I know these types of extracts aren't very popular, but then again I've never seen any proof of success.
Thought SWIM should share his experience for the nay-sayers among us...
Starting material: Anything bound for the ashtray (minus beans), including resin, partially smoked bowls, stems, etc... basically a black tarry mass approx. 10 grams.
Procedure: Starting material dissolved in 91% isopropyl and solids were filtered out via cotton balls in the neck of a funnel. This is where roughly 3/4ths of the mass was separated from the actives in solution.
Next, the iso was completely evaporated via dehydrator. Naptha was added to the residue and heated till the residue dissolved. Naptha/actives were added to a mason jar along with an equal part of water. Mixture was shaken and allowed to separate, then water layer was discarded. Previous step was repeated 3x with warm water. Final wash used 1tsp sodium bicarbonate in addition to the warm water. Naptha was then left to dry with the aid of the dehydrator and the product can be seen above. Nice red/amber honey resulted.
It tasted somewhat neutral upon smoking, but was very potent. Yield was 1.8g which was added to organic coconut oil and encapsulated for later consumption.
Call it recycling...
Further improvements: add an extract of some nice herb for flavor if u intend to smoke it.