It seems simple; Oxford defines extraction as “the act or process of removing or obtaining something from something else.” And rosin is a cannabis concentrate made using heat and pressure. But rosin falls into the extract category while hash is a separation for reasons not found in the lay dictionary.
A chemistry textbook instead defines extraction as a change of phase. And THC-acid, the form of THC made by the plant, changes phase when it dissolves into a liquid solvent. The water dissolves some chlorophyll, for example. But trichomes, nor the plant material, coalesce into the water when making hash.
The technical definition of extraction, which is “synonymous with the general phenomenon” in the process of distribution, is “the apportionment of a solute between two phases.”
Hash is a separation
Abrasion knocks glandular heads that contain the rich body of terps off of cannabis flower. Hash is a collection of these heads, which are known as trichomes. And water is a solvent used in the hash-making process. Yet, hash-making does not require solvents. Water instead assists in separation rather than as a solvent. Hash is, therefore, mechanical separation and not an extract in the strict chemical nomenclature.
A solute is “the minor component of a solution which is regarded as having been dissolved by the solvent.”
Change phases with rosin
If we define rosin as an extract (distribution), we have to prove a change of phase occurred. THC-a must also dissolve during the process of extraction. Otherwise, rosin is a mechanical separation in the same category as bubble hash or kief.
Dissolution involves “the mixing of two phases with the formation of one new homogeneous phase (i.e. the solution).” A phase is the “entity of a material system which is uniform in chemical composition and physical state.”
Heat can melt substances in cannabis and its extract. Presses likely dissolve some solids given the temperatures used to make rosin. Furthermore, melting THCa with heat alone will likely cause more decarboxylation. This implies that something else causes a change in phase during the press.
Cannabis contains solvents in the form of terpenes. If hot botanical solvents do not dissolve THC-a — how does the cannabinoid squeeze through a micron-sized filter? This suggests that rosin presses smash THC-acid out of its trichome’s waxy protection. If rosin is a mechanical separation, then it must be pulverized THCa. But if hot terpenes liquidy solid cannabinoids, then rosin appropriately sits in the extract category.
Let us know in the comments how you define rosin. And do you think hash is a separation or extraction?