This site has some of the best info on things like this, and just about any type of solvent extraction process you can think of. Good, scientific info, from science minded people looking to make top qaulity extracts, and to inform the average user on these processes.
http://skunkpharmresearch.com/glycerin-extraction/
Just so you guys know I do make non-spiked ejuice actually, and 99 time out of 100, DYI Spiked ejuices will not work like they say unless you using a RDA or another dripper, otherwise you are gonna be wasting at least! 30-40% of your material. I used to be a pharm tech and have exp compounding drugs in a legit lab environment before I started a e-juice co(2years ago). If you guy want a legit guide to get the most outta it, just let me know and I'll set some time out over the weekend.
making GOOD evape juice is not as easy as it sounds either. The problem is after a certain point, the cannabinoids will not stay in suspension. A special Homogenizer is needed, and a hand held blender won't even come close. More good info on all this on Skunkpharmresearch
http://skunkpharmresearch.com/game-changer-emulsifying-vegetable-glycerin-and-bho-for-e-juice/
SPR is a really informative site.
I refer to their site quite often for improvements on extract processes, especially their alcohol processes.
I seriously use it as a textbook reference site.
They have well written articles that I think provide very good step by step information as well as the reason one takes those steps.
They are very safety oriented and I don't see how any could go wrong following their material.
Mention "winterinzing" your hash to a lot of bubble hash makers and their eyes sort of roll back and usually I hear "dude, you are making it too complex".
Until I show them the exact method I got from that site, WOOH you will get good stuff if you follow their instructions and I will go out on a limb and say if you can't figure it out from their instructions, nothing will help you.
I plug them when it is appropriate.
I was just talking about this with a couple of friends on Monday and have just started looking into it myself. I'm curious to know what actually happens to the trics. When making oil and butter the THC is slow heated until it breaks down and binds to the fat in the oil. I'm assuming something similar has to happen to the trichomes for this to work in this application. At least to my understanding I can't see how it would work otherwise. After watching the video that Evol posted, thanks for that, I took at look at both propylene glycol and vegetable glycerine. PG is used as a solvent in pharmaceuticals. VG is basically vegetable oil. I'm wondering if the combination of the two, or maybe just the PG, dissolves the THC when it's slow heated like that. Guess I should have paid more attention in chemistry class.
There are some warnings on ingesting PG, especially for anyone prone to allergies, but it's generally considered safe for consumption. As such, that same process might have other uses in edibles as an alternative to oil or butter.