what HG" of vacuum is optimum for purging solvents from say spice alkaloids, or mesc alks

For Bho they use a 29" hg vacuum and some slight heating to fully purge.

and i was wondering if one was to build a similar setup and use the same vacuum would it be

suitable or could it damage the alks?

29" is fine.

vacuum w/heat doesn't damage alkaloids (although with enough heat, some will sublimate)
but at 29", you won't need any heat.

thanks for the info.

any idea how long vacuum should be held for? (guess it depends on amount being filtered)

and what signs to look for once the alkaloids are fully clean

depends on the solvent being used. low-boiling solvents like light naphtha don't require much vac, perhaps a couple minutes after you see the solvent completely sucked through the filter. what you should see is clear crystals left over. btw, the solvent being filtered should be cold ( freeze precip'd), not heated.

if you have a vac that can pull 29", i suggest also purchasing a vac desiccator. this will dry anything you need it to, esp. mushrooms

yes, i was thinking acetone, which is pretty low boiling, so im guessing it wouldnt need very long.

would a vac dessicator be more like a vac chamber? so you can just place mushrooms or even filter paper with alkaloids in the bottom of a heavy duty stainless steel pot with a lexane lid and run the 29" vac and strip the excess solvents that way. or dry said mushrooms quickly!