Regarding the distillation of Cannabis oils in a lab setting, a workflow involving multiple cuts to remove several fractions of terpenes from decarboxylated crude oil ensures the absolute deepest vacuum possible during the cannabinoid pass. These terpenes must be removed as their highly volatile nature creates vapor pressure, which in turn increases the volume of gas that must be displaced by the pump to achieve a desirable distillation pressure for the desired oils.
After this step, preliminary fractions often referred to as the, “tails” will be distilled. This fraction is usually of lower quality and is separated from the main fraction known as the, “heart” fraction of the distillation which will yield the more pristinely colored and pure distillate. The end portions of the distillation will also present with subpar quality oil that is separated and is also referred to as, “tails” fractions.
The resulting lower-quality products are often used as the base for edible or topical products as opposed to the highest quality distillates that will be found in vape pens.
As the industry evolved, however, there stood another piece of technology that would be applied to cannabis distillation just as the short path distillation array had before it. Wiped film distillation has been used for many years in the refinement of petroleum oils. With a small shift in parameters, it was clear that an automated molecular distillation solution was the destiny of cannabis purification. Wiped films went on to become the standard for production scale distillate production for a myriad of reasons. With jackets through which heat regulated transfer fluid is pumped to heat the inner surfaces of the distillation array, a more sophisticated molecular distillation machine was engineered.
Wiped film distillation units use wipers to apply a thin film of oil onto the inside of a heated cylindrical surface from which the desired cannabinoids will evaporate in real time as the crude falls down the column. At the center of the wipers is situated a condensing coil that is chilled to condense the distillate as would be done on a short path coil.
This methodology ensures the absolute minimum residence time for the sensitive cannabinoids on the heated surface. At the base of the evaporator cage, the evaporative and condensing surface areas are separated and reduced to two arms from which the end products are dispensed.
With the use of gear motors for the delivery of the oil onto the column from the heat jacketed holding tank as well as the dispensing arms, the need to break vacuum to change vessels is eliminated. This feature is particularly noteworthy as the oxygen from the atmosphere in contact with the sensitive and hot cannabinoids will allow the oil to burn on itself and show as a dark striation in the finished product.
Also numbering among the improvements to a traditional short path distillation is the incorporation of a more robust turbo molecular pump that can be used to achieve vacuum in excess of 1*10^-4mbar. The combination of the low pressures as well as the maximized surface area make for a yield that is considerably greater than conventional distillation arrays.
These units can even be plumbed together using a heat jacketed transfer hose and set to distil terpenes one array through to cannabinoids on the second column. Any operator would see the operation of a wiped film distillation array as a massive improvement when being able to move away from the need to rely on the replacement of flasks or a batch system for manufacturing scale production of distillate. Cleaning the surfaces of each piece of glass used during short path distillation is a chore that is all but eliminated by a sophisticated wiped film distillation array.