When at home I often smoke joints from my gravlab nano.
I get some great rips on it and no ash or debri in the bong.
I only smoke hash with it or joints. So, while there is no ash, it does get resinous pretty quickly.
So I use a bit of everclear every other day to try and stay ahead of the buildup.
I have been pouring the "dirty ec" into a jar kept in the freezer.
stuff looked black and nasty and smelled .. like funky bong.
So I decided to see how clean I could get it with my usual methods.
"Froze", filtered, re"froze", filtered
Still very black and suspicious looking, but not nearly as nasty smelling
"froze" solution in jar again
prepared iso/dry ice bath
placed freezing jar with ethanol/resin solution into iso/dry ice bath for 5 minutes,
carefully filter remaining ethnaol/resin solution into silicon bowl
place in oven at 115f until ethanol has evaporated
then for apprx 12 hours total at same temp (can be in batches of 2 or 3 hours but needs at least 12 hours
what I had left was a very black shatter with just a hint of the resin smell and taste.
stuff hits you square between the temples.
I might put it through one more bath to see if I can get the rest of the "burnt" out as it isn't something I would smoke if I had good herb around, but if you run feast to famine like a lot of hobby growers do, this might help you through the famine.