Use a smaller amount of NPS and do multiple freeze extractions. Let them dry thoroughly.

Finally, if you want a really fantastic show off product, take your crude product, it will be somewhere between a white orange goo and sea salt in consistency. Add the crude product with good stirring a known volume of the lamp oil over constant heat. It should be hot but not so hot as to be fuming. You are attempting to reach the saturation point of the NPS, which you will know when the DMT stops dissolving. Add a little more NPS and allow the rest of your DMT to dissolve. Add finely separated activated charcoal, and continue stirring for 10 minutes. Filter off the charcoal through a hot funnel into a hot beaker. allow this solution to cool to room temperature, then place in the refrigerator, after this solution is cooled in the fridge, finish preciptating the last of the crystals in the freezer or in a dry ice bath.

This should yield large crystals with a sharp melting point and little impurity or discoloration.