I grew a cannabis plant and I can assure you that it was very potent. I don’t smoke but I vaporised once in a while. I prefer oil that I buy. I decided to decarb in a jar with olive oil to make cannabis oil and and to decarb at the same time. I cover the bottom of a mason jar with 1/4 cup of cannabis and I covered it with olive oil + about 1/8 of a inch. (I don’t care to eat the cannabis, so there is no straining for me. At 15 PSI, the temperature is about 248 F or 120 C. I cook for 1 heure and it was really not potent at all. I mean really really not potent. The next day I put it back for 45 minutes and it was not better. I am wondering if I didn’t destroyed the THC or if it need some air to decarb. I read an old post here and I will try a small quantity in a one liter mason jar without the oil, maybe at a lower temperature too.
The lower pressure is 10 PSI for most of the PCooker (238 F - 114.5 C), but mine has a 8 PSI (233.7 F - 112 C. I can assure that the cannabis is very potent in a vaporisator with a bag and I am wondering why it failed. I scooped maybe 1\4 teaspoon for a poor result after I tried a drop, then two and eating some at the same time. If the air is the problem, without the oil, the air will still be pushed out of the mason jar. The olive oil will reach the proper temperature with the water around the jar. This is why I suspect the air could play a good part in decarb, what do you think?