yes you can evaporate, but youll be left with a less pure product, probably. Be sure to wash your solvent to remove potential lye/polar impurities. If its very impure, recrystallize (instructions are in the FAQ). I also recommend after you think its all dry and done, redissolve in non-denatured alcohol or acetone and re-evaporate to help removing traces of naphtha (your crystals wont look so nice as when you recrystallize and evap slowly, but its better for your health)