I have some old bubble about 3-5 years old, which I want to turn into a tincture, Is decarbing even necessary at that age ?
Would I wind up converting THC/THC-a into CBN, This would may even be beneficial for my purposes as im a true light weight ?
Four different conversions are contained in your question.
THC-a ----> THC (decarboxylation)
THC -------> CBN (oxidation)
CBD-a -----> CBD (decarboxylation)
CBD --------> ? (oxidation)
Also, terpenes can convert, oxidize and evaporate during heat-driven decarboxylation of your bubble.
All of these reactions take place at different rates. So, what you are asking is really complicated. From what I've read, decarb of THC-a is the fastest of the four reactions listed above. As
@chemphlegm says, the THC-a has probably already completely converted. That said, CBD-a rate of decarb is significantly slower than THC-a decarb rate. CBD-a may not have entirely converted to CBD after 3 years. I haven't seen any studies on this so it's just a guess on my part. This is all a guess without chem analysis.
It sounds like you are interested in the terpenes and/or CBD. If you are interested in terpenes, then don't heat the herb. If you are interested in CBD, then to be sure it's all converted, I'd decarb. If you are interested in THC, then you I would not decarb.
I've been experimenting with lower temperature decarb using a water bath to control temperature with good results. The purpose is to reduce oxidation, keep more terpenes and avoid stinking up the house. . From my experience, you could probably decarb your bubble by placing
your loosely stoppered vial into a zip lock bag and immersing the bag in simmering, not boiling water for 2 hours. Assuming decarboxylation is still possible in your stuff, you'll need to weight the bag to keep it from floating. Another option (that I haven't tried) would be to place the loosely stoppered vial in an otherwise empty mason jar, seal the mason jar and immerse it in simmering water. You'll need to weigh the jar down too.
Please note that decarboxylation generates carbon dioxide, which if confined in a fixed small space will develop pressure. If you heat the "bubble" in a sealed glass vial, the container can break under pressure. This is why I emphasize "loosely stoppered". A mason jar is designed to leak off excess pressure through the sealed lid and so, won't develop pressure either from gas expansion or CO2 generation.
I'm haven't invested in chemical analysis. I test with my head. Not very scientific, but my head knows how high I get. Just saying that I'm speaking from personal experience and not hard data.
https://www.rollitup.org/t/sous-vide-for-decarboxylation.906933/