i had only been doing leather work a few yrs.not long at all.but my two cents are,i take leather on the flesh side run warm water until its good and wet.stick in the fridge over nite in a plastic bag.and the next day when im gonna tool.let it return it to color and go ahead and tool.i was taught the warm water would pentatrate good.dont know if it does any better than cold water.works for me,happy usually way it comes out.