Vacuum Level Fluctuations

I recently upgraded to a bullseye gauge and I get alot of vacuum fluctuations throughout my runs. I’m using a full bore setup with the bullseye probe between the VTA and cold trap. The vac level remains pretty stable until I change the temp or spin speed. I’m confident I dont have any leaks. I’m just trying to understand what’s going on…tia

  1. Is your Crude fully decarbed?
  2. Have you fully recovered all solvents from your crude?
  3. Have you already performed a terp strip/devolatizing step on your crude?

what he said ^^

sounds like there is something left in your oil, that’s why it only fluctuates when it is agitated or more heat is added.

Yes to 1 and 2. I typically strip terps in the boiling flask.

Turns out, when boiling something from your flask, and it wanders past your heatdprobe heating it up, you’re also gonna see changes in the vacuum level…

The real question is why have you never noticed the fluctuations before?


I just got the bullseye. This is my second run with it. I noticed the fluctuations both times. I figured it was vapor passing by it, I was trying to understand what it was and if it was normal is all.

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It is absolutely normal, and essentially why you have the gauge…

So you can see that shit go by…and tell when it’s gone (and it’s time to ramp).


Appreciate that info. I know I’ve been flying blind without it but I’ve managed to make some decent disty. Clearly wasnt seeing any of that movement on the analog gauge.

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What @mcpikeig said is accurate and if you have the stripping covered, it’s because turning up the heat and spin is increasing the boiling of cannabinoids. Any off gassing (terps or cannabinoids) is going to change the vac rate. This is how you set your flow rate. Usually when you have a good flow rate around 100 microns is ideal


Spend a little time wrapping your head around where the 50 to 50,000 micron range is on that analog gauge.

50,000 microns is ~0.2in Hg, so your gauge just looks buried…

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Gotcha gotcha. Thank you

I get the principal and I’m amazed I got the results I did without the bullseye. My first test came in at 82%.

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