Hi,
unfortunately it is not possible to source mhrb in the country of a friend so he has to rely on vendors.
Last time he did so he got pretty orange spice and as this seems to be the result of a poor extraction he was thinking of washing it.
From what he read it has to be solved in solvent which does not solve the impurities which should sink to the bottom of the glas the solvent is in, then the solvent gets carefully poured in a glas dish which is put in the freezer as the solvent wont freeze and stay liquid but the solved ingredient will crystallize and so the solvent and the crystals can be seperated leaving hopefully better crystals.
Hope my friend got that right.
Now he read that he could use naphta or heptane as solvent and is wondering whether the solvent will at least partly evaporate within his freezer and if there is a solvent which is superior.
IF my friend got this wrong he really would appreciate some help and if the general idea is right it would be awesome if he got some hints on the solvent (could he put a lid on the glas to prevent any evaporation?)

Thanks for helping

You can tightly wrap the crystallization dish in foil or cover with a lid if possible. For purification, a mini A/B cycle might be better and more effective. You can simple dissolve your DMT freebase in some vinegar, add a base such as sodium hydroxide or sodium carbonate, the solution will turn milky white. Add a small amount of heptane and shake, separate the layers, pull the heptane layer and add it to the crystallization dish. Do 3-4 pulls in total in the same way.

Simple recrystallization doesn't work very well, warm heptane ends up dissolving the impurities again. An A/B cycle works much better. You also don't need to warm the heptane.