Frequently Asked Questions

In regards to the rapidly evolving marijuana industry and the associated cannabis distillation process, there are a multitude of questions being asked. While some people may know all about distilled THC extract, they may not realize the benefits of a fractional distillation machine.

Below are a few questions recently posed to us and the answers we hope will enlighten you as much to the process as to Pope Scientific.

1. Where are Pope Scientific’s distillation systems manufactured?

At Pope’s plant in Saukville, (near Milwaukee) Wisconsin, USA. The equipment is made, fully tested and serviced in our facility, and nearly every subcomponent is likewise of domestic origin. Spare or additional parts are normally available overnight to locations throughout North America, and within 2-3 days to most other countries worldwide.


2. What is the purpose of this equipment?

Extraction can only go so far in purifying of cannabinoids such as THC and CDB. So a different technique is needed for increasing purity. A thermal separation technique works well at this point because cannabinoids have a different boiling point range than other materials in the extraction mixture. Molecular (short-path) distillation is the best thermal separation method for this heat-sensitive material because it is the gentlest type, causing the least amount of thermal degradation of product.


3. Is molecular distillation similar to extraction?

No, they are quite different operations. With extraction, solids, (or sometimes liquids) are brought into contact with a solvent. In cannabinoid work, the solvent is typically ethanol, or butane/propane, or supercritical pressurized CO2, or others. Certain compounds such as cannabinoids, terpenes, chlorophyll are dissolved into the solvent, after which the solvent is evaporated away. The separation is accomplished via an affinity of the target compounds to be transferred by dissolution into the solvent. With distillation, the separation is carried out not by solvent affinity, but by differences in the volatility (boiling points), between the various com pounds. More volatile materials are more easily distilled and condensed as distillate while the heavier materials remain as liquid collected as residue. Distillation is performed after extraction to further concentrate and purify the desired compounds.


4. What level of purity is expected with the Pope stills?

It depends on the quality and composition of the feed material, factors going back to the original plant strains plus all subsequent handling and processing prior to distillation. Often, extracted material prior to distillation is in a range of 55-70% cannabinoid, and it is typical to distill this up to a range from 85-90+%, with up to 96% being reported. In addition to increased percentage purity, the product is significantly lighter yellow in color, with high clarity.


5. Does molecular distillation require addition of solvents?

No, additional solvents or other compounds do not need to be added to the feed material. This question often arises because potential users know that concentrate from extraction can be quite thick and viscous. But rather than using “thinning agents” such as solvents, the high viscosity or melting point of cannabinoids is handled by keeping materials warm enough to flow throughout the entire set of distillation components. Equipment needed for these heating functions is provided in the Pope still systems configured for cannabinoid applications – there is nothing else needed to buy.


6. What is the difference between Pope’s wiped film molecular still (WFMS) and a short-path still or a fractional still?

There seems to be a lot of confusion and misuse of terminology in this type of equipment. So, below are some points to keep in mind:

A. Molecular distillation is the same thing as short-path distillation. These both imply use of high vacuum and a condensing surface in close proximity to a heated evaporation surface. For many applications such as cannabinoids and other compounds with even greater molecular weight and boiling points, if this distance is not close, the equipment will not work well, if at all.

B. Some people associate the term “short-path” only with a basic glassware setup involving a basic boiling flask with a neck leading to a condenser and a receiver flask(s), or else a similar variation called a KIugelrohr. These are also referred to as pot stills, (in the vessel, not marijuana sense), and are all considered batch mode apparatus. But these are only one type (and the simplest) of short-path or molecular still – there are other forms, including Pope’s continuous mode WFMS.

C. Molecular stills are not fractional stills. Fractional still equipment implies utilization of a vertical packed column providing multiple equilibrium stages or “theoretical plates”, requiring the condenser to be further away from the boiling flask and reached only after the sometimes quite long obstacle of the packed column, a problem for heat sensitive materials such as cannabinoids. The single theoretical plate of molecular stills is sufficient for most cannabinoid work and offers the least product degradation (Pope does offer fractional distillation equipment of several different types and size ranges for other applications).


7. So what is the advantage of a Pope WFMS over a basic boiling flask type molecular short-path still?

There are several, including:

A. The WFMS is a continuous mode, rather than a batch mode still. This means that with larger or special flasks, or with liquid pumps, they can operate for extended periods of time with any quantity of feed material and with the same consistent product composition over time. The WFMS is also scalable, such that when much larger quantities of material needs to be processed, larger versions of the same type of equipment can be utilized to accommodate the greater throughputs required. Batch mode stills such as the BFMS are very limited in scalability.

B. The WFMS offers much less thermal degradation and greater product purity and yield because of: i) a very short residence exposure time to a heated surface – only a matter of seconds, compared to many hours in a BFMS, and ii) a highly efficient dynamic rotating wiped film action providing turbulent moving thin film mixing compared to the limited, less dynamic liquid/vapor interface of simple boiling flask apparatus.


8. How is the distillation carried out?

There are normally two (or more) passes made through the Pope still. The first is to remove whatever amount of remaining air, gas, water, solvents and lighter end terpenes remain in the extract. The second, carried out at greater vacuum and temperature, is normally for distillation of the cannabinoids away from the heavier residue including chlorophyll, heavier waxes, sugars, salts, pesticides, dark colored components and other undesired matter. Without the first devolatilization pass, the cannabinoid distillation will be slower and not be as successful because the vacuum obtained will be weaker and microflashing of gasses and volatiles will physically carry some undesired compounds and colors over to the distillate product. There are also additional distillation strategies which are covered in training at Pope.


