iv done a few re-crystallizations so far, but just wanted to asked a couple more Q's before doing the final one.

im using naptha, what is the ideal temperature to heat the naptha to, (iv been doing about 140f) and how long should i keep it on the heat, do i remove
the yellow/orange oily stuff that forms at the bottom of the shot glass or leave it there? (iv been removing it)

iv been letting it cool to room temp and then putting it the freezer. but want to do a room temp evap this time. shall i cover the jar by 90% so it can slowly evap? or less/more? and what room temp is acceptable? its about 90f here

sorry for all the questions, iv done alot of reading and searching but could find the exact answers.

thankyou

Im not sure about the other stuff, but you are right in removing the gunk at the bottom..

yes cover it, cd works good, keep it in cool area in the dark.