Attempting second pass THC short path

Attempting to do my second pass. Mantle temp is already up to 225c and head temp is lingering around 33c. Vacuum is 29.8 in Hg. Any ideas why head temp staying so low? This vacuum worked for first pass at this pressure level, does the second pass require more vacuum pull or higher temps?

You need to get a better vacuum gauge, short path without a micron gauge is always going to be a crapshoot.

Bullseye gauge is best but you can get a cheaper supco gauge on amazon.


Thanks for the info. Could my problem be the boiling flask being too small for the surface area of the heating mantle.

Use fireplace rope to fill in that huge gap or buy the proper size mantle.

Better vac pump for sure is needed. Sounds like your running a hvac vac pump and not one many for spd use.

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I had the rope wrapped around it but took it off to take a pic. What vaccuum should i be aiming for?

You really want to be getting at least 300 microns, ideally better on second pass.


Alcatel 2021i
Leybold trivac 2.5e


Second pass usual needs less heat to distill then your first pass, its a purer product with less gunk in it. If it worked for first pass, u gotta have a leak somewhere.
When u say mantle temp, is that a thermometer in between the mantle and the boiling flask or of the liquid temp in the bf? 230C is quite high for the liquid temp.
I see ur using a thermometer adapter, those are prone to leaks, check that. thermowells work much better for future runs. Also check between ur pump and the glass, any lines or valves lesking?

Regardless the color on that first pass was pretty good :ok_hand: was the crude from bho?


You got a really small flask, this pump should be more than sufficient:


Thanks, first pass was crude.

Crude is the starting material, normally. 1st pass is normally distillate. Then 2nd pass 9n the 1st pass distillate.

Yeah i meant starting material for first pass was crude.

Correct terminology goes a very long way here. This way we dont steer you down the wrong path.

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