"Cannabidiol (CBD) oil is essentially a concentrated solvent extract made from cannabis flowers or leaves that is dissolved in an edible oil such as sunflower, hemp, or olive oil. Solvents used can vary from relatively innocuous organic solvents (ethanol, isopropyl alcohol) to more harmful ones (petroleum-ether, naphtha), or even supercritical fluids (butane, CO2). The exact conditions and solvents applied have a great impact on, for example, the taste, color, and viscosity of the final product. Because many other plant components are co-extracted with the desired cannabinoids present in the herbal material, these are sometimes removed by a treatment known as “winterization.” By placing the extract in a freezer (–20 to –80°C) for 24–48 h, components with a higher melting point such as waxes and triglycerides, as well as chlorophyll will precipitate, so they can be removed by filtration or centrifugation . This treatment can significantly improve the taste and color of the final product.
"Cannabis oils may contain various concentrations of CBD, tetrahydrocannabinol (THC), and minor cannabinoids, mainly depending on the cannabis variety used for extraction. The most popular product currently is CBD oil, but for example cannabigerol (CBG)-rich oil has been spotted as well , and others will very likely follow soon. The THC-rich type of cannabis oil has already been known for some years, and is generally known under the name “Simpson oil” . Terpenes may or may not be present in these products, depending on the preparation method used . Because they are highly volatile, elevated temperatures (such as those applied during drying of plant materials, or during the evaporation of solvents) may result in a significant loss of terpene components . However, it is possible to capture evaporated terpenes by condensation, and reintroduce them back into the final oil. Additional ingredients may be added to further adjust properties such as color, viscosity, taste, or shelf-life stability."
Hazekamp A: The Trouble with CBD Oil. Med Cannabis Cannabinoids 2018;1:65-72. doi: 10.1159/000489287