// Definition
A measurement of the available water in a substance that indicates microbial growth potential, distinct from simple moisture content. Used in cannabis to determine shelf stability and proper cure level, measured with specialized meters.
// From the Episode
Dr. Mark Scialdone discussed how water activity meters are used in cannabis testing, noting Johnny B has been measuring water activity for years. He explained that potency testing on a dry-weight basis is flawed because labs use different methods to determine moisture content, leading to inconsistent THC numbers across labs. Removing more water artificially inflates THC percentages, creating a perverse incentive for labs to over-dry samples.