Share 'Best Goo Formula?'

I'm a newbie and trying to find the best goo formula. I've tried 70% paraffin wax and 30% perc in salt water and get good lava flow.  After a couple hours white wax flaking starts and gets worse over time and accumulates at the top of bottle. The wax separation is very prevalent on top of cooled down goo.  I'm wondering  if my preparation of wax/perc is at fault? Maybe mixing too long/short, too…