Making an Absolute - Process, lessons learned, and recommendations

I admire your ambition and look forward to reading about the results. Otherwise, I have no experience or advice. I believe that many DIYers use the Steffan Arctander "bible" as a reference. Perhaps you might be able to upload the online copy.

I can imagine that it would work on marijuana just as well as any other botanical. Hexane is one of the most commonly used solvents for making concretes but it has a boiling point of 69°C, so the hexane is removed from the concrete with a vacuum pump to minimize the heat needed. Hexane comes in many grades, including food grade. Food grade hexane has had the benzene and toluene removed. Hexane is usually sold as a mixture of related hydrocarbons with similar boiling points, rather than isolated n-hexane.

It is necessary to use enough hexane to fully submerge the plant material. This is to insure that there is full contact with the solvent. The plant material used for making concretes is always fresh and undried. If the material is dense then grinding may be necessary for a full extraction. For a full extraction, the material must be soaked for several hours. The solution is then filtered and evaporated under vacuum.

After the concrete has been produced, it is dissolved in ethanol and refrigerated to around -20°C for 48 hours. This causes the waxes and fats to precipitate, which are then filtered out. The filtration takes place while the solution is still cold, to stop any lipids from redissolving. Lab grade filter paper such as Whatman #1 (11 µm) is sufficient for this purpose. For the home producer, good quality coffee filter paper may work instead.

Finally, the ethanol is removed under vacuum to produce the absolute. If you don't have a vacuum pump or you don't wish to buy one, then it's better to use a refigerant gas (hydrofluorocarbons, butane etc) to make the concrete, which boil off unaided. You can then dissolve the concrete in ethanol and rather than removing the ethanol, use it in solution as you would a tincture. I hope that this answered your questions.


Pears

Pears has given a splendid answer here already so I'll just caution on the safety aspects of doing this at home: beware that many of these solvents (including ethanol) are highly volatile and can form explosive mixtures with air. Combining these vapours with heat can be a very dangerous business, so please take great care that you know what you are doing and have either a sealed system or spark-proof ventilation or both before you start.

It was a good idea to mentioned that, Chris. It's important to follow the necessary safety protocols. Good ventilation is of paramount importance. If needs must, he can set everything up outdoors, weather permitting. Safety gloves would also be important, especially if handling refrigerant gases. I would detail a cheap and simple method for using refrigerant gases like butane but I think that he's more interested in using hexane.

- - - Updated - - -

I should add that sometimes it isn't necessary to convert a concrete into an absolute, it depends on the plant material, the solvent used and the extraction temperature. Some plant materials contain much lower levels of wax than others and don't produce concretes that are particularly waxy. If the solvent is very cold then it will also extract considerably less wax. This is one of the reasons why refrigerant gases are used. The other reason being that no heat or vacuum is required to remove the solvent.


A small home set up could be put together with a vacuum flask (thermos flask), a butane tank (or several butane canisters), some filter papers and a borosilicate glass collection dish. The reason for using a vacuum flask or thermos is that they keep refrigerant gases in liquid phase for several hours, at atmospheric pressure. This is why they are often used in labs to store liquid gases, such as liquid nitrogen.

I'm not suggesting that anyone do this themselves, I'm just describing how it could be done. As Chris stated earlier, it would be necessary to use caution and follow all of the safety protocols. Good ventilation, no ignition sources, protective gloves etc. Butane is highly flammable and for a home set up, it would be safer to evaporated it outdoors. The same would be true for alcohol, ofcourse.

I've been meaning to add to this post for some time, but I have just not had the time until now. Already you have several excellent replies from people more qualified than me on many fronts. What I can add is my own experience on making absolutes (actually I only went as far as a concrete, but essentially the same except for the last step) at home using hexane. The short answer is it is both expensive and dangerous to do this, but it is possible. I did it because I was in a place (Burma) where I did not have easy access to absolutes by conventional means and there were some flowers in my garden where absolutes simply did not exist. Also after having tried many other methods such as tincturing and becoming frustrated by the fact water builds up in alcohol when folding tinctures of flowers are made. And hexane was easy to buy. With varying success, I made a concrete of 4 different things: 1) Gardenia, 2) a small indolic flower I don't know the English name of 3) Oakmoss, 4) Frangipani

