Per the manufacturer's label:

"MS 70 does not change the color of your coin but does remove surface contamination and tarnish. MS 70 will allow the natural beauty of the original surface to show as brigt as the day your coin left the mint. MS 70 was deisgned to be used on mint state or proof coins, but does wonders on AU or slightly used coins. MS 70 restores the brilliant surfaces that remain under the tarnish and contaminants that has acccumulated on your coin."