35% peroxide is pharmiscutical grade. You can't use it straight when bleaching bones or skull you need to delute it down. It will deslove or breakdown delicate bones. Depending on the thickness of the bones. I delute mine down to about 15% for buffelo skulls and let them sit in it for about 3 days then let them dry for a couple of weeks. If they need a second bleaching I do one. As for the peroxide you get at the store, it is usually 3-5%