In all but the case of the Frangipani I used small amounts of hexane (1 liter). For Frangipani I used 5 liters of hexane (and 5 times more flowers). On advice from this forum I proceeded by picking fresh flowers every day putting them in the hexane overnight, draining/filtering the the next day and putting in new flowers in order to saturate the hexane as much as possible. (you need two containers, in order to pour from one to the other and back. I would clean the alternate container completely after each day). This was the main process. I did this without any scientific way of telling them the Hexane was fully saturated. In the case of Gardenia I ran out of flowers as the season was shorter than my patience. The other limiting factor of this method is hexane loss, as some clings to the flowers each time they are discarded. This is unfortunate as you are losing both nice saturated hexane you have worked to hard to get and also the hexane itself, at $10/ Liter was being lost). A solution to this would be squeezing them out, but I wanted as little contact with the hexane as possible so I let the drip, sitting in a funnel, to get as much as possible, but far from ideal. I disposed of the toxic waste spent flowers by laying them out in the sun on the pavement to burn off as much hexane as possible before adding them to the gardener's "to burn" pile of organics. Also of note: some flowers (Gardenia and Frangipani) are quite "fat" and contain a lot of water, and small deposits of water developed in the bottom of the hexane containers. I used a pipette to remove this everyday once I realized it would contaminate the mix with potentially rancid water full of organics. Once complete I filtered the hexane solution through lab filter paper two or three times. The next step would be to run it through a rotary evaporator to both re-capture the hexane for later use and to separate out the concrete at a low boiling temperature. Unfortunately I did not have this. I consulted a friend who used to work in a traditional medicine extracting lab (hoping I could borrow a rotovap) and he said a group of Japanese technicians had the same problem, wanting to extract coffee flower concrete for their personal use. The low tech, and not ideal, solution offered to me was: Get a large beaker (the beaker spout is important as you will see in a moment), boil water far from your hexane and bring the pan to the beaker, now filled with your saturated hexane. Put the beaker in the pan of hot water (as in a double boiler). Put a plate or bowl over the beaker and fill this (plate or bowl) with cold water. Reheat the water as many times as necessary until all the hexane is out. The idea here I think is that the volatiles from the plants will stay mostly in the container and the hexane, being more volatile, will slowly bleed off into the atmosphere through the beaker spout. I did this outside as you can imagine due to the fact Hexane gassing off in the house is not a great idea on many fronts. This method has many drawbacks, from losing nice smelly volatiles, to the whole thing after weeks of work getting knocked over by the dog (or in the case of my garden in Burma, God knows what pythons, palm civets etc.) to the fact without a vacuum you will never really get all the hexane out and traces will remain. It also took an incredible amount of time this way. In the end, running out of patience, I got an extension cord and put the pan of water directly on an electric burner at low power (with the beaker in it still as in a double boiler of course). Nothing blew up (this is no guarantee it might not for you...). When handling Hexane I thought of it as gasoline in terms of danger and volatility. I also found the plate on top of the beaker to make the process take seemingly forever, and so I arrived at a compromise of doing it with the plate on for about 80% reduction, and the rest fully open, knowing I was losing precious smells, but really no choice unless I wanted it to take days. The results were really tiny amounts of some pretty nice stuff: from the 1 liter gardenia I got about 1 ml of nice goo, and from the 5 liters of frangipani about 10 mls of a very true to life (VERY sticky) concrete (which cost me $50 for the hexane alone, not to mention all the labor, equipment and electricity). Oakmoss was less of a success, I think I will go with a soxhlet extraction in ethanol directly next time (oh and the oakmoss was from my home in France, I brought it back to Burma to play with --in case anyone though I was saying there is oakmoss in Burma) The next step to make an absolute is to stir up the concrete in ethanol and then rotovap out the ethanol to get an absolute. This is (mostly) unnecessary for personal use (and I had no way of doing it anyway) and I just mixed the concrete in ethanol and filtered (many weeks later) and keep the ethanol concrete "tincture" for use directly as is. It was messy, time consuming, hard, dangerous and expensive, but I have moved from Burma now, and I treasure these concretes more than almost anything in my collection.

I am not recommending anyone replicate what I did, but hopefully me experience will help others.

gecko214, that sounds like such hard work, but highly entertaining, thank you so much for sharing!

I enjoyed reading your post, gecko214. Thank you.

That was an interesting read, gecko. Evaporation of hexane or alcohol is indeed difficult without a vacuum pump. I'll run through one of the more basic methods that I have used in the past to produce concretes, without the addition of any heat. The key is in selecting the right solvent for the job. Butane is a simple alkane, like hexane but boils at -0.5°C and it can therefore be removed from the concrete without the addition of heat or a vacuum.

