Common Applications of Wiped Film Stills: Cannabis

Any series that discussed common applications of wiped film stills would be incomplete without mentioned their use in the cannabis industry. 

Wiped film still manufacturers experienced an extremely large increase in sales when the 2018 Farm bill reclassified hemp as an agricultural commodity. 

Today, the industry has shrunk some, with many cannabis companies out of business and profits dropping compared to the early days.  However, this industry is still an important part of any wiped film still companies customers.  In THC legal states, the stills are also used to purify marijuana.

Wiped film stills can be used as the final purification step to isolate the cannabinoids from all the other materials in the crude oil.  The stills are used after the oils is extracted from the bio-mass and it has been winterized to remove fats, waxes, chlorophylls, etc.

At this point the crude oil often contains four major groups of materials.  It can contain residual solvent (often ethanol), terpenes, cannabinoids and residual tar/waxes/dimers. 

Most of the time, the solvent content is less than 5% at this point, as the majority of the solvent removal is prior to the wiped film still. 

The terpenes are the flavor compounds from the hemp/marijuana plant and are responsible for that familiar marijuana smell.  The terpenes have a higher boiling point than the solvent, but lower than the cannabinoids. 

The residual tar/waxes/dimers are difficult or impossible to distill, but the cannabinoids must be distilled away from them in order to produce good colored product.

The actual process of producing pure cannabis is fairly simple. 

The crude oils is passed through the still at mild conditions to remove the solvent.  At this point, the oil becomes quite a bit thicker and is warmed up prior to pass two. 

For pass two, more aggressive conditions are applied, and the terpenes are collected as distillate. 

Finally, the crude oil is sent through the still a final time to collect the pure cannabinoids as distillate. 

Depending on the end product, the distillate could then go to crystallization or be used as is.