benzyme's epsom salt technique seems useful (though I've never tried it). Magnesium Sulfate Heptahydrate is cheap, easy to find, and would probably do the trick with minimal loss of goods. I don't know what kinds of minerals or chems might be introduced into the NPS this way... but benzyme tends to know his chemistry.
That said, I see absolutely no reason to bother with cleaning spice at all.
First off, minor amounts of lye are not a problem... even if they could actually make it into the final product. 1) Lye vapes at ridiculously high temps... nowhere near the DMT vape temps 2) People ingest lye all the time. Pretzels are made with lye. As are dozens of other baked goods.
This might be controversial, but generally the stuff that gets removed with washing is good stuff. Mimosa oils and mysterious potential jungle alks are not contaminants. When you toke your first toke of some sweet honey spice, you will wonder why you would ever want to remove those oils. Sure, some clear pointy crystals are nice to vape, and the clinical, sci-fi clarity they give is worth experiencing... but the honey and jungle are where the
love is. If you are not using harmalas or making changa with harmalas, you might be stoked to leave those oils in there. Even if you are fully harmala'd out, those oils are
rather nice. (subjectively speaking)
At any rate, if you evap your solvent slowly (and are using a solvent that selects for DMT well) you will get white or even clear pointy crystals without any extra steps or loss. Naptha that contains toulene will pull some jungle with it, but mineral lamp oil (parrafin extra pure lamp oil) as well as many non-zippo napthas will produce clean crystals with no effort. Another benefit to the lamp oil is that it doesn't stink up the place, is far less toxic than naptha (actually ingestible to some degree), and it is cheap. Here is the
thread where I found out that it works. It evaps slow as hell, but that just ensures that you have nice spiky crystals waiting for you when it is done.