Solvent Free Extractions

One amazing property of the cannabis plant is no solvents are necessary to effectively concentrate the active components.  For many plants, their active metabolites are found within plant cells, and solvents are necessary to dissolve them and remove them from the inert plant matrix.  In contrast, cannabinoids collect predominantly in the heads of glandular trichomes, which can be removed using agitation and sieving, or heat and pressure.  Trichome heads can be separated from plant matter by sieving dry cannabis, or by agitating cannabis in ice water.  These processes concentrate the cannabinoids significantly but are not really “extractions”.  They are more akin to a post harvest agricultural process like harvesting seeds from a cut plant, or removing husks from rice.  When separated trichomes are loose they have the appearance of fine sand, known as kief.

The trichome head has a waxy cuticle which is like a skin to hold all the contents inside.  When exposed to small amounts of heat or pressure these heads can burst causing the cannabinoids and terpenes to leak out to form a very sticky resin.  Traditionally, kief would be pressed with some heat and pressure to make hashish.  The trichome heads break and the sticky resin causes them all to stick together to make a malleable solid resin.  This process of making kief and hash concentrates the cannabinoids significantly, and also significantly reduces the volume of the end product, making storage and transport easier.  Hashish has been produced by cultures around the world for thousands of years.

More recently, a new technique has arisen to make a more concentrated resin using just heat and pressure.  Using high pressure (1-10 tons) and heat (50-100C) herbal cannabis, kief or hash can be pressed through a porous surface (like a nylon mesh) to produce a high potency extract called rosin.  This process bursts the trichomes, but unlike hash with hash, the liquid resin is separated from the solid portions of the trichome cuticle and leaf to leave a true concentrate.  By leaving behind the solid portions, rosin can be vaporized, dabbed, or used to make various formulations.  Rosin is the simplest and easiest method to make a cannabis concentrate, with the processing