Method:

1) Loosly fill a 1 liter stainless steel thermos flask with fresh, separated but unground botanicals.
2) Place the thermos flask in a freezer overnight, along with three canisters of high purity butane lighter refill (Colibri, Newport, Vector etc.)
3) Remove from the freezer and take outdoors, for good ventilation.
4) Place a metal jar lid with a puncture hole in the centre, over the mouth of the thermos flask.
5) Put on protective gloves, as a precaution.
6) Insert the nozzle of the butane canister into the hole in the lid and inject the butane down into the thermos flask. Repeat with second canister and the third if necessary. The botanicals must be fully submerged in the butane. After inspection, place the jar lid back on loosely.
7) Leave the thermos flask to sit in the shade for 2 hours or more, sheltered from wind.
8) Slowly pour the butane through a fine stainless steel strainer, into a borosilicate glass, pyrex or stainless steel dish.
9) Leave the butane to evaporate in the dish for about half an hour or so, or until only a viscous or solid residue remains.
10) Bring indoors and leave to finish curing at room temperature for atleast 24 hours.
11) Scrape up the cured concrete from the dish and place in suitable glass vessels. You have now produced a high quality concrete, undegraded by any heat.

Optional extra:

12) Dissolve the concrete in ethanol, refrigerate at -18°C or lower for 24-48 hours (winterization) and filter out the wax/fats with lab grade filter paper or coffee filter paper. Bottle and use as a winterized tincture.


Important: Do not attempt solvent extractions unless you understand all of necessary safety protocols.

What about a hand vacuum pump?

I bought one on ebay a few years back...

Gecko: It's too bad you're not close to So California, I've been itching to get my rotovap up and running to do something with it...

The butane extraction method sounds interesting, but isn't ethyl mercaptan usually added to make it smell like 'gas'?

-

- - - Updated - - -


A hand vacuum pump should work, but you'll have to keep pumping. You might like to apply a little heat to help things along - a warm water bath (NO FLAMES!!!) would be ideal - but there are complications...

The normal procedure for boiling under vacuum is to lower the pressure first, then control boiling using the heat source. But as you're using a hand pump the pressure will vary (unless your pump has a regulator) so the boiling point will vary. This can lead to gentle simmering suddenly switching to instant vaporisation in your vacuum vessel, and all your liquid - including the things you want to keep - ending up in your pump. An air leak line into the liquid might help here, but I'm guaranteeing NOTHING...

And don't forget that you'll have inflammable vapour flowing through your pump.

-

Hi Skelly, yes it is often added to larger tanks intended for cooking or heating, to aid in the detection of gas leaks. Some of the cheaper butane lighter refill canisters contain this butane aswel. However, the higher end butane lighter refills tend to use butane without any ethyl mercaptan added. The brands that you should look out for are Colibri, Newport, Vector, London and any other brand that states that it is triple refined or more, or has the "Near Zero Impurities" logo on the can.

It does work with dried plant material aswel but absolutes have historically been made from concretes rather than oleoresins. Concretes are extracted from fresh plant material with non-polar solvents. They are often favored in the perfume industry because of their fresher aroma but the non-polar solvents used to make concretes extract alot of plant waxes. These waxes don't dissolve in alcohol or water so they are removed before the extract is added to fragrances. There is no reason why you can't make an oleoresin from dried material and then make an alcohol extraction. It just wouldn't technically be called an absolute.


It can be re-used but if you notice any unwanted aroma in the hexane, you can fractionally distill it. You should know how to do that with your chemistry background. If you wish to recapture butane, you will need a spare gas tank and a pump but it's complicated. Alternatively, you can pour the butane from one thermos onto fresh plant material in a second pre-chilled thermos.


That's correct, it is to protect the more delicate aromas from deterioration. I hope that this has helped to answer your questions.

Pears

Ksennish, if you choose to use dry plant material, you can grind it up before extracting with butane. You wouldn't want to grind up fresh, water rich plant material when using butane because the butane would freeze it together in a clump and prevent extraction. If you grind up the dry material, you'll need to filter through lab or coffee filter paper. If you don't have a stainless steel or lab glass funnel, you can fashion a filter holder by bending a wire coat hanger into a loop with a handle and then fit the filter paper into the loop and clamp it around the edges with some clothes pegs.