Solvents
- Butane (boiling point ~−0.5 °C (31.1 °F) ): One of the most common solvents used. Hash oil extracted with butane is often referred to as "butane honey oil", or "BHO" by the marijuana using community.
- Isopropanol (Rubbing alcohol) (usually 99% isopropyl alcohol and 1% water) (boiling point ~82 °C (180 °F)): One of the most common solvents used. Cannabis oil extracted with isopropanol is sometimes referred to as "Iso Oil". The advantages of isopropyl alcohol are that it is commonly available, cheap, and is somewhat less toxic and explosive than is methanol. Unfortunately, because it contains water, many of the water-soluble, non-psychoactive substances are also extracted. The oil yield using rubbing alcohol is twice that of methanol, and is proportionally less potent. Water-soluble components may also give the oil undesirable taste and burning qualities. If the oil is to be re-extracted later with a more selective solvent, however, it matters little what it is like at this point. Once most of the alcohol is evaporated, the water & remaining isopropyl alcohol that was in the solvent remains with the oil.
- Methyl alcohol (also known as methanol or wood alcohol) (boiling point 64.7 °C (148.5 °F) ): This solvent is also commonly employed. Methanol is available at many pharmacies and in larger quantities at industrial chemical supply companies. Methanol is toxic and explosive. Inhalation of fumes makes one sick and even small amounts may cause permanent damage. Any traces of the solvent remaining in the oil product will be hazardous to the consumer. Methanol evaporates at approximately 65 °C (149 °F) and does not extract a lot of the water-soluble component.
- Ethanol (also known as ethyl alcohol or grain alcohol) (boiling point 78 °C (172 °F)): This is a very desirable solvent. It has extraction properties very similar to methanol, but is not as toxic.Denatured alcohol is composed of ethanol with added poison, to deter ingestion and to avoid taxes on beverage alcohol. Depending on what type of poison is used to create the denatured alcohol, the poison may or may not be effectively removed by evaporation. However, denatured alcohol is more widely available and cheaper than poison-free ethanol.
- Petroleum ether (boiling point 30 °C (86 °F) —60 °C (140 °F)): Petroleum ether is a light solvent that is much more selective than any of the alcohols. Extracting with petroleum ether produces an oil that is twice as potent by weight as oil extracted with alcohol. The cannabis material may be extracted directly with petroleum ether but, due to petroleum ether’s highly explosive nature, the oil is usually first removed from the plant material with alcohol and then re-extracted with petroleum ether. This requires a much smaller amount of the dangerous solvent. Petroleum ether is available at hardware stores in many countries, including the US. Petroleum ether should not be confused with diethyl ether, the term "ether" alone more commonly refers to diethyl ether.
- Acetone Boiling point 57 °C (135 °F) Easily available as a solvent and degreaser, Acetone evaporates rapidly and is probably the safest solvent used in health terms. Acetone has been studied extensively and is generally recognized to have low acute and chronic toxicity if ingested and/or inhaled. Acetone has been rated as a GRAS (Generally Recognized as Safe) substance for food use and is produced and disposed of in the human body through normal metabolic processes. The most hazardous property of acetone is its extreme flammability. At temperatures greater than acetone's flash point of −20 °C (−4 °F), air mixtures of between 2.5% and 12.8% acetone, by volume, may explode or cause a flash fire. Vapors can flow along surfaces to distant ignition sources and flash back.
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