Hey, new user here. I decarb rosin as a hobby - I press flower rosin myself and my main goal is to get good flavor and visual appeal in the final product for carts.
I’ve been using the jar tek method (lid closed with the ability for pressure to escape) and while it gives me decent flavor, the color always comes out very dark brown. So I decided to try decarbing under vacuum, hoping to reduce oxidation and get a lighter result. My setup is a glass vial in a water bath on a hot plate stirrer with a temp probe, connected to a cold trap and vacuum pump. I started by pulling full vacuum (-0.1 MPa) on cold rosin to evacuate all oxygen, held that for about 10 minutes and started heating, then gradually dialed back to -0.06, then -0.02 as CO₂ started flowing. Eventually turned off the vacuum completely and let the CO₂ atmosphere maintain the oxygen-free environment. Decarbed at 80°C for about 5 hours, then bumped to 95°C for the last hour to finish it off. Bubbling stopped and the oil looked fully decarbed.
After decarb, I mixed in 5% mimosa CDTs and 5% True Terpenes Flow - which is more or less my usual recipe that has worked well in the past with jar tek decarbed rosin. The result was terrible. Basically flavorless, or worse, a burnt taste. Really disappointing. Very decent high though.
I’m wondering whether the vacuum stripped out something important during the decarb that the added terpenes couldn’t compensate for, or if I just had a bad batch of starting material (it was older rosin I was using to test the setup). Has anyone else experienced flavor issues when decarbing under vacuum? Would love to hear what might have gone wrong and whether it’s worth trying again with fresh rosin or if vacuum decarb just isn’t suited for cart production.
I am not a fan of doing anything to help viscosity other than a full decarb. I know it’s a personal batch but i’d put money on that being an issue. My god is it nice with someone being thorough with their details for once though. THANK YOU!
I can tell you 100% your issue rests with the fact that you’re using flower rosin. I did the same thing. Tried as much as I could to try to not have to fully wash hash and maybe find a workaround that was good for carts…no dice. Since you seem to be detail oriented I bet you put a bit of work into checking out which carts were good and which weren’t so I wouldn’t chalk it up to that. But since you actually put effort into this post and provided as many details as you can I’ll show you that I do in fact feel your pain and know where you’re coming from. I honestly think with your documentation this will not take you long to fix should you have the environment.
So, I should preface this with I totally was not aware of how carts should be decarbed nor did I have the tools to fill it properly at this point, but I did have a few things working on my side - brute force and a lack of shame. Flower rosin I knew was going to be a bust for carts because I could see just in the dabs I was taking there was so much black char happening that if that sort of thing caked up inside of a cart it wouldn’t last more than 30 seconds so I made a fair amount of sift hash…same.
I believe that was my starting material right there. Was a super nice smoke, regardless! But as soon as the decarb happened it got very dark even though it was refined and I got the large majority of plant material out of it on a really fresh batch.
I’m not going to tell you what to do since I don’t know your situation, but I think your issue is less terpene retation and more wax/fats being burnt and overshadowing any terps that might be in there. If you can either produce rosin with less waxes/fats by washing it or just making enough flower rosin that you can perform some sort of winterization you might be good. I would lean heavier toward washing it to get the flavor you want. Also keep very much in mind that is fresh frozen material that was washed which I totally get cuts down availability - I still strongly think washing would solve most of your problems. Keep it focused on the nicer micron bags (45-120 usually, maybe 45-90) and you will make fire.
Now just for comparison, here is one of my first few carts I made. Like I said. Decarb was not something I had comprehended at that point and I think members on here helped me smooth that out instead of laughing at me which is another reason why I feel like here on 4/20 I should pay it forward like they did.
Top one is the sift cart, bottom ones are the washed hash carts, super low and slow pressurized (but supervised and regularly depressurized before issues arise with plenty of headspace) in an oven at 160f for like 2-3 days or so. Repeatable and easy to dispense with extremely loud flavor without any needed additives
@SubstituteCreature Thanks for taking the time to answer, really appreciate the detail and the photos!
Pressing bubble hash rosin is certainly in my plans, and after reading your post I’m even more motivated to go that route. I’ll have to wait for my current grow to finish before I can give it a shot though.
A couple of follow-up questions:
Did I read correctly that you’re decarbing under pressure? That would be the opposite of my vacuum setup. Really curious about your process there.
Also, do you decarb until the bubbles stop completely, or do you pull it while there are still some tiny micro bubbles being produced? I’m wondering if I may have waited too long on that last batch and over-processed it.
One thing I observed during my last decarb was that there were no significant bubbles at 80°C, but it was still bubbling happily at 95°C. I’d assume it would bubble even more at 110°C, so I guess using bubble cessation as an endpoint isn’t 100% reliable — it seems to be temperature-dependent rather than a definitive indicator that the reaction is complete.
I’ve read through the threads here about vacuum and pressure decarbing and I understand the boiling point implications. My logic with the vacuum approach was to only pull full vacuum while the rosin was still cold, purely to evacuate oxygen from the system. As the temperature rose, I gradually dialed the vacuum back to avoid stripping terpenes. Once CO₂ started flowing, my assumption was that the headspace and hoses would be mostly filled with CO₂ rather than oxygen, so I no longer needed much vacuum to maintain an inert atmosphere.
Just wondering: if you decarb in a jar with a goal of having a pressurised environment, why not drill a hole in the cap and install a pressure relief valve similar to the ones they use in moka coffee makers? You would get more stable pressure and less babysitting throughout the process?
Is that a pressure rated glass jar? How much pressure are you aiming for?
Also wondering if you noticed a real world difference in quality between the pressurised decarb method vs the usual jar tech where the lid isn’t completely sealed?
Is it possible you’ve got some particulate in your decarbed rosin? Any piece of biomass is going to cause havoc on your cart’s coil. If you have more of the same batch, heat it up and filter it down to say 5 um and load it up.
I filled 3x CCell rosin bars, and all have the same burnt flavor (something I normally get when the cart is just about to finish). My current theory is that I just decarbed for too long. Not sure if the vacuum setup had any play in this process, but since using vacuum appears to be counter productive, I think I am going back to jar tech for my next attempt.
Am, so… If i want to make carts from rosin - i absolutely need to decarb? Flower rosin. Also - how to prevent loosing terps-flavor-smell while doing it?
Sealable container?? It might not open when cool-down. Also hard to find something like that idk.
Pressure decarb is fairly common nowadays, IMO. If you want to do it safely at home scale, it’s possible, but can go sideways quick, you’re basically creating a pipe bomb.
