Rotary Evaporators

Rotary evaporators are one of the ways that fractional components can be distilled out of a solvent mixture, while minimizing heat input.

In is simplest form, rotary evaporation is a boiling flask of solution is rotated on its side in a hot bath, while under vacuum, with the vapors being condensed and collected using a chilled heat exchanger.

The rotation coats the inside of the boiling flask with a thin film, greatly enhancing film surface area and evaporation rates.

Using vacuum instead of heat also allows fractionally distilling fragile substances sensitive to heat, such as carboxylic acids.

By controlling the heat and vacuum level, individual fractions may be distilled off and collected at their different boiling points.

There is more than one company manufacturing lab size rotary evaporators, and the cheapest is not inexpensive, sooo we’uns decided to attempt a comparison of available offerings, to share with ya’ll.

Not just what is available, and what does it cost, but what is the utility at the margin, aka bang for the buck, because they also range in price.

One out of three success from our first round of importuning central suppliers for the loan of a test unit for impartial-pari-passu (IPP) (even, same/same, side by side) comparison with their competition, to share with our readership.

Hee, hee, hee, snicker, snark, snort, I’m pleased to report that Heidolph is proud and confident enough of their Hei-VAP Precision ML G3, to supply it and a chiller for our trials and sooooo, we’uns have been having our way with her at the Pharm.

She is a gaugus piece of precision equipment from zee fatherland, who gets extra points for being purdy to gaze longingly upon, but more importantly, she has been reliable and a joy to operate. A admirable quality that lingers in mah heart, after the honeymoon is over and the joy of her good looks wanes!!

More fractional distillation experiments underway, but check out Jules report on ethanol removal using the Heidolph Hei-VAP Precision ML G3 at:

Thank you Jules from Specialized Formulation’s for conducting the tests, as well as Rick from Botanical Analytics for lab space, and support.

Thank you Heidolph for sharing the ML G3’s charms with us’ns and readership! We admire manufacturers who are confident enough in their equipment to belly up to the bar for unbiased IPP comparison

We also still have offers out to other manufacturers, and if any more decide to join us at the bar to strut their stuff, we will share that as well.

Lu lu lu lu lu lu lu lu lu lu lu, let the fun begin!!

15 responses to this post.

  1. Posted by joey on September 25, 2016 at 8:23 PM

    so if im reading this right I can just add certain glass to my 2L rotary evaporator to do fractional distillation?

    also have you ever considered doing a write up on how to do proper lractional distillation? i have all the glass, pump, plenty of extract but im just a patient i have no channels to ever find out other than some $5,000 class. lol.



  2. May i know how large size they can do at Heidolph company ?

    Kori instrument Co.,Ltd is also specilizing in rotary evaporators and glass reactors manufacturing .


  3. Posted by redturtle984 on June 30, 2016 at 1:47 PM

    Another way to separate dispensary extracts or at least remove respiratory irritants is to remove as much alpha pinene as possible. This is done with isopropyl alcohol by disolving the extract first in iso, then adding the iso to water. The alpha pinene is partially soluable in water and rolls right out of the mix. It is easily seaparated and the flavor of the oil that rrsults when it is dried of moisture is exquisite.

    here is what the step,to remove pinene looks like. Two centrifuge tubes that have been used to dewax the iso/extract are then added to a makeshift separatory funnel and you can see indeed that water serves an excellent prupose inpurifying raw dispensary extract.

    This process does not replace fractioning in an evaporator but rather is one metheod to remove enough non medicine from the xtract to get to nearly pure but without losing the entire terp profile, plis the added benefit that anyone can do it. Moreover, those who are running a rotary evaporator can substantially increase priduction by first removing the alpha pinene in a bulk manner rather than through evaporation Alpha pinene smells horrible and makes me hack and choke. Irregardless of marketing hupe, most terps if not being described by a marijuanna enthusiast are called “industrial solvents”. I choose to remove the solvents from my extract – even the ones that occur naturally.


  4. Posted by weeddeliverynearme on June 21, 2016 at 3:24 PM

    The Hei-VAP Precision ML G3, recovered 11ml per minute. How does that compare to the diy rotovap made here on skunk? When comparing prices it would be good to know how much better this is vs diy roto and also vs a 100$ normal lab distillation rig with magnetic stirring and vaccume. I think if you use the correct paddle inside the flask. The magnetic stirrer can do what a rotovap does but with no rotation of the flask. Just the liquid inside.


    • Posted by redturtle984 on June 22, 2016 at 5:20 AM

      The comparisons between the various separation methods available are generally irrelavent as a practical matter. I routinely boil extracts from dispensary sources in a small beaker or flask. It is easy to boil off however much a person might want to. The first little bit smells absolutely repugnant and causes harsh stinging to the eyes and throat when sample over the beaker as it comes off, but when the vapor starts smelling sweet I stop the boil and dewax in the same beaker.

      I could say my rig is a $6, 50mL beaker and that I fraction off the a-pinene and I would be correct. But my needs dictate the method. I need only personal use medication produced, so waiting over a 50mL beaker for raw extract to turn sweet is wihin the time domain and production needs that I have.

      A rotary evaporator would cut my processing of my meds considerably because the key advantage of the rotary portion is increased surface area, therefor increased evaporation potential and increased production. Stirring bar likely woild increase production for me somewhat too, but not by increasing evaporation area. I could heat the mix more rapidly without hand stirring is about it. Obviously the expense of equipment versus production needs are the issue. Simple question; how many grams or mililiters do you need to produce per hour? The answer dictates the solution used.

