A closeup image of a drop of cannabis oil on the end of a needle

Hash oil is an evaporated solution of tetrahydrocannabinol and various other compounds produced by a solvent extraction of cannabis. Despite the similarity in names, it does not resemble hashish. It can be a very potent drug due to its high THC concentration, which generally varies between 70 - 90 percent. Related Honey oil is a specific type of hash oil produced by certain solvents, most commonly butane, and isopropanol. Sometimes called butane hash oil or BHO, or simply "oil", it can range in color from a bright yellowish gold to a dark amber, viscous liquid made by solvent extraction of cannabis resin.[1]


Various terms are used to denote the solvent extract of cannabis. Typical terms are "hash/hashish oil," "honey oil," "____ oil" or "____ honey oil" (where ____ denotes the solvent), and many variations on these terms.

The descriptor "honey" is often used in naming these extracts. The true source/history of the term may be different, but it is most commonly used to designate the color of the extract. "high quality" extracts are commonly translucent and often have a dark gold or dark red color. The extracts are often extremely viscous and can even be made to behave as a solid with material properties similar to a glass (fragile, capable of shattering). Thus the physical appearance and behavior (viscosity) is often compared with that of honey.


Hash oil can be consumed in various ways[2]

  • Smeared on a cigarette or a joint.
  • Adding it to the inner rim of a pipe bowl.
  • Mixed in food (such as space cakes).
  • Vaporized off a scientific bong/bubbler attachment (such as a ti nail and dome, vapor swing, vapor tube, domeless ti nail, e-nail, eclipse vape, and health stone).
  • Vaporized off improvised devices; such as an electric stove element, car cigarette lighter, or pressed between two heated knives (known as blades, spotting or hot knifing). The vapor can then be inhaled through a hollow tube, often an empty pen tube called a hooter.


Hash oil is obtained via extraction of the psychoactive cannabinoids that are present in cannabis. All of the safety guidelines and the basic process and method used to extract cannabis is a generalization of the basic principle of extraction used in a variety of fields. The organic chemistry, natural product, perfume, and essential oil industries all use similar or identical methods to extract and concentrate various other mixtures of chemicals from natural sources or synthetic sources. A solvent capable of dissolving the desired analyte is used to dissolve these chemicals from the physical plant material, which is typically ground or finely divided in order to increase the solvent accessible surface area. The resulting mixture is then filtered to remove the remaining sediment, and evaporated to yield a concentrated extract of resins and essential oils.


As the majority of hash oil is produced clandestinely, without access to the proper laboratory equipment, the main method producers use to control the quality and yield of their hash oil is solvent choice.

The solvent choice for extraction of cannabis is typically made using several criteria: solubility information, cost/availability/suspicion, hazard, and ease of removal. The most common solvent choices are Isopropyl alcohol, butane, ethanol, petroleum ether and naptha. It is no coincidence that these solvents are commonly available in a variety of drug or hardware stores in small unobtrusive quantities and in relatively high purity. The ease of availability and relatively low cost allows producers to minimize suspicion. Other less commonly used solvents include methanol, ethyl ether, propane, supercritical carbon dioxide, R-134a refrigerant gas, acetone and various aromatic compounds such as toluene. Many of these less commonly used solvents are regulated to various degrees in the US and some other countries and access may be restricted. Ethyl ether, especially, is regulated as it is commonly used in the production of various other illicit drugs such as diacetylmorphine and methamphetamine. Traditional solvents are not the only choices. Any chemical with the correct properties may dissolve appreciable amounts of the psychoactive constituents of cannabis. Fatty acids or esters of fatty acids may also dissolve cannabinoids and structurally similar compounds. Vegetable oils (such as canola oil) and animal fats (such as butter) may be used in a modified extraction method to produce non-toxic extracts for use in food. For example, dronabinol, the generic name pharmaceutical name of synthetic THC, is typically prescribed as a solution of the drug in a vegetable oil (sesame oil).

Butane is advantageous to use as it has a boiling point of −0.6°C (31°F), meaning that it will fully evaporate when left for long enough at room temperature. Butane is cheap and widely available in the form of 'lighter refill' cans. Butane also has the advantage of not dissolving the chlorophyll component of whole cannabis - it dissolves mainly the psychoactive resins. Drawbacks include the risk of explosion associated with unsafe use of butane gas, and the possibility of contaminants in the butane or the extraction vessel. BHO, or butane honey oil is a common term for the output produced by butane extraction of cannabis.

Solubility Issues[]

The goal of such a process is the extraction/isolation of the psychoactive constituents. It is rarely possible, however, to selectively extract a single chemical, or group of chemicals, from a plant material like cannabis. Thus any solvent extract will contain a variety of unwanted impurities.

The solvent interaction with analytes is often characterized on the basis of a molecule's polarity. The majority of the psychoactive constituents of cannabis are oligoterpenoides known as cannabinoids. These molecules are composed almost entirely of carbon and hydrogen and only readily dissolve in certain solvents.

