Ever wonder how much it matters if you leave your weed sitting in the sun for a while?…

We continue to enjoy the “Chef’s Kiss” flower from @Ocean Breeze Cultivators. The convenience of rolling quick joints from the shake gives unexpected pleasure.

Most readers know that the main cannabinoid in marijuana flower is usually THCA, the acid precursor to THC. The level of THC that’s found in cured flower is usually around 0.7 – 1.5%. As cannabis sits around for longer, THCA gradually turns into THC at a rate that can be noticed if the temperature is above 40 °F (4 °C).

We tested degradation of cannabis compounds in weed and in solutions. We encountered hiccups, but learned a little about preserving cannabis.

Previous experiments confirmed that cannabis flower stored in a cabinet of my home changes too little to notice in one week. Last week’s flower, stored in clear plastic tubes in the sun, degraded noticeably within a week. We weighed the cannabis as usual, but instead of immediately extracting, we taped the samples to the window. We drew portions of the solutions from last week up into syringes and taped them to the window as well, storing controls in the dark.

Last week, we reported our batch of shake at 15.5% THCA, 1.9% THC. After a week in the sun, it measured 14.8% THCA, 1.2% THC; each had dropped slightly. Our nugs were 17.7% THCA and 1.4% THC before, 17.9% THCA and 1.1% THC after sun.

It looks like leaving your weed out in the sun can degrade it, but leaving it in a sunny car for an hour or two won’t hurt it too bad.

The solutions illustrate extreme degradation. Molecules in liquid react faster than those in solids; that’s why chemists have tubes and flasks. Orange Photonics, Inc. says we should measure solutions ASAP.

The solutions turned orange in sunlight. The background absorbance was so intense that the “Shake” extract left in the sun couldn’t be measured by hashtag#LightLab at all, and it perturbed the measurement of the “Nugs” sunlit solution. In dark, the shake solution went to 12.6% THCA and 3.7% THC, suggesting nearly perfect conversion of THCA to THC.

The sunlit nugs solution tested at 12.3% THCA and 2.8% THC, while the dark solution tested at 15.0% THCA and 3.4% THC. Again, it seems that, in the dark, THCA converted smoothly to THC, but that sunlight/heat degraded cannabinoids.

To summarize, cannabinoid compounds were robust in cannabis flower but degraded in solution. In dark solutions, THCA converted cleanly to THC without losses. In sunlit solutions, THC was significantly degraded simultaneous to decarboxylation of THCA. In flower matrix, degradation was much slower.

Limitations: few samples, no measure of exposure, no true control for the dry flower samples in the window. The window glass and plastic tubes block UV, the most energetic light; the sun provides mostly visible light and warmth.