Hashish (often shortened to hash, and also referred to by countless slang terms such as **** or chocolate) is a psychoactive drug derived from the Cannabis sativa plant. It is solid, of varying hardness and pliability, softening under heat. Its colour can vary from reddish brown to black, and can also be greenish or golden. It is usually smoked in pipes, and sometimes in joints mixed with tobacco or Cannabis buds. It can also be added to cookies or other food and ingested. Hash is used for its relaxing and mind-altering effects. Many people have claimed that using it gives them great insights.
Hashish is comprised of the compressed trichomes collected from the leaves and flowers of a mature, flowering Cannabis plant. Certain strains of Cannabis are cultivated specifically for their ability to produce large quantities of trichomes, and are thus called hash plants. Trichomes are small glandular hairs containing plant resins which appear on the leaves and stems of the Cannabis plant.

Hash oil is a solution of tetrahydrocannabinol, but is a misnomer in suggesting any resemblance to hashish. It is made out of cannabis and is very potent due to its high THC concentration, which generally varies between 15 and 20%, but can reach 60 to 70% in some cases.
Usage

Hash oil is most often dropped on a cigarette or a joint, or it is mixed in food (such as space cakes or bhang).

Production

Hash oil is produced by allowing a solvent to dissolve the psychoactive cannabinoids that are present in marijuana. These cannabinoids remain behind when the solvent is subsequently evaporated, leaving a relatively pure, high-potency form of marijuana.The color and odor of the resulting extract will vary, depending on the type of solvent used. Current samples of hash oil, a viscous liquid ranging from amber to dark brown in color, average about 15 percent tetrahydrocannabinol.

Various solvents are suitable for the production of hash oil. Isopropyl alcohol, petroleum ether, and acetone are three commonly used solvents. Supercritical fluid extraction methods using various volatile compressed gases are also rumored to be used.

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 large volumes of butane gas, and the possibility of contaminants in the butane or the extraction vessel. BHO, or butane hash oil is a common term for the output produced by butane extraction of cannabis. "urging" of the product or further processing is highly suggested in order to remove any trapped butane/solvent(s).