When I try to SPD my decarbed hemp extract it starts to produce a gas and this ruins my vacuum. Each time I push the temp up it produces more gas. In the end everything smells burnt.
I steam distill my hemp for terpenes. Then I extract the dried material with isopropyl alcohol and distill this off. I then winterize by disolving in 95% ethanol, putting in domestic deep freezer and 48h later centrifuging the solids out. A further 24h freeze will cause minor tar deposits on the bottle walls, but no solids in the liquid. I then filter this liquid and distill the ethanol.
I have used various parameters for decarbing and have tried doing it either before winterization or after.
2h @ 135
5h @ 135
5h @ 150
5h @ 150 followed by 1h @ 160 and 1h @ 170.
I know these are excessive times and temps, but in none of these did the bubbles ever fully stop. They are slow at the end, but as soon as the temp goes up it starts again.
I use a 500ml magnetic stir bar mantle with rope on the flask. I initially thought my vacuum was the problem so I kept upgrading until my kit can hold well below 100micron through a distillation run (if it wasn’t for the gas).
A few things that might help with the diagnosis:
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If I just distill the run regardless of vacuum it will go to about 5000 micron with head temp up to 260c. If I then redistill this everything works as it is supposed to. It will stay below 100 micron and finish without burning. I have also distilled MCT with no problems (similar boiling point to cannabinoids). I would think this indicates there is nothing wrong with my kit.
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If I extract the herb with heptane the resulting winterized resin does not cause this gas evolution in SPD. This made me think the problem molecule might be a sugar? Heptane extraction is not an ongoing option for me though.
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If I water wash the isopropyl extract a couple of times the gas evolution is much reduced. I can get about 1/3rd of the run across clean before it starts gassing and burning. The ridiculous emulsions make water/saline washing difficult. I lost about 2/3rds in preparing a sample for this experiment.
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If I edge the temp up gradually over many hours I can maintain a vacuum of about 500 micron. But it took me 10h to distill 150ml of product and the upper end still burnt (I know this is a useless attempt. I was just trying to see if it ever stops gassing).
The burnt smell is overpowering, so not just a minor problem. It stinks out the whole room and the product is intensely bitter from it. Some of it can be steam distilled away, but the remainder still ruins the product.
I grow a high CBG strain that is not generally grown anywhere else except china. It is popular where I am but no one here does distillate so I have no idea if this is possibly a strain related issue.
Get some bromocresol green.
Decarb under vacuum.
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I did try the 2h @ 135 under vacuum.
Why does the vacuum help with this?
You are trying to boil off the volatiles yes?
How do you devolatilize before your WFE?
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Keep a light vacuum applied during the entire process. I would suggest using a smaller pump during the decarb (you will know CO2 is coming off because the oil will foam) to help pop the CO2 bubbles and a heavy duty roughing pump after 130C to boil off volatilizes. As always with vacuum have a cold trap and go slow. Decarbs can quickly get out of hand if your not experienced.
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The smell will always be there but you can contain it to a flask and not your entire room. Can you take a picture of the setup?
Some folks do overnight in their vac ovens…
Others 140C in an open boiling flask: How do these distillation numbers look to you? - #7 by Demontrich
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Not quite. There are no volatiles left after the stuff is held at that temperature for a while. New volatiles are formed with each increase in temperature. When I start SPD I can set it to 160c and it will gas for a couple of hours, then stop and vacuum will settle below 100 micron. If I then increase to 160c I need to wait an hour or more before it stops gassing at that temp and vacuum settles again. It gets the worst at around 180-190c where it will take several hours to stop gassing. This is also when it produces some water and some specks in the liquid that look like burnt protein. The water obviously gets pulled off fairly quickly, but the specks happen at the same time the burning smell starts.
The same process has been used for THC strains without this problem.
As for bromocresol green I presume this is to test for presence of the acid forms? Lab tests show there is no acid forms left.
Yes, bromocresol is to confirm decarb. Lab tests are expensive…and take days.
Or do you already have In House analytics ?
What do you have for a vac pump? (CFM?)
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Franz, how long would you recommend at 130c?
Just wondering because I’ve had it in the SPD vacuum set up for hours at 130, 140, 150, etc.
And yes, I use a small cheap pump for pulling the volatiles off before I switch over to the distillation pump.
Thanks for the bromocresol trick. I will definitely get this, but my point was that I already had these samples lab analysed. It’s been frustrating me for a couple of months now.
Edwards RV12. Like I said, I can do my second run at about 50 micron all the way through, so i don’t think it is my pump or kit that’s the problem
45% cannabinoids on the winterized extract.
Wow!! That seems extremely low. My guess would be that this is your primary issue. Feeding at 70+% cannabinoids is more traditional.
what is your input potency when you successfully use this protocol for THC crude?
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How do you get 70% in crude if the plants are only 5%? I know 70+% is standard for THC strains, but surely not for hemp. We are limited to 0.4% THC in our hemp and our strains are about 10:1 (with a bit of luck and heavy trimming maybe 15:1). So getting 4-5% in biomass is standard.
I can get 55% crude, before winterizing, from fan leaves. Which run less than 3% thc.
Your current winterization seems insufficient. -20 at 10:1 will not get the job done.
Colder. Less ethanol. Or try methanol.
What is the proof on your ethanol? Do you use a proofing gauge on your recovered solvent. If you’re not returning to 190 every time you won’t have good results.
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I just want to point again to the my comment #2 in original post. A heptane extract of the same material treated exactly the same in every other way did not cause the gassing problem. So I would have thought that it is not a decarb issue nor a kit issue. It’s something in the extract that does not get pulled out by heptane, but does get pulled out by isopropyl.
I have also tried to dissolve the isopropyl resin in heptane to see if anything does not dissolve, but that didn’t work as indeed a lot of stuff didn’t dissolve and just bound up the goodies.
How long are you soaking? What temp? Water content in iso?
For 70% unwinterized crude from 10% biomass, I extract for 5-8min at -50C. That was getting me 85% of the cannabinoids last time I checked.
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Can try methanol, thanks.
My ethanol is top food grade 96% (>190 proof). I have not reused any so as not to introduce variables. But I am also a distiller so accurate recovery won’t be an issue in the future 
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How about your primary extraction solvent and extraction parameters (as you believe it’s the extract that’s the issue)