If using an acids such as Nick-A-Date, Lemon Juice or Vinegar & Salt, I would think that a Bronze Indian Heat Cent (later 1864-1909) with a composition of .950 Copper and .050 Tin and Zinc unlike the earlier Copper-Nickel Indian Head Cents (.880 Copper and .120 Nickel) and Buffalo Nickels (.750 Copper and .250 Nickel) would be more susceptible to rapid corrosion of the surfaces (fields and details/lettering) which would rapidly eat away at the heavier Copper composition and distort any details and or date. This happens to Buffalo Nickels when trying to restore a Date or Mint Mark but to a slower and lesser extent which can quickly be stopped by a quick dip in Acetone then a fresh water rinse. You could try this with the Bronze Indian Cents