Not all THC % are created equal

 In Cannabis Education

It can depend on how moisture content is accounted for in the final potency calculation


The Market Today

THC is the dominant player in the Cannabis market at large. Most customers opt for products offering them the most THC for the least amount of money.

The market reflects this demand in it’s race to the top in terms of potency. Extracts are becoming more and more concentrated, some upwards of 90% THC(a) and the best selling strains of flower are consistently being reported at potencies of 20% THC and higher.

With so many critical decisions being made on the basis of THC alone, it is important to know how these potency percentages are generated and what they mean for you.

Labs can report their flower potency results in two ways: as mg/g dry mass or mg/g  at the actual moisture content at the time of sale.

Dry Mass

Removing the water moisture from a flower sample is a necessary part of the lab testing procedure. When this moisture is removed, the total mass of the flower decreases and the mass of the cannabinoid content remains the same.

THC now makes up a greater % of the flower’s mass.

Typically this gives a 2-4% higher potency reading.

But this is not what you are buying.

Actual Moisture Content at the Time of Sale

Many large-scale growers cure their product after harvest until it reaches a relative humidity of 50-54%. This range is selected to give the flower the qualities consumers want: an even burn, and optimal flavor and effect. 

Typically this gives a 2-4% lower potency reading than the dry mass calculation because the moisture is accounted for in the flower.

Which Are You Buying?

At CVD/SVW we report our THC %s  based on the average moisture content at the time of sale because this is a fair reflection of the product you are buying.

The Detail

There are many factors that go into accurate reporting of cannabinoid content and there are no industry standards on which methods should be used so that adequate comparisons can be made from lab to lab.  This is made evident  in the numerous studies that have shown that comparable Cannabis samples can be sent to different labs and that each lab will generate a different result.  One of the significant reasons for these differences when reporting potency of flower is how moisture content is accounted for in the final potency calculation. In general, there are two ways that labs report their flower potency results: as mg/g dry mass or mg/g of flower at the actual moisture content at the time of sale.

When we talk about potency in Cannabis flower, it is important to note that what is being measured is the proportion a cannabinoid’s mass (in this example, THC) occupies relative to the total mass of the flower sample. For example:

1 gram of Cannabis flower with a 16.5% THC potency means that 16.5% of the flower’s mass is THC.

16.5% of  1 gram =  .165 of a gram of THC or 165mg

This is a calculation for final THC potency, since THCa is the dominant cannabinoid in raw and cured plant material.  THCa is converted to THC with heat and the loss of an acidic carboxyl group (and mass), so a conversion constant is used to calculate the final THC mass (potency).

Moisture plays a very important function in this calculation because a considerable portion of a 1 gram flower is water.  If this water is removed, the total mass of the flower decreases, but the mass of cannabinoid content remains the same. The cannabinoids are bound up in the oil of the resinous trichomes.  With less water mass, THC content becomes a larger percentage of the total mass of the flower. Completely drying out the sample (desiccation) is a necessary part of the sampling procedure in lab testing.  If calculations are based on the dry mass data collected with a moisture balance, results can then be reported as a percentage of this dry mass or adjusted to reflect the actual moisture content at the time of sale.

Many large-scale growers cure their product after harvest until it reaches a relative humidity between 50-54%. This range of relative humidity has been selected because flower maintained within it has the qualities that consumers want: an even burn and optimal flavor and effect. 

At CVD/SVW we report the THC content of our flowers based on the average moisture content at the time of sale. We believe that this is an accurate representation of what a patient is purchasing.  As part of our internal process and data tracking, we also calculate using the dry mass method. The table below shows dry mass potencies for six of our most popular strains:  

Conclusion

It is critical that you ask your dispensary which method they use to report cannabinoid potency percentages. As seen from the table above, the difference between Actual Mass and Dry Mass reporting can equate to as much as 23.6mg/g (660mg/oz) of flower. If THC is the prime deciding factor in selecting your products you will want to have this information so that you can make the best decisions for both your health and your wallet.
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