I stole a snippet from skunkpharm...you should read through their pages, may help clear up any ?'s
Air movement over the pool speeds up evaporation, by whisking away the saturated boundary layer and providing the extra energy for the molecules of butane to escape the surface of the oil, as it is ricocheting about in the pool. Care must be exercised here, as any dust or lint in the air will end up in the oil, so usually a cheese cloth or similar porous cover is placed over it, before blowing over the top with a fan.
We can also speed it up with the application of heat. Any heat will speed up the evaporation, and one line of thought is to keep the heat low and around 60C/140F, using a hot pad after the hot water bath and scraping and popping any bubbles with a razor blade. A typical purge might take an hour and provides maximum terpene retention.
When adding bottom heat, you can also add aloose fitting lid, which will speed up the purging and keep out lint and dust.
For a faster purge,the temperature can be raised to above the melting point of the cannabis essential oils, or around 82C/180F, to give the butane molecules maximum mobility.
Instead of heat, vacuum may be applied to speed up the purge process. That is the process that we use when we wish to maintainthe cannabinoids in their carboxylic acid forms.
In thin film vacuum purging, we place about an 3/16″ of the oil in a 6″ Pyrex Petri dish, and place that in avacuum chamber, which also contains a hot plate. That allows us to manipulate both the temperature and atmospheric pressure, so that we can achieve boiling at very low, or even ambient temperatures.
While we use 180F to vacuum purge araw oleoresin, adding heat isn’t necessary when thin film vacuum purging raw oleoresins redissolved in ethanol. The alcohol will boil away under 28.5″Hg at ambient temperatures, as will the water that is left behind, even without adding any heat.
