Extraction & Purification of Marijuana & Hashish Oils
Step 1: Preparing the marijuana or hashish
If marijuana is to be used as a starting material, the seeds are removed prior to extraction. The remaining material is them crumbled or broken and the stems cut short with scissors. The marijuana is dried thoroughly. An oven is preheated to 250°F and turned off. The marijuana is placed on a cookie sheet for fifteen minute intervals until the loose leaf and flower parts may be easily crumbled to powder between the palms. This procedure prevents scorching the plant.
Hashish may be heated for several minutes in an oven or in a frying pan at low heat until it begins to smoke slightly. It is then easily crumbled in the hands, or, if a mortar and pestle is available, it may be ground to a fine powder. Powdered hashish exposed to the air for long periods will decrease in potency, so this grinding is done just prior to extraction.
Step 2: Pulverizing the cannabis material
There are several reasons for reducing the material to the finest powder possible. Ruptured cell walls allow the oil to be extracted more readily and the volume of the starting material is reduced, thus lessening the size of the extraction apparatus needed, as well as the amount of solvent required.
Marijuana is put into a heavy-duty blender until it is one-third full. A slower speed allows the ground material to fall into the blades while constantly flowing up the sides from the bottom. If necessary, the material can be agitated with a wooden stick while the blender is not running. It is dangerous to stir while the blender is operating, as the stick can be shot from the blender with great force. It is easier to grind the chopped stems separately and then mix the powdered material before proceeding to the next step.
Hashish may also be ground in a blender, but small amounts should be run, as larger amounts will put a strain on the motor. Pressed forms of hashish may be shredded with a cheese grater prior to blending.
Step 3: Refluxing
The essential oil is extracted from the cannabis material by refluxing (boiling) in a solvent. This essential oil (containing THC and related substances, chlorophyll, and the substances which contribute the taste and smell) dissolves in the solvent (usually an alcohol), while the cellulose parts of the herb do not dissolve. The leached marijuana is removed by straining, and the solvent containing the oil is evaporated, leaving as residue the essential oil of the herb.
As it is very dangerous to boil solvents (the fumes and liquid are quite flammable), it is necessary to use specialized methods in order to perform the operation safely. Refluxing apparatus is composed of the following items:
1. A small pot, preferably of stainless steel, to hold the powdered cannabis material and solvent. The pot should not be over two-thirds full when the marijuana is covered with half again its volume of solvent.
2. A large stew pot with lid at least fifty per cent wider and twice as deep as the smaller pot mentioned above. Both pots should have flat bottoms.
3. A large, deep tub for boiling water, at least twice as wide as the stew pot.
4. A heavy-duty electric hotplate with two burners.
5. Several yards of one-inch hemp or manila rope.
6. Large, thick polyethylene trash bags. Three-mil-thick trash bags are best.
7. Innertube cut into one-inch-wide rubber bands to fit tightly around the stew pot.
The large tub is placed securely on the hotplate. Lengths of one inch rope are then placed in the bottom of the large tub to keep the stew pot (set in the tub on top of the rope) from resting directly on the bottom of the tub. The small stainless-steel pot containing the powdered cannabis and solvent is placed in the stew pot, and the lid is placed on top of the stew pot in an inverted position (upside down). A piece of plastic trash bag is cut and placed over the lid of the large stew pot so that it extends halfway down the side. The unit is sealed by securing the polyethylene sheet to the stew pot with two large innertube rubber bands. The innertube bands are positioned several inches down the side of the pot, allowing some slack in the plastic sheeting. Any air that is trapped under the plastic is forced out by loosening the rubber bands and flattening the bag with the hand. As much ice as possible is piled on the plastic bag covering the inverted lid of the stew pot. The tub is filled half full of water which is then brought to a boil. This heats the apparatus to about 212°F, but not above.
As the stainless-steel pot containing the cannabis and solvent is heated by boiling water in the tub, the solvent boils. As the fumes rise inside the apparatus, they make contact with the inverted lid of the stew pot, which is cooled by ice from above. These fumes of solvent then condense to liquid, relieving the pressure created by boiling, and drop off the inverted lid back into the stainless-steel pot containing the cannabis and solvent. By refluxing in this manner, there is no danger of explosion or of toxic fumes escaping into the air.