9. Is extreme vacuum level and capacity required?

No, in fact, very high vacuum level in the evaporator body is not even attainable because of the vapor pressure/temperature properties of cannabinoids. At the typical body temperature range of 130 – 180°C, the vacuum range observed is normally roughly around 0.1 to 0.3 torr, no matter what kind of vacuum pump is utilized. Pope mounts the vacuum sensors on the vacuum arms of still bodies, as close to the process as possible, where more meaningful, useful and accurate readings are obtained. Some people have mentioned to us that their experience has been that much greater vacuum levels had been observed and required with various equipment they have used. However, in those situations, the sensors have typically been mounted directly near the inlet to vacuum pumps where an optimistic reading is observed. By that point, vapors will have been collapsed and condensed on internal and/or external condensers plus a very low temperature cold trap, resulting in magnitudes less numbers of molecules per volume at the sensor – the factor that actually defines vacuum level! Pope’s molecular still competitors normally likewise mount their sensors near the vacuum pump inlet – the higher vacuum levels these may read are indicative of nothing other than sensor placement. Our molecular stills are capable of true body vacuum levels of better than 0.001 torr – when the materials being processed possess very low vapor pressure and much greater boiling points and molecular weights than cannabinoids. Sometimes, clients prefer to use very high capacity (>15 CFM) vacuum pumps as well, in the thought that these will perform better than the ones Pope provides as standard, however, these are also not necessary for reasons similar as above.


10. Does the operator need to be highly educated and experienced to operate the Pope still?

Not necessarily, but this is not a “set it and forget it” operation such as in the case of a rotary evaporator or other simple batch device. Being that this is normally the final processing step prior to packaging, that the feed material can have varying composition and quality, that the final product specification goals of various batches may vary depending on management, marketing and retailer preferences, and that the Pope still operation can be adjusted to accommodate these variations, there is some thought that goes into proper operation. With good analytical information on the distillation feed material, well laid out product goals, and an operator who is interested and strives to learn and to accomplish these goals, there will be much greater success than where some of these factors are missing.


11. Does this equipment work well for distillation after different types of extraction methods and other processing steps?

Yes. Whether the extraction method used is butane/propane, supercritical CO2, ethanol or other means, distillation with the Pope stills will perform excellently and will significantly increase product purity. And whether or not the material has been winterized, (dewaxed), or whether or not it has been decarboxylated, the distillation will likewise provide excellent results. Of course the final product purity, yield and appearance is also affected by initial plant strain and quality, the type and quality of the extraction process and the subsequent steps carried out prior to distillation. There are some rule of thumbs as well, for example, material that has been winterized will result in distilled product that is more optically clear and of greater purity than non-winterized material.


12. Why wipers instead of rollers?

Pope’s diagonally slotted wipers are designed to provide optimized thin film turbulence and to not only propel the material in a circular path around the inner cylindrical heater surface, but also downwards, resulting in shorter and controllable residence time. Rollers utilized by other manufacturers rely on gravity for the downward motion, are not as efficient and may also fling residue material to the internal condenser.


13. How is training and installation handled?

There is no additional charge for this; it is free to our customers! Personal training and demonstration (with non-cannabinoid materials*) is performed at our Saukville, WI facility, 25 miles north of Milwaukee. Clients visit sometime between the time when equipment is ordered and when shipped. This is done privately, one company at a time – you receive full attention, without the presence of any potential competitors. Nearly all users have found that after this training and demonstration, they are able to set up and start operating the equipment themselves, making good quality product the same or next day after receiving the still, with no difficulty. Of course we are always here for questions via phone or email, again without charge. Special trips to client’s facilities can be quoted if necessary.

*While Pope sells equipment to licensed cannabis companies in legal states, we are located in Wisconsin which is not currently a cannabis legal state. Accordingly, Pope can not and does not handle or process any cannabinoids at our facility.


14. What other equipment does Pope offer?

Our wiped film molecular stills (WFMS) are one of the versions of the family of Pope’s wiped film stills (WFS). Another version is the wiped film evaporator, (WFE), which is similar to a WFMS except that there is only an external condenser and no internal condenser. These operate at weaker vacuum levels and are primarily used for removing large percentages of solvent from less volatile components. This can include, for example, bulk removal of ethanol from heavier materials such as cannabinoid after extraction or winterization. In fact, Pope’s WFE’s are utilized in the cannabinoid field for this purpose, particularly when the quantity of solution to be concentrated becomes greater than what is practical via rotary evaporators. Pope also offers a wide range of custom stainless steel portable pressure vessels, tanks, reactors, mixers, dispensers and fully customized turnkey processing systems. In addition, Pope’s pressurizable nutsche filter-dryers are available in many sizes and configurations. These vessels and nutsches are utilized in many industries, including cannabis.


15. What is the history of Pope Scientific, Inc. and the Pope Wiped Film Stills?

Incorporated in 1963, Pope has been serving companies and institutes worldwide with technology and processing equipment for labs, pilot plants and production. The WFS product line was developed by The Arthur Smith Company in the 1950’s and transferred to Pope in 1975. The WFS’s have been used in a multitude of heat sensitive product applications, including pharmaceuticals, vitamins, cosmetics, nutraceuticals, foods, flavors, fragrances, edible and essential oils, extracts, polymers, bio-based materials and fuels, waxes, specialty chemicals., etc. In addition to providing equipment, Pope has a very active toll distillation processing, lab and pilot services department – we know about processing! Pope is, “Solution Driven”.