A group of researchers in Vancouver are trying to help cannabis pre-roll manufacturers better understand the most effective and efficient particle size for ground cannabis flower in a joint.
“Our aim is to provide cannabis pre-roll manufacturers with tools to better control the delivery of cannabinoids upon smoking of a pre-roll, thus allowing the user to be better informed on the amounts being consumed during joint smoking” notes a paper shared online earlier this year. Researchers also shared their findings at the e Canadian Chemistry Conference and Exhibition in Vancouver in June.
With the growing popularity of pre-rolls, which continue to increase in popularity in Canada, the research team wanted to look at how the particle size of ground cannabis flower impacts the effectiveness of cannabinoid delivery to the consumer.
The study looked at samples of ground cannabis separated into 1, 3, and 5-mm particle sizes. They rolled half-gram joints and “smoked” 18 of them using a Cambustion Smoke Cycle Simulator. The machine takes a 50 cc “puff” of cannabis at a time until the pre-rolls are finished.
Researchers took a sample via a filter from three puffs of the joint, taken at the beginning, middle, and end of the joint, and then analyzed those filters to see the total amount of cannabinoids present.
They found that the lowest amount of cannabinoids was delivered at the beginning of the joint, with the highest at either the end or the middle.
Both the 1-mm and 3-mm joints showed around a 50% increase in THC delivery from the first sampled puff to the middle of the pre-roll, while the 5-mm samples showed a 500 percent increase.
The results also showed that the amount of CBD delivered in each measured puff was higher than that of THC in absolute terms, ranging from 2.3 mg/puff to 6.1 mg/puff. The 1-mm and 3-mm particle sizes showed an increase in the amount of CBD delivered from middle to end, while the 5-mm CBD particles showed larger increases at the end of the joint.
Overall, the results showed that a smaller particle size burned more easily, which they say should create more “high potency” puffs.
The 1-mm and 3-mm ground cannabis particle sizes delivered 16–19 mg of THC, in comparison to the 5-mm joint which delivered 28 mg of THC. When measuring CBD, they found that the 5-mm particles delivered around 100 mg CBD per half-gram joint, compared to the 1-mm and 3-mm joints which reached around 90 mg CBD per pre-roll.
So while only about half (34–59 percent) of the THC in each joint was transferred to the theoretical consumer, the amount of CBD transferred in each puff was closer to 100%.
However, while the smaller particle size seemed to be more efficient at delivering THC to the consumer, it also meant the joint would burn faster, potentially countering this effect. Whereas a larger particle size was less efficient in delivering available THC but because it burned slower, it might provide more THC overall throughout the course of consuming the pre-roll.
This same trend was not noticed with CBD.
“Analogous to a kindling fire that burns vigorously, it would make sense that a 1-mm particle size leads to a greater propensity for uncontrolled combustion,” notes the research paper.
“In the case of the larger 5-mm particle size, the low reproducibility could simply be attributed to the additional puffs these joints needed to ignite at first. Moreover, as these joints took significantly longer to complete and thus have larger puff counts, it is unsurprising that the puff count reproducibility might be slightly higher. However, the kindling analogy does not appear to apply to the 1-mm CBD joint which smoked very reproducibly, suggesting that other factors might be encouraging controlled burning, such as flower humidity.”
“There’s a lack of quantitative research on joint smoking. I want to understand what happens during inhalation on the chemistry side,” researcher Markus Roggen, president and chief science officer of Delic Labs, a cannabis and psilocybin research facility in Vancouver, British Columbia told Scientific American.