40 volume peroxide from a hair salon place works well. We could go on and on about how to clean skulls but its all on here somewhere. Youll have a hard time getting a boiled skull completely paper-white, but unless youre a perfectionist, its no big deal. Id rather have a little grey or yellowish color than a spray-painted skull.... I still boil almost evrything I kill, but mostly cause I dont have anywhere to put the stinky beetles in the off-season!