There’s a decent amount of info on freeze drying but it seems to be inconsistent.
I know there are people on here who freeze dry flower to collect the terps (not sure if it’s frozen in those cases), implying the terps are boiling off. But I know people who make hash that use freeze dryers because they preserve terpenes better than anything else.
My hypothesis is that the cold temperatures cause the trichomes to be so stiff/viscous the terpenes can’t boil out (hash) and when people freeze dry flower, they aren’t actually freezing it.
I’m also curious if this can be used for some higher boiling solvents (let’s say ethanol or heptane) where it is 1:1 to 3:1 solvent:resin. If its concentrated enough it may actually freeze and then solvent can be boiled off.
I’m assuming this depends highly on the conditions you run but am confused by much of the information out there. Anyone have specific info they are willing to discuss.
The people using freeze dryers for hash are probably comparing that to using an oven. Those people are only trying to remove water, which, when frozen, can be sublimated off while the trichome heads stay intact. That’s what makes the freeze dryer “better” at preserving terpenes. The people using freeze dryers to collect terpenes from their flower aren’t doing that because it’s the best way to remove terpenes, but because it’s the best way to remove water. Once the water is removed, then the product will yield higher amounts because the water isn’t stealing some of the solvent’s capacity during extraction. The terpenes collected are just an added bonus.
I like your hypothesis. You might be onto something, but I don’t think it can be applied to solvents like ethanol or heptane because they dissolve the trichome heads. So, they wouldn’t be able to freeze and act as a barrier like you were thinking.
I see. I was thinking as a way to remove residual solvent like you would w/ a vac oven but instead you freeze the resin/solvent mixture then sublimate/boil solvent away.
The appeal of freeze drying is that the homogenous, then you freeze it and can boil solvent once the mixture is frozen, allowing for solvent removal via vacuum. Likely pulls lighter terpenes though
Yeah, I think it would be very difficult to purge solvent at those low temperatures. The reason pulling solvents in a freeze dryer would be more difficult than water (even though most solvents should boil off before water) is because the water never really mixes into a solution with the hash, it just carries the hash with it. Without the thc in the hash actually dissolving into the mixture and increasing it’s viscosity (and surface tension), the water can be easily removed. Once you have thc dissolved in a solution (homogeneous), it becomes much more difficult to remove the solvent. A vacuum oven at warm temperatures works better for that because you need to decrease the surface tension in order to purge the last bit of solvent out.
I know that this is an old thread, but I’m trying to understand terpene preservation and this forum seems like the most informed.
I’ve been running shatter for close to a decade. I started out open blasting into a dish and became obsessed with eliminating condensation until I eventually bought a close looped system. I used bone dry material because I was convinced that moisture prevented proper glassy shatter. It never dawned on me that terpenes were a liquidy, even though I’ve seen it in liquid form. So I guess I was also obsessed with removing the terpenes.
So now I’m wanting to update because I feel like a caveman with my old fashioned shatter. I’m trying to decide between making live resin or live rosin. I would need a lab freezer for the live resin or a freeze dryer for the live rosin. I would also need to buy a press for the rosin.
My question is, if terpenes are well preserved by freeze drying, why not use the material for BHO? Why is using a fresh frozen better? Wouldn’t the plant’s water content be the only real difference? Maybe the presence of lipids? If so, maybe deep freeze the already freeze dried material to locked up the fats while blasting? The only difference would be the lack of moisture, and in theory the end result would hopefully be shatter or something a little softer, but with a higher terpene percentage.
I saw the term “live shatter,” but there wasn’t much information and didn’t seem to be received well. I live in a rural part of the country and I’m out of the loop, so I don’t have much access to concentrates beyond what I make myself.
Great question! I’ve been learning about terpene preservation too lately, and this confused me a lot at first.
It’s not only about water content. Fresh-frozen material locks the trichomes and delicate terpenes instantly at harvest, so you keep the full original flavor for BHO/live resin.
Freeze drying removes moisture in a vacuum—this pulls out those light, easy-lost terpenes. That’s why freeze-dried material works amazing for live rosin (solventless pressing), but not ideal for classic live resin BHO.
Also explains why live shatter never got popular: you can’t have both the super clear glassy texture and full heavy terpene profile at the same time, they contradict each other.
If you’re upgrading:
Love pure solventless → go live rosin with freeze dryer + press
Want rich flavor & yield with extraction → stick with fresh frozen + closed-loop system
Freeze drying doesn’t really “pull out” terpenes the way heat drying would. It removes water by sublimation at low temps and vacuum, so a lot of terpenes are actually preserved pretty well compared to traditional drying. That’s why freeze-dried material can still smell very loud.
The bigger difference with fresh frozen is that everything is locked in immediately at harvest, before any handling, oxidation, or terpene redistribution can happen. Freeze drying still involves some processing time and exposure, so you can lose or shift some of the most volatile fractions.
For BHO specifically, fresh frozen tends to give a more “true to plant” live profile. Freeze-dried material can still be good, but it’s not quite the same as true live resin input.
So it’s less about freeze drying stripping terpenes, and more about fresh frozen preserving them in their original state from the start.
A good addition to this is the vapor pressure of the terpenes at the temperature is so low that they do not easily vaporize, leaving just the water that sublimates out.
At freeze drying temperatures (typically -40c to -80c) the vapor pressure of terpenes drops dramatically. Vapor pressure is temperature dependent — the colder something gets, the less tendency it has to escape into the gas phase.
Water at those temperatures still sublimates reasonably well under vacuum because ice has a meaningful vapor pressure even at very low temperatures — that’s the entire mechanism freeze drying exploits. You pull vacuum below the triple point of water and the ice converts directly to vapor and gets evacuated.
Terpenes however are larger, heavier molecules with much lower vapor pressures at those temperatures. They essentially don’t want to move. The energy just isn’t there for them to transition to the gas phase at -40c to -80c under typical freeze drying vacuum levels.
So you get selective sublimation — water leaves, terpenes stay locked in place. It’s not that freeze drying is gentle with terpenes by design, it’s that the physics of vapor pressure at cryogenic temperatures naturally protects them. The water is preferentially removed because its vapor pressure at those conditions is orders of magnitude higher than the terpenes.
That’s why freeze dried material still smells loud — the terpene fraction is essentially untouched because the conditions never favored their volatilization in the first place.