The reason that the cannabis and solvent are not put directly into the large stew pot is that the condensing surface area (the ice-cooled lid) must be larger than the surface area of the boiling solution in the stainless-steel pot.
The plastic sheeting is used for several reasons. The reaction is completely sealed from the atmosphere, preventing any fumes from escaping or igniting. A rigid seal, such as the locking top of a pressure cooker, is not good, as it would prevent pressure buildup in the stew pot from causing the plastic bag to inflate. The inflation of the plastic notifies the chemist of the pressure increase and also causes the ice to fall into the boiling water bath, cooling the rig to a safe temperature and reducing pressure within the system. Pressure will not build up too high unless one neglects to keep enough ice on top or allows the apparatus to heat up too fast before the ice has sufficiently cooled the inverted lid. Refluxing is done for three or four hours. Most of the essential oils of the cannabis material are now dissolved in the solvent.
There are several solvents that work well. Their properties, and the advantages and disadvantages of each, are discussed below:
1. Methyl alcohol, methanol, wood alcohol (boiling point 64°C). This solvent is commonly employed and, if used correctly, does a fine job. Methanol is available at many pharmacies and in larger quantities at industrial chemical supply companies. It is also available as paint thinner, but it is seldom very pure in this form. Methanol fumes are toxic and explosive. Inhalation of these fumes makes one sick, with pronounced body ache. Continued inhalation of 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 a uniform temperature (approximately 190°F) and does not extract a lot of the water-soluble tars, which are not psychoactive. A method for removing traces of the solvent will be discussed later.
2. Rubbing alcohol (most rubbing alcohol is 70% isopropyl alcohol and 30% water). There are several advantages to using isopropyl rubbing alcohol. It is available in many stores at a low price and is much less toxic and explosive than methanol. Unfortunately, because it contains water, many of the watersoluble, non-psychoactive substances are also extracted. The oil yield using rubbing alcohol is twice that of methanol, and is proportionally less potent. Water-soluble tars may also give the oil undesirable taste and burning qualities. If the oil is to be reextracted later with a more selective solvent, however, it matters little what it is like at this point. The water in the mixture also causes it to evaporate at a much higher temperature than methanol. Once the alcohol is completely evaporated, the water that was in the solvent remains with the oil. This takes a long time to evaporate in a boiling water bath. An oil bath may be used. The temperature of the oil in the bath is kept slightly higher than the boiling point of water. Water that gets into the oil bath may spatter; this is a hazard.
3. Ethanol, ethyl alcohol, pure grain alcohol (boiling point 78.5°C). This is a very desirable solvent. It has extraction properties very similar to methanol, but is not as toxic. It is very difficult to obtain, however, as it is a major active ingredient in liquor and is heavily taxed. Pure ethanol may be produced from either liquor or fermented material. Denatured ethanol, which is available in hardware stores and pharmacies, contains non-removable poisons which evaporate at the same temperature as pure ethanol. This makes the ethanol unfit for drinking.
4. Petroleum ether (boiling point 30—60° C). Petroleum ether is a light solvent 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 ether but, due to petroleum ether’s highly explosive nature, the oil is first removed from the plant material with alcohol and then reextracted with ether.
This requires a much smaller amount of the dangerous solvent. Petroleum ether is usually available only through chemical supply companies.
Step 4: Soxhleting
After refluxing, it is necessary to remove the oil bearing solvent that still remains in the expended cannabis material. This is done by draining the dark oil/solvent liquid from the cannabis material and washing the material repeatedly with clean solvent. A vegetable-draining colander is placed above the stainless-steel pot mentioned before. The colander is fitted with a large coffee filter paper (twelve-inch David Douglas brand papers are quite adequate) and the cannabis/solvent/oil mixture is poured into the colander. The oil bearing, dark-colored solvent/oil mixture drains from the bottom of the colander, free from particles of vegetable matter. The colander is then set on top of the stainless steel pot, now containing the alcohol/cannabis-oil solution, and the apparatus is reassembled in the same manner as for refluxing.
As the solvent/cannabis-oil solution boils, the alcohol fumes rise until they meet the ice-cooled lid and recondense into liquid. The oil does not evaporate and remains in the stainless-steel pot. The drops of pure, recondensed solvent fall from the ice-cooled lid and drip through the colander containing the cannabis material. The oil remaining in the cannabis material is washed out and drains into the stainless steel pot. The oil is totally extracted when several drops of the liquid draining from the colander leave no colored residue when evaporated on a piece of glass. Before opening the apparatus after soxhleting, the rig is cooled sufficiently to condense any fumes. Setting the stew pot in a tub of ice and water for several minutes is one method of doing this. A thick blanket can be kept soaking in the tub. This is an excellent safety measure, since a water-soaked blanket is an excellent fire extinguisher.
Step 5: Removal of the solvent from the oil
To distill off the solvent, a small collection pan replaces the expended cannabis material in the colander (which may be discarded). The apparatus is then reassembled and returned to the water bath. The solvent/ oil solution in the small stainless-steel pot boils; the fumes rise and are condensed on the ice-cooled lid as before. The pure solvent drips into the colander, where it is collected in the small pan. The oil remains behind in the stainless-steel pot. The collected solvent, which is essentially pure, may be saved for a future extraction.
After the solvent is removed and collected, the stainless-steel pot containing the oil is kept in boiling water to remove all traces of the solvent. If a toxic solvent, or one containing water is used, steps are taken to remove the last traces of solvent and water. Some water is added to the oil and evaporated in an oil bath (cottonseed oil works fine) at approximately 220°F. When the water is gone, all traces of the solvent have been removed, since all solvents mentioned here evaporate at a temperature below that of boiling water. The oil may now be eaten or smoked.
Step 6: Purification
Oil produced using this method is quite potent, but still contains substances which give the oil its taste, smell, and color. These are sometimes very pleasant to smoke, and they are sometimes left in the oil. Removing them, however, greatly increases the potency, but decreases the yield proportionally.
The oil from the extraction is dissolved in five times its weight of alcohol and poured into an equal volume of water in a large glass jug with a screw-on cap. All solvents used are cold or cool. A volume of petroleum ether equal to half the volume of the water used is added. The screw top is tightened and the jug is inverted. The jug is turned upright immediately, and a few seconds later, when the mixture has run down the sides of the jug, the screw cap is opened slowly to relieve the pressure. The inversion of the jug is repeated about twenty-five times, which releases the pressure each time, and then the jug is allowed to sit for about half an hour. The mixture of liquids will separate into three distinct layers. The bottom layer will contain water, alcohol, and the substances in the oil (tars and resins) that are not soluble in petroleum ether. The thin middle layer is an emulsion of waxes, ether, and air bubbles. The top layer is the purified oil dissolved in petroleum ether.
The jug is fitted with a two-holed rubber stopper, glass tubing, and rubber hose. Two pieces of glass tubing are fitted into the two-holed rubber stopper. (Injuries when cutting and fitting glass tubing are frequent—cut ends are always fire-polished and hands must be protected when any force is used in fitting the tubing.) One piece of tubing need only protrude from the stopper an inch on each side. The other tube is positioned so that when the stopper is tightly fitted to the jug, the tube extends into the mixture to a half-inch from the bottom of the ether/oil layer. The other end of the tube is attached to a length of rubber tubing to transfer the ether/oil solution to a collection jug. The end of the tubing must be lower than the end of the tube in the ether/oil solution in order to obtain a siphon action. A short piece of rubber tubing is fitted to the short glass tube, and air pressure is applied to start the siphon. The glass tube is spaced a bit above the emulsion layer; any ether/oil solution not removed will be recovered later. The ether/oil solution in the collection jug is saved. Another volume of fresh petroleum ether is added to the extraction by inverting, separating, and collecting the ether solution, which is added to the first ether/oil solution. This process is repeated until the ether layer remains clear after inverting. This indicates that the ether-soluble oil is totally extracted from the alcohol-and-water layer. No more than several ounces of the combined ether/oil solution is put in the stainless-steel pot, and the collection pan is placed in the colander. The apparatus is reassembled, as was done for the removal of the solvent from the oil after soxhleting. The rig is placed in the water bath and slowly heated to 140°F. After evaporating and collecting the ether (saved for future use), the stainless-steel pot with the oil is put into a boiling water bath for several minutes and stirred occasionally to remove any residual traces of solvent. The refined oil thus obtained is much superior to the oil obtained from the original alcohol extraction.