[2] Preparations of hash oil may be solid or semi-liquid colloids depending on both production method and temperature and are usually identified by their appearance or characteristics.

It is generally thought to be indistinct from traditional hashish, at-least according to the 1961 UN Single Convention on Narcotic Drugs that defines these products as "the separated resin, whether crude or purified, obtained from the cannabis plant".

Gold described the use of alcohol and activated charcoal in honey oil production by 1989,[17] and Michael Starks further detailed procedures and various solvents by 1990.

[6] Smoking or vaporizing hash oil is known colloquially as "dabbing",[6] from the English verb to daub (Dutch dabben, French dauber), "to smear with something adhesive".

[4][21] 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.

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.

Non-polar solvents such as benzene, chloroform and petroleum ether will not extract the water-soluble constituents of marijuana or hashish while still producing hash oil.

Process 1) consists of dissolving the oil in a non-polar 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).

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.

[23] These systems typically entail: a vessel that holds the solvent, material columns to hold the plant material, a flow meter to measure the volume of solvent entering the plant material, a recovery vessel(where heat is applied via an external jacket) to convert the liquid solvent into a vapor and separate it from the THC, CBD, or other cannabinoids/byproducts, and some form of a heat exchanger to then convert the hydrocarbon vapors back into a liquid form prior to returning to the original vessel.

[24] The many different textures/types of hydrocarbon extracts include:[25] Hash rosin has recently become a top quality, highly prized product in the cannabis market.

[26] For dabbing, it is considered to be the cleanest form of concentrating cannabis,[27] as it requires only ice, water (instead of organic solvents like butane), heat, pressure, and collection tools.

[29] These are sometimes isolated and sold as one of the highest quality, most expensive cannabis products in the market today, known as "full melt"[30] because it will dab fine without having to be pressed.

"Full spectrum" hash rosin will normally come from 45μ-159μ, as smaller and larger particles are likely to be too unrefined or broken stalks of the trichomes.

In Canada, hash oil – defined as a chemically concentrated extract having up to 90% THC potency – was approved for commerce in October 2018.

[34] On 8 November 2019, the Centers for Disease Control and Prevention (CDC) identified vitamin E acetate as a very strong culprit of concern in the vaping-related illnesses, but has not ruled out other chemicals or toxicants as possible causes.

[6] In 2019 following an outbreak of illnesses additives added to vape pen mixtures were found to be causing breathing problems, lung damage, and deaths.

While health issues of the lungs may be exacerbated by use of hash oil, it is not known to cause side effects not already found in other preparations of cannabis.