Jump117 shared an extraction technique with us on IC Mag forum, that used a stainless thermos to keep the LPG liquid longer, so as to increase residence time.  To conduct our experiment, I first made a trip to Goodwill, where I picked up a couple stainless thermoses for about $8.00 each.

My first step was to wash and sterilize the thermos, toss the screw cap, and to drill three holes in the cup covering the screw cap.  I drilled one 1/8” hole in the center, and two 3/16” holes either side of center to allow fumes to vent.

Drilled cap

My next step was to accumulate the rest of my material and equipment, which besides the thermos included a can of lighter butane, a bain marie set, a strainer, and material to extract.  Not shown is a cooler full of ice to store the butane in outdoors.


Next step was to load the material to be extracted into the thermos, which we packed lightly and filled about ¾’s full.

I then placed the thermos in the freezer at -18C/0F and the butane into a cooler full of ice to chill overnight. 

I didn’t put the butane in the freezer, because the valve seals lose resiliency as the temperature drops, and they are more prone to leaks, leading to possible explosions.

Chilled thermos and butane

After selecting an ignition source free outdoor space with adequate airflow, the next step is to inject the chilled butane into the thermos through the center hole in the cap.

Injecting the butane

Once the thermos is full of butane, it is covered to insulate it and placed in a well ventilated shady spot to soak. 


After a 10 minute soak, we rapidly drained the thermos by removing the cap and dumping the thermos inverted into the strainer, which we had sitting over the bain marie.


We then allowed the butane to boil away, aided by tap hot water in the lower bain marie container.

Boiling off.

Yield from low grade trim before winterizing

Our last step was to add 190 proof ethanol to the bain marie and dissolve the extract at a ratio of about 10:1.  That solution is then poured into a canning jar, sealed and placed in a -18C/0F freezer for about 48 hours to precipitate the waxes, at which time it is filtered.  See 10.2 Winterizing.

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