Hey Hugo. its a bit of a process but here goes.
First I put weed in freezer in large ziplock bag for 24hrs. I use either scrap/scrappy bud or trimmings. When its good and frozen I crush it up in the ziplock bag so its ready to soak in ISO. I ususlly do 150 to 250g at a time.
Next leave crushed weed and ISO in the freezer at -23c for atleast 24hrs. Pour enough ISO to cover weed by about an 1 to 2 inches. shake the hell out of it for about 1 minute. Back in freezer. I shake the hell out of it for a minute 5 or 6 times over an hour long soak. Then coarse filter into a 4ltr glass jar. I leave it sit for a few days in the jar and all the solids settle. Its usually got some chlorophyll in it. I syphon off into another jar and leave solids behind.
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Then get rid of the chlorophyll and color correct with about 1g per liter of powderized activated charcoal. This should only be in the mix for around 10 minutes. shake vigorously every couple of minutes. Then I vacuum filter thru a diatomaceous earth cake filter. It catches all the activated charcoal and any particles down to about 45 microns.
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Then vacuum filter thru a 0.22 micron filter to catch any mold spores etc that may have made it thru the previous filter.
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I have a double boiler setup with an electric wok with a light cooking oil in it and a large stainless mixing bowl for evaporating off. I set the temp very low like around 120f. it usually takes between 8 and 12hrs depending how much ISO was used to evaporate down to a descently thick oil.
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Into the vacuum chamber it goes. I vac at 100f for probably 10 mins or so, release vac, and stir/whip the concentrate, put back under vac, repeat probably 6, 7, 8 times. the ISO is usually completely gone in a couple of hours.
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I whip the heck out of it and put it in a jar, its usually curing as I'm doing this, crazy. next morning it looks like this.
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Sounds like a lot of work, and it is but I really don't mind. I've been growing for 40yrs and have made a shit ton of the old green oil. It was not bad stuff but doing it like this is just pretty cool and its pretty potent to boot.