Head Vapor Temperatures:
- Volatiles /Terps 65-100C (80-140C mantle temp)
- Head Fraction 101 – 155C (140 – 185 mantle temp)
- Main Body 158 – 180C (195-205 mantle temp)
Light Volatiles / Residual Solvents
Usually we will start our deep-vacuum distillation with the boiling flask contents at an approximate temp of 65-100C. This is the typical temperature at which you can easily transfer the crude material from one vessel to another at a reasonably low rate of transfer loss. At this temperature, you can assume that there may still be a small concentration of solvent and volatiles. If you are coming from a winterization / rotovap pre-process, alcohol/water azeotropes will be the most prevalent fractions coming out at this temperature as well as some light terpenes. If you have not previously activated or decarboxylated your crude – you will have a fair bit of activity in the flask as the Acid groups (the A in THCa) start to detach from the THC molecule and leave the system as carbon dioxide. It’s important to have your head and subsequent condensers set to the coldest possible temp during this process to avoid soaking your pump and cold trap with volatiles (which will affect your vacuum performance later if done improperly). We recommend a pre-distillation “punch-out” on a hot plate or in your Rotovap prior to transferring your crude to the SPD for initial distillation. This will preemptively safeguard you from having to deal with these vapors in your short path system. There are multiple methods to do this punch-out (sometimes called a degas/devol/decarb), you can learn about that in the next article.
Stirbar speeds should be ramped up to ¾ of the bar’s maximum potential as quickly as possible without knocking the bar out of position. (More on stir-bars here)
Step up by 10 degrees on the mantle as your ramp up your boiling flask temperature at this stage.
Once you have transitioned beyond this step, you will notice a clear fraction of terpenes and other aromatics condensing in the head. Your boiling flask temperature will be around 100-140C with vapor temperatures spiking upwards of 110C. You should keep a low temperature on the condensers and keep an eye out on your vacuum depth.
Chlorophyll, Esters, and heavy Terpenes
Boiling flask 140-175C will yield some interesting fractions – these will vary depending on the type of crude you are working with and the temperature of the solvent during primary extraction (IE BHO vs. Etoh vs. Co2). Typically, we will start warming up the condenser temps gradually to avoid a clog in the pathway – these compounds are not as volatile and require a bit more heat to slide out of the head. 35C is a good number to set your chilling/heating unit to this stage. You will notice a menagerie of colors including reds, yellows, and eventually greens. Azulene blue may also show-up at the peak of this temp range if your vacuum levels are deep enough.
Once you achieve 175C on the mantle and you still have not “popped” your cannabinoid fraction, continue to ramp up you mantle 3-5 degrees until you do so.
175-190C is where the fractions that will look most like distillate start coming out and it’s important to let them deplete and work temps up slowly while monitoring the vacuum levels carefully. These fractions have a distinct odor, which a lot of people complain about – It’s due to rushing the distillation during this step. The key takeaway here is if your head vapor temperature probe isn’t reading ATLEAST 158C, you are NOT pulling anything worth collecting. Not Yet. Condenser temperature should be ramped up here to 65C (if your system has vacuum lines), or 85C (if you have a hard-pipe system without GL connections).
At these temperatures, remember that cannabinoids distill out of the flask as a liquid, not a gas – If you see a golden liquid coming out of the condenser discharge but there is little to no activity in the head (especially the vigeroux), it is not the fraction you seek! Keep a close eye on your head vapor temperature as well as your in-system vacuum depth.
Fast Pass Procedure
Now that you have “popped” your THC or cannabinoid fraction – you can ramp your mantle temps slowly upto 200-220C. There are many mantles with different heating elements and rates of heat retention/distribution – regardless of the advice being offered here – I personally would not ramp the mantle past a point at which the vapor temperature exceeds 200C – this will largely depend on your vacuum levels in the system. The purpose for this steep increase is to accelerate the rate of distillation and get everything of value out of the boiling flask as fast as possible as cleanly as possible – feel free to tweak your individual preferences for this as needed. I generally do the bulk of my fraction refining during second pass where stir bar RPM speeds will play a larger role in the overall success.