The final extract's quality is usually judged, at least partially, on the perceived concentration of impurities. These impurities are usually associated with extracts made using polar solvents like alcohols or acetone. The impurities are most likely the non-psychoactive constituents of the plant material. These impurities may include chlorophyll (which may add green, brown, or red coloring), carbohydrates/cellulose, amino acids, waxes and/or water. Many of the chemicals in these groups are polar and readily dissolve in alcohols or ketones (acetone), but will only partially dissolve in solvents like butane or ethyl ether.

Use of polar solvents may increase the overall yield of an extraction by increasing the relative concentration of unwanted impurities relative to the desired psychoactive constituents.

The most commonly used polar solvents are ethanol and isopropanol.

Solvent Removal[]

The clandestine nature of the production of this material prevents access to useful tools such as a rotary evaporator, which are an indispensable tool in modern natural product and organic laboratories. Producers instead rely on relatively crude and simple methods of solvent removal. Most often, producers simply evaporate the solvent into the atmosphere which is an environmental concern in some cases.

This is the part of the process where many of the accidents/disasters that are associated with hash oil production occur. Nearly every useful solvent is highly flammable. Many of these solvents have vapors that are denser than air, and can "creep" around walls or under doors inside structures. Open flames such as pilot lights or sparks from certain types of electronics can often present hazards even in seemingly safe conditions. Laboratories that deal with flammable solvents use sparkless electronics and fans to remove residual solvent vapors.

The typical methods used by clandestine producers are very simple and use household or easily available tools. In almost all cases, the producer will use a glass or metal container containing the solvent mixture as the vessel in which the evaporation/distillation is carried out. In many cases, the container is simply allowed to evaporate without additional heat. This can take a very long time. In many other cases, heat source are used to facilitate the evaporation. Some producers aid the evaporation process by using fans to increase airflow over the surface of the solvent mixture. The large quantities of solvent vapor that are allowed to escape into a structure or the atmosphere can be extremely dangerous as they are often flammable or explosive and may also be toxic when inhaled in such high concentrations.

When solvents with relatively low boiling points are used, the distillation/solvent removal process can be performed relatively quickly. the low boiling point of these solvents under atmospheric pressure facilitates their quick removal. This is one of the major attractive features of butane as a solvent for extraction.

Naphtha based oil notoriously contains amounts of residual naphtha enough to influence the smell, taste and effects of the product. Many users report feeling sick or having headaches when smoking honey oil extracted by naphtha, hence it is generally accepted that the product poses a greater health risk than with butane-extracted oil. Alcohol-extracted oil also contains plant sugars, which caramelize when smoked to produce a harsh taste.

Removal of residual solvent is extremely important. it can reduce or limit the danger of ingestion of hash oil if done properly. This process has been commonly termed "purging" the material.

Laboratory methods involve vacuum removal of the solvent or lyophilization of the extract. Clandestine methods rarely utilize such methods, and usually involve heating the concentrated solvent mixture until no odor of the solvent is detected. It is common to use a glass container and steam as the heat source for this method. Other producers will attempt to burn/ignite the remaining solvent vapors by controlled combustion using some form of small flame source.

Source Material[]

Generally the whole cannabis plant can be used to produce honey oil or other types of hash oil. Some will use only the buds of the cannabis plant to improve yield since they contain more cannabinoids. This gives an advantage only when using other solvents than butane, because it will improve the ratio of cannabinoids to other plant chemicals. With the butane extraction it will also increase the yield a little bit since there are more cannabinoids to collect, but it will not improve the quality and purity of the oil. Also the parts of the marijuana plant that are not the bud are considered low grade and non profitable so it is turned into the more concentrated oil.


There are an extremely wide variety of dangers associated with hash oil production. Many structure fires and severe burns have been caused when clandestine production accidents occur. The most common danger is from flammability. It is incredibly dangerous to carry out any extraction following these guidelines without proper training, safety precautions, tools, and in a designated location. Regardless of the illegality of cannabis or its extracts, extraction of any material is not recommended outside of a safe controlled laboratory or industrial setting.


Essentially most solvents used to make hash oil are flammable. Some are even explosive when stored under pressure (such as butane or propane). Others may represent storage hazards such as ethyl ether. when stored in the presence of atmospheric oxygen, ethyl ether will polymerize in to a polymeric form of diethyl ether peroxide. it is often seen as a white powder or crust around the cap or at the bottom of a bottle. This material is incredibly explosive and has been the source of countless laboratory explosions throughout modern history. Its explosive power can be compared with that of military explosives, though it is much less stable.


Physical effects[]

The effects of extracted resin are comparable to smoking the same plant from which it was extracted, but often intensified due to its much higher potency. In the case of honey oil, several small drops can produce effects comparable to a much greater amount of plant material. This can sometimes cause overwhelming effects if the extract's high concentration of cannabinoids is not taken into account.

See also[]


  1. King, Leslie A. (2003). The Misuse of Drugs Act. Royal Society of Chemistry. pp. 75–76. ISBN 978-0854046256. 
  2. Kuhn, Swartzwelder, Wilson, Wilson, Foster, Cynthia, Scott, Wilkie, Leigh Heather , Jeremy (2003). Buzzed. W. W. Norton & Company; 2 Rev Upd edition. pp. 139–140. ISBN 978-0393324938. 

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