On a second round of freeze precip. that my friends cat did from the Noman Tek the final product is yellow powder. She did three pulls of naptha on the first round and ended up with pure white powder after the freeze. She reused the naptha from the first round and combined it with the naptha from the fourth pull (which sat a few days in the jar) and this time the result is yellow powder.

Is this fats from the MHRB? Is this some kind of dangerous residue from the lye? Will recrystallization get rid of it?

Most likely oils from your fourth pull, it’s unlikely that it’s dangerous contamination of your spice.

I think its a good idea to keep your pulls separate, they seem to get much oilier over time. The oils can easily be removed with a re-x or two.

Yeah especialy with reusing unwashed solvents the oils seem to accumilate.

My friends cat did a recrystallization and it's nice and white now.