it seem like you’re currently doing your math based on raw yields. I’d advise you to look at absolute cannabinoid yields instead. because the potency of your extract varies as you deplete the cannabinoids (at least with rm temp solvent).
have you had your crude potency tested? 65% cannabinoids is pretty standard if you’re doing it nice and cold. possibly 70%. does your biomass come potency tested?
6% yield on a second pass seems pretty high. unless you were running trimmed flowers at ~20% or better. I’m also guessing that’s probably closer to 4% cannabinoids (60% potency at best, possibly 50-55%).
I’d also be suspicious of losses to the roto flask at 5g. unless you left extra solvent in there to get it out. in which case you again need potency to make sense of things.
what % raw yield did you get on the first pass?
Did you have a potency on the last 15-18lbs of material? it wouldn’t really mater, because you don’t have a weight, but assuming you did, and a potency and weight on your distillate, then you could know your percentage yield, as cannabinoids, not just “oil”. if you sent the crude off for testing, you’d know your efficiency to crude, and from crude to distillate. both are useful to monitor.
yep, extra solvent means extra solvent recovery. which is why folks choose to run the same solvent over multiple batches of material. there is a sweet spot. exactly how you chose to skin the cat, seems to make a difference on where that sweet spot is.
Taking anyone else’s word for exactly where the point of maximum return is, is not something I would do. Because chances are nobody is doing it exactly the same way you are…
as for the rinse, I’ve yet to look into it. it just struck me as a clue that should be highlighted. in case it was important. asking @Montanadabman is probably more relevant.
edit: this is why i’m constantly harping on about the importance of in-house analytics.