Take your raw, unpurged oil and mix it w/ about a tablespoon of isopropyl alcohol 91% (Safeway DOES stock 99%) per gram or so of raw oil. This isn't winterization, you aren't dewaxing, though you could integrate that process easily at this point. This just forms a solution with a far far lower viscosity than a big ol' glob of bubbly, raw unpurged oil.
In this low viscosity liquid state, the butane can easily and rapidly escape the solution.
Terpenes can too, so be wary of temperature. I use a plate on a pot of very warm (NOT BOILING) water. The alcohol/butane will purge quickly. Keep good ventilation and avoid open flames, of course, but iso fumes aren't particularly dangerous, and most of the butane has already evaporated by the time you have raw unpurged oil.
Using more alcohol will take longer to evaporate and you'll lose more
terpenes. Remember we're just trying to thin the oil enough so that the bubbles can escape easily. You may be able to get away with less than a tablespoon/gram. Be patient with heat and temps, iso evaporates VERY quickly. Acetone could easily be substituted for iso, and will evaporate even quicker. Smells far stronger and is more volatile.
