Cannabis extracts are a concentration of the cannabinoids, terpenes and plant oils without the plant material. A solvent is used to strip the trichomes and their contents from the plant in order to have a more pure, less carcinogenic medicine to smoke or ingest.
Various techniques and solvents are used to extract cannabinoids and terps, each with their own safety profile and risk factor. The person doing the extract must be a knowledgeable expert as it can be quite dangerous for the maker and the patient.
Each solvent has its own advantages, disadvantages and safety guidelines that need to be considered.
Hashish/Charras: This is the oldest method of making extracts. It is made using either fresh live plants (Charras) or cured Cannabis flowers (buds) for Hashish. A person rubs the buds by using the palms of their hands. As the sticky resin sticks to the hands it is scraped off and pressed into a putty.
Butane: This method is used to make high-end extracts that are clear and free of chlorophyll and other plant material. This method does capture the terpenes, but the amount harvested will depend on the plant material used, as well as the skill and technique of the extract artist. Using dry cured bud or fresh frozen techniques will also play a major roll in how active (decarboxylated) the extract is. In theory, Butane can be easily removed (purged) from the extract ensuring its clean and safe for human consumption. The reality is that in order to make a medicinal grade extract you need to have a vacuum oven to extract the butane efficiently and professionally.
Once the flowers are washed with butane, the Extract Artist will be able to manipulate the substance into many different forms such as dab, wax, shatter, crumble etc.
Ethanol: Ethanol is a great way of extracting medicine. This method is sometimes called the Rick Simpson method (RSO). Rick Simpson helped tremendously with the medical Cannabis movement worldwide since he cured his own cancer using this method.
Ethanol will break the plant membranes releasing chlorophyll along with terpenes and cannabinoids. After reducing the alcohol and cannabis mixture down by evaporating the ethanol you are left with only the sticky cannabinoids and plant fats. The temperature and seep time will also have an effect on how dark or light the extract is.
Isopropyl Alcohol: This type of alcohol has a higher molecular weight than Ethanol which will make it more difficult to purge. There are two techniques that are widely used in South Africa to extract cannabinoids. One being a FECO extraction type oil, where you soak the flowers for a few days and then evaporate the Iso.
The second is called QWISO (Quick Wash), where the flowers are briefly washed with the alcohol. This will strip a lot of the cannabinoids but won’t break all the plant cell membranes, therefore not releasing as much chlorophyll. The oil is lighter than normal FECO.
At the end of the day no one needs to be making medicine with ISO.
Hexane: This is a very good solvent, but without a professional lab you cannot successfully purge the hexane from the oil, making it dangerous for human consumption.
CO2 Supercritical Fluid Extraction: This is the cleanest and safest way of extraction. It is also the most technical. The CO2 acts as a solvent when it is between liquid form and gas form. This is called the supercritical stage. Seeing that the solvent used is CO2 would make it easier to “clean” or purge the medicinal oil. The reality is that if the CO2 used still has some heavy metals contained in it, it will likely be left in the oil after purge. Any extract is only as clean as the solvent used.
Rosin: This is a true solvent-less technique. The cannabis flowers are pressed using steel plates that are heated and pressed to between 1-20 tons of pressure depending on the extract artist. The flavour from this extract can be very good if high quality flowers are used.
There are many more methods and solvents used to make extracts. In theory most of them are quite safe IF extracted using lab like techniques. Due to the black market growing over the years, the techniques have been perfected by some.
Even the very hazardous substances such as acetone and benzene have been used to extract. These solvents in theory could work…if you have a lab. If you don’t have a lab then don’t use dodgy solvents.