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Sep 11, 2025
ASTM International is developing a proposed standard (WK95556) that will aim to identify an accurate technique to determine percent moisture in cannabis flower, harmonization across and between states for moisture determination.
WK95556 is being developed by the laboratory subcommittee (D37.03), part of ASTM’s cannabis committee (D37).
According to ASTM member Morgan Keefer, for cannabis flower products, the label often reflects a moisture conversion (dry weight percentage) which means that all the numbers on the label are heavily impacted by how much water was in the flower.
“The issue with this is there is no standard method for determining how much water is in the flower (which is a basic method) so the methods that are being used for this are all over the place and even the results are all over the place,” says Keefer, senior accreditation officer at A2LA. “Some laboratories may dry in an oven, they may use very hot oven temperatures which evaporate more than just the water weight, they then count the whole difference in weight before and after the oven as 'water weight' and perform the conversion which, if done in this way, would guarantee that all of the cannabinoid and terpene percentages increase across the board.”
The proposed standard is intended to be used by testing laboratories; to be implemented as a required method by state regulatory bodies; and to be added to scopes of accreditation.
ASTM welcomes participation in the development of its standards. Become a member at JOIN ASTM.
ASTM International is a not-for-profit nongovernmental organization that develops voluntary consensus standards and defers to appropriate government authorities to determine the legal and regulatory framework regarding the control and use of cannabis.
November / December 2025
