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The tetrahydrocannabinol (THC) content of hash oil varies tremendously, since the manufacturers use a random assortment of marijuana plants and preparation techniques. Dealers sometimes cut hash oils with other oils.
Hash oils seized in the 1970s had a THC contents ranging from 10 to 30%. The oil available on the U.S. West Coast in 1974 averaged about 15% THC. Samples seized across the United States by the Drug Enforcement Administration over an 18-year period (1980-1997) showed that THC content in hashish and hashish oil averaging 12.9% and 17.4%, respectively, did not show an increase over time. The highest THC concentrations measured were 52.9% in hashish and 47.0% in hash oil.
- Cannabinoids: THC (~ 30%) and THCA (~ 60%).
- Monoterpenes (~ 5%): β-pinene, myrcene, β-phellandrene, cis-ocimene, terpinolene, and terpineol.
- Sesquiterpenes (~ 5%): β-caryophyllene, humulene, δ-guaiene, γ-cadinene, eudesma-3,7(11)-diene, and elemene.
Hash oil is consumed usually by smoking, ingestion, or vaporization. Vaporizing hash oil is also called taking a "dab" or known colloquially as "dabbing", some times referred to as "dap" from the English verb to daub (Dutch dabben, French dauber), "to smear with something adhesive". Dabbing devices include special kinds of water pipes ("oil rigs"), and vaporizers similar in design to electronic cigarettes.
Hash oil is produced by solvent extraction (maceration, infusion or percolation) of marijuana and/or hashish. After filtering and evaporating the solvent, a sticky resinous dark liquid with a strong herbal odor (remarkably different from the peculiar odor of hemp) remains.
Fresh, undried plant material is less suited for hash oil production, because much THC and CBD will be present in their carboxylic acid forms (THCA and CBDA), which may not be highly soluble in some solvents. The acids are decarboxylated during drying and heating (smoking). Fresh, undried plant material is best suited for concrete production.
A wide variety of solvents can be used for extraction, such as chloroform, dichloromethane, petroleum ether, naphtha, benzene, butane, methanol, ethanol, isopropanol, and olive oil. Currently, resinoids are often obtained by extraction with supercritical carbon dioxide. The alcohols extract undesirable water-soluble substances such as chlorophylls and sugars (which can be removed later by washing with water). Non-polar solvents such as benzene, chloroform and petroleum ether will not extract the water-soluble constituents of marijuana or hashish, and will yield a somewhat more potent oil as a result.
The oil may be further refined by 1) deacidification, or removing the heavy aromatic carboxylic acids with antibiotic properties, which may cause heartburn, gallbladder irritation, and resistance to hemp antibiotics; 2) conversion of CBD to THC. Process 1) consists of dissolving the oil in a nonpolar solvent such as petroleum ether, repeatedly washing (saponifying) with a base such as sodium carbonate solution until the yellow residue disappears from the watery phase, decanting, and washing with water to remove the base and the saponified components (and evaporating the solvents). This process reduces the oil yield, but the resulting oil is less acidic, easier digestible and more potent. Process 2) consists of dissolving the oil in a suitable solvent such as absolute ethanol containing 0.05 % hydrochloric acid, and boiling the mixture for 2 hours. The latter method may be used to convert CBD oil to THC-CBD oil, the true reason why CBD oil is so popular.
One pound of marijuana yields from 1/5 to 1/10 of a pound of hash oil. The oil may retain considerable residual solvent: oil extracted with longer-chain volatile hydrocarbons (such as naphtha) is less viscous (thinner) than oil extracted with short-chain hydrocarbons (such as butane).
Colored impurities from the oil can be removed by adding activated charcoal to about one third to one half the weight or volume of the solvent containing the dissolved oil, mixing well, filtering, and evaporating the solvent. When decolorizing fatty oils, oil retention can be up to 50 wt % on bleaching earths and nearly 100 wt % on activated charcoal.
Most of the solvents employed are flammable, making the extraction process dangerous. Several explosion and fire incidents related to hash oil manufacturing attempts in homes have been reported.
Hash oil should be stored in airtight containers and protected from light. When exposed to air, warmth and light (especially without antioxidants), the oil loses its taste and psychoactivity due to aging. Cannabinoid carboxylic acids (THCA, CBDA, and maybe others) have an antibiotic effect on gram-positive bacteria such as (penicilline-resistant) Staphylococcus aureus, but gram-negative bacteria such as Escherichia coli are unaffected. The effect of hash oil on fungi and virii is unknown.
- Tincture of cannabis
- Oleoresin capsicum
- Tall oil
- Cannabis flower essential oil
- Hemp oil
- Juniper tar
- Liquid smoke
- Ed Rosenthal, Beyond Buds: Marijuana Extracts, 2014.
- Michael Starks (1993), Marijuana Chemistry: Genetics, Processing, Potency (2nd ed.), Ronin, pp. 111–126, ISBN 9780914171393
- "Cannabis: Overview", World Drug Report (PDF), United Nations Publications, 2014
- Marilyn A. Huestis; Michael L. Smith (2007), "Human Cannabinoid Pharmacokinetics and Interpretation of Cannabinoid Concentrations in Biological Fluids and Tissues", in Mahmoud A. ElSohly, Marijuana and the Cannabinoids, Humana Press, pp. 205–235
- Rudolf Brenneisen (2007), "Chemistry and Analysis of Phytocannabinoids and Other Cannabis Constituents", in Mahmoud A. ElSohly, Marijuana and the Cannabinoids, Humana Press, pp. 17–49
- Luigi L. Romano; Arno Hazekamp (2013), "Cannabis Oil: chemical evaluation of an upcoming cannabis-based medicine" (PDF), Cannabinoids 1 (1): 1–11
- Samuel Johnson (1785), "daub", A Dictionary of the English Language 1 (6th ed.), p. 541
- Alison Hallett (2013-02-20), "Hash Oil is Blowing Up Across the U.S. - Literally", Wired
- Yechiel Gaoni; Raphael Mechoulam (1964), "Isolation, Structure, and Partial Synthesis of an Active Constituent of Hashish", Journal of the American Chemical Society 86 (8), doi:10.1021/ja01062a046
- Alfred Thomas (2007), "Fats and Fatty Oils", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley, p. 31
- Jan Kabelik (1955), "Hemp as a medicament" (PDF), Acta Univ. Olomuc. 6