Method for purifying crystals using solvent vapors

A method for purifying THC acid using solvent vapor recrystallization, the steps comprising:

• a) inserting feed material having THC acid into a vessel having walls, an upper portion, and a lower portion with a bottom surface;
• b) exposing the feed material to a hydrocarbon liquid in the vessel in a quantity sufficient to keep liquid present and in equilibrium with gas in the vessel throughout the recrystallization process, forming at least one of a raw extract having THC acid or a suspension containing THC acid crystals;
• c) coating at least one of the walls or the bottom surface of the vessel with at least one of the raw extract having THC acid or the suspension containing THC acid crystals;
• d) heating the vessel and contents thereof;
• e) discontinuing the heating step (d);
• f) forming purified crystals of THC acid or further purifying crystals of THC acid on at least one of the walls or the bottom surface of the vessel;
• g) reclaiming the hydrocarbon solvent from the vessel, leaving therein purified crystals of THC acid and impurities;
• and
• h) opening the vessel and removing the purified crystals of THC acid and impurities therefrom.