Freeks recipe, no heating or bulky storage requirement:
Stock 7.5% PTU in 100% DMSO (0.75g per 10ml), store at 4C
use 40 ul per 100ml embryo medium to get 0.003%
I use +/- 9ul per petridish, swirl immediately after adding.
Wear gloves!!, DMSO helps PTU penetrate your skin