So... after all these years, I'd like to update, since I have gone to bulk processing since the original tutorial on canncom.
One pound plant material (I use higher end brick shake since I'm lucky enough to get my buttery mitts on it) per 8 pounds butter. I throw in 9 pounds for good luck, and I'll explain why later.
Get out your biggest iron skillet and a pasta pot that can rest in it so there's good contact between them. This is to spread the heat. Put your butter, plant material, and an equal volume of water in there. Set stove to very very low. Put on some nice music and go give it a stir every so often; I recommend starting on a Sunday morning and treating it like chili. Give it several hours to extract, then strain into a half gallon mason jar which you MUST put UPSIDE DOWN in the fridge.
Return the plant material to the pot, add another pound of butter and more water, and repeat.
Do this once more.
After 3 extractions, you should have a bunch of fully spent plant waste, and several jars in the fridge. The jars (Which you put in upside down, right?) Will have water on top when opened. Pour it off. This water is all the garbage you wanted to remove.
Gently re-melt the green butter in warm water, being careful not to thermal shock the glass. When the butter is liquid and the jars are warm, add hot water and shake vigorously.
Cap them and put them in the fridge upside down again.
Repeat until the water runs clear.
Same deal, bigger volumes.
I use a 2L separatory funnel for the final water removal these days but the upside down mason jar method is still the standard for most applications.
I'll post my caramels recipe with pics next time I run a batch