do best of both worlds. evap first down to an almost tar/goo. Sometimes it will evap all the way and u will have usable yellow crystals, sometimes not. But swim found if u dont evap swims freezer isn't cold enough to pull all of the spice out of a large cup of naptha. So although you will get whiter crystals, a lot of product will stay in solvent.
Then put that goo/crystals into a glass jar, add just enough nap to remelt it all, put the glass jar in another pot of hot water. once remelted, you should have a yellowish liquid. Then simply throw that into freezer.
It might still have a bit of a yellow tint, but in my eyes this is pure enough.