Why does my potency vary so much between extraction batches?

The short answer: non-quantified compounds can make up significant and varying amount of an extract. Extract content can vary within the same strain, same harvest, and even same day of extraction if all variables are not perfectly controlled. No two buds are the same!

At Confidence, we routinely measure the cannabinoid content, terpene content, and residual solvent content of extracts. For many extracts (especially ethanol soaks and CO2 oil, but also some BHOs) there are significant amounts of impurities in the product that we do not routinely quantify. The list of all the possible impurities would fill up pages, and we only know the identity of some of these impurities (like chlorophylls and associated protein complexes, various types of waxes [not all of which are winterizable], phytosterols, anthocyanins, and even water in some cases).

These impurities come from the cannabis plants being extracted from. For example, in order for extraction to work, the extraction solvent must partly dissolve trichomes in order to get at the cannabinoids inside. Some of the trichome structure is then dissolved in the solvent and ends up as an impurity in the final product; this set of impurities is normally called “plant waxes”, “plant lipids”, phytolipids, etc., and many of them can be avoided or removed by using colder extraction temperatures, shorter extraction soak times, and winterization. Techniques for further impurity removal or avoidance are being regularly investigated by Confidence Analytics employees.
Additionally, there are normally trace-level cannabinoids in every flower and concentrate sample, but sometimes they are present in more than trace quantities.

Since we do not measure these uncommon cannabinoids (like CBL, CBA, and a slew of other things nobody is looking for), it is possible that certain strains with lots of these may always have lower potency.

Lastly, while we believe it is unlikely to be a major contributor, water content in extracts may contribute to lower potency.