and non-ionizing radiation on the electromagnetic spectrum. The difference is so close that UV light is further subdivided, with the lower half of UV referred to as “soft” UV, and the upper half considered ionizing radiation. Due to the unique properties of UV light, some of the non-ionizing spectrum is even able to exhibit ionizing-like effects. Multiple studies have shown ultraviolet light to be a primary contributing factor to THC breakdown.

CFL lights emit UV light so try to keep your bud out of direct contact. photo credit

Many light sources, including the popular Compact Fluorescent Lamp (CFL) bulb (the type one might find in most commercial businesses, including a dispensary), emit a small portion of UV light (sunlight that reaches earth also carries a small portion of UV, typically more than commercial bulbs). As THC is a relatively unstable compound, only a small amount of light is required for degradation. For this reason, cannabis light exposure should be minimalized wherever possible. If your local dispensary keeps their stock in large clear jars, it might be wise to look elsewhere.

What Evidence Do We Have?

A few studies have delved into the degradation of THC. THC itself is not a very stable compound and will degrade into CBN with exposure to light, air and heat.  A 1976 study determined light to be the largest factor of the three. A more recent four-year study delved deeper into the phenomenon, finding “on the average, the concentration of THC in the plant material decreased by 16.6% ±7.4 of its original value after one year, 26.8% ±7.3 after two years, 34.5% ±7.6 after three years and 41.4% ±6.5 after four years,” for cannabis stored at room temperature.

Researchers found that “the higher the concentration of THC, the faster the degradation over the first one or two years.”

Additionally, “the degradation of THC appears to proceed at a higher rate for the first year than subsequent years and levels off after two years to a rate of loss of approximately 7 per cent per year.” At a loss rate of roughly 1.3% per month (and a wide degree of variance), the majority of cannabis smoked within a year of harvesting should be relatively close to ideal freshness.

Other Factors

Oxidizers (Oxygen being the most common) are substances that cause other compounds to lose electrons (become oxidized). Much like light exposure, oxidation contributes of the process that converts THC to CBN. This is why some luxury cannabis companies have taken to packaging in nitrogen, which has a lower oxidation rate than O2.

Handful of Weed
Light, air and heat exposure all contribute to cannabinoid degradation.

Research has also found that heat plays a primary roll in cannabinoid breakdown. Studies in the 70’s determined that lower temperatures showed a slower rate of cannabinoid loss, with temperatures below freezing to have the lowest rate of cannabinoid loss. Anything between frozen and ambient room temp (70~ F), was shown to be fairly stable, but temperatures above will start to quickly degrade THC.

How to Properly Store Your Cannabis Stash

When it comes to storing your cannabis, controlling for light, air, and heat will keep your buds fresh the longest. For light, keep flower in an opaque container. A drawer works pretty well also. Mason jars are the industry staple for a cheap and readily available airtight container. Heat should not be a problem so long as you are keeping your bud at room temperature, but maybe don’t store it near the radiator or heating vent. Freezing is technically optimal, and works well for long-term storage. Trichomes may become brittle and fall off, but if kept away from light and air, should avoid cannabinoid degradation. Ultimately, there are many ways to properly preserve your stash so try a few options out and pick what’s best for you!

What are your thoughts on light degradation in cannabis? Comment below!


Matthew Mongelia Matthew Mongelia

Matthew Mongelia is the Content Manager for He holds an MFA in Writing from The School of the Art Institute of Chicago, and a BFA in Creative Writing from CUNY Brooklyn College. He has worked in the industry in numerous roles for over 5 years while covering cannabis content from coast to coast. Like so many in the industry, he first became acquainted with cannabis as a medical patient, and has been a passionate advocate for the plant ever since. He is a writer for the comic Dark Beach, and has previously covered music and cultural content for SOL REPUBLIC.

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