My boyfriend used my All Clad skillet to fry corn tortillas in grapeseed oil. Now I have brownish grease spatter marks all over the sides of the pan that won't come off. I have tried Bar Keeper's Friend, Magic Eraser and general elbow grease with SOS. They are a little lighter but still not clean. Does anyone have any tips on how to remove them and also (other than not using that pan) how to avoid burned on grease spatters stains in the future?