      I use a 35W sealed light in a metal base as a heat source. It easily gets the mix up to 360F which is where it stays while slowly evaporating off. Add a vacuum and I could reduce the temp, and time too, but again this is a matter of production needs. In my process I use a very high vacuum for a specific purpose but my own purpose is purely hobby in this regard. I like making hash oil and I simply cannot obtain oil like this without making it from extracts like I do. Once you sample good red oil…there is no turning back Bilbo….you will not be the same Hobbit you were.

      At any rate here is a vid of a small boil for last months med. The resulting oil is liquid at room temp, vapes velvet smooth in my vape pen as pure oil (NO GLYCOL or anything), and I can prepare a whole month supply in about three or four hours.


  5. Posted by redturtle984 on May 14, 2016 at 9:15 PM

    I have discovered a method that fractionalizes dispensary extract holding temperatures at or below 100 C, and uses only water as a the media for separation. I only operate on a hobby level, but the technique requires no special equipment. Currently as far as I can see the method will only work on extract that has not yet been decarboxylated as it relies of the fact that extract in raw form will sink in H2O, but extract that is in the process of decarboxylating becomes bouyant in water during the time period that it is undergoing decarboxylation.

    The setup it very simple really, and it wiil put to bed the idea that components of the extract are not water soluable. I am not a lab so my testing is visual and personal usage of product, but with no doubt at all there are components that can be separated easily if the correct setup is employed. Zero solvent beyond H2O is indeed possible and the simplistic nature of the setup makes it easy to do by anyone capable of safely handling boiling water can handle easily.

    Since I have only used the process on less than 1/4 ounce of extract at a time I have no idea if it can be scaled up, but the advantage is that during separation like this there is nothing required except a stove top, minimal glassware, and no high vacuum or anything other than gentle heat and water at ambient temps. And time. The disadvantage of my process is that it depends upon decarboxylation to occur during the heating process to substantially work, but it will break the extract down into the major components for either immediate usage or further processing. I use it to remove waxes and irritants and the process is hands down the best method I have used to produce pristine extracts from dispensary grade. The process will fully decarboxylate the extract but will do so without the presence of oxygen to the greatest degree a hobbyist can achieve.

    Water by itself with some gentle heating and the right glass setup (one test tube, one boiling pan, glass stir rod, stands, heating element) does indeed fractionalize dispensary extract. I vaped some this afternoon. Smooth as silk inhaling. Peace from Oregon.


    • Posted by redturtle984 on May 15, 2016 at 12:34 PM

      • Posted by joey on September 25, 2016 at 8:21 PM

        whats the process after you pull it from the test tube? awesome work!!


        • Posted by redturtle984 on September 28, 2016 at 3:06 AM

          I have many ways to dry out extract for vaping but always come back to a rubbing alcohol wash. Using tthe unique polarity and properties of isopropyl alcohol and water which forms an azeotrope, it is simple to wash the extract in RA then evap,with just a fan blowing across the surface. This will evap down and break the azeotrope between the water and isopropyl alcohol. A milky white water residue separates from the mix as it evaps, which is the water and mostly pinene that have become immiscible in the extract and is easy to pour off.

          At that point just a rinse in tap water renders it safe for vaping but to prevent popping in a dab rig a trip into the vac chamber will pop out any bubbles.

          Also, a strong pin stirred BRISKLY through the extract after the water will work out the vast majority of water bubbles. As you stir you will feel the water pop out of the much thicker extract and sprinkle your hand and spatter your face. The wire traps the water bubbles in the harder oil as you stir and it has nowhere to go but pop.

          Finally, there is a final technique that requires flame to remove Volitile Organic Compounds using a few milliliters of rubbing alcohol to ignite the VOCs (terpenes). This site for safety reasons has asked me not to post examples of using flame to remove volitile organic compounds from the extract, but
          i will say that once you sample oil with the volitiles flamed off you will not want to go back to vaping them again – no more burn or hack and choke.

          Smoking eiher flower or extract automatically burns them off – the advent of vaping prevents combustion of the natural solvents (terpenes), so extract that is not treated with flame is providing a concentration of natural solvents not normally experienced by those who use flame to smoke it. Pure thc is very hard to detect as a vapor in my lungs and is sweet. It certainly does not cause me to hack and choke with even fog like density, so I deem it of great persinal value to remove the terps, which in other industries are known as Volitile
          Organic Compounds and for products meant for ingestion these elements are generally removed. VOCs are the building blocks of global warming if you believe in that hoopla as well

          I applaud SkunkPharms committment to safety, and while I believe that over the years my method of purifying as described can be done safely, I support and complement the team on their approach to safety and will honor their request to exclude details of using the flame tehnique.

          I have a blog website that will start to showcase for he hobbyist a great many ways to produce light yellow clear and chalky nearly pure thc with normal kitchen or inexpensive hobbyist stuff.

          Thank you for the compliment.


  6. This looks great…but i am a commercial grower in wa state. Do they have this model in a larger size? To be able to process 5 gallons of solvent at a time. Prob not huh. Looks pretty cool for the home master batcher though.

    My ;


  7. Posted by Suzanne on December 17, 2015 at 11:31 AM

    This looks great…but i am a commercial grower in wa state. Do they have this model in a larger size? To be able to process 5 gallons of solvent at a time. Prob not huh. Looks pretty cool for the home master batcher though.


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