What’s the difference between solvent, non-solvent, solventless, and solvent-free? These terms are increasingly common to see on the menu in dispensaries, but they can cause some confusion, so let’s examine the real meaning behind them within the context of the cannabis world. Solvent extracts are those that are carried out using a (usually a hydrocarbon like purified butane gas) solvent to dissolve the active ingredients and separate them from the plant material. Solventless or non-solvent is a label applied to products that have been extracted mechanically, without the use of solvents. Now, here’s where it can get a bit confusing? Solvent-free is a term used to describe products that were originally extracted with a solvent but later distilled in a laboratory to remove any trace of solvent residue. So they started as solvent extracts but now are 100% free of any residual solvents, as opposed to a well-purged BHO which will always contain a certain, however minuscule, amount of solvent.
Non-solvent extraction processes usually involve using ice to chill cannabis flowers to sub-zero temperatures, agitating the resin glands to detach from the epidermis of the flowers. Heat and pressure extraction methods are sometimes implemented to make non-solvent concentrates as well. Typically speaking, they're smooth-hitting concentrates that highlight the product's aroma, flavor and overall effects better as compared to other extraction methods.
Recently, non-solvent concentrates like rosin and full-melt bubble hash have risen to popularity since they are extracted without the use of chemical solvents, comparing similarly to the cannabinoid and terpene profiles of solvent-based extracts. Non-solvent concentrates are arguably considered a healthier form of concentrate due to the absence of any residual solvent on a parts per million (PPM) scale, although all medical and legal solvent-based concentrates produced are purged and tested extensively to ensure residual solvent ppm levels are in adherence with FDA regulations.
Rosin is extracted directly from the flowers – traditionally made from the heating and pressing of hand extracted compounds. As the industry has grown there are now industrial size presses that can obtain rosin on a large scale. This concentrate is totally solvent-free so can give patients peace of mind if they are concerned about what is in their medicine. Rosin also retains terpenes so is just as flavorful as other kinds of cannabis concentrates.
Kief is the simplest and most traditional type of concentrate available. The process used to extract it typically involves cannabis flower and specialized, fine filtering screens or tumblers. By rubbing the flower against the screen, trichomes are agitated and isolated, effectively producing product comprising of collected trichomes. Anyone can extract their own kief through a three-chamber grinder, which features a screen in the bottom level to help collect the trichomes. Depending on how coated with trichomes the flowers being used are, it may take a few weeks to get a decent amount to consume.
Kief is very fine in texture and often takes on a light brown or tan coloring and mimics the flavor of the flower it came from. It can be used on top of a bowl or consumed on its own. As mentioned earlier, this form of cannabis is more potent because the majority of cannabinoids and terpenes are found in trichomes.
Bubble hash (also known as water hash or ice water hash) is a non-solvent product made using ice, water, and fine micron bags (often referred to as "bubble bags") to filter out plant material and other waste. Bubble hash is a popular concentrate (especially for those new to the concentrate space) that originally gained momentum around 10-12 years ago. Producing bubble hash is debatably the safest extraction technique known to man.
Ice water is used throughout the process to freeze the trichome glands, making it easier for them to become agitated, snap off and sink to the bottom (as trichomes are heavier than water), while unnecessary plant matter separates and rises to the surface. The resulting product is extremely rich with trichome heads and stalks, although additional sieving and drying is necessary to remove any residual plant matter and evaporate any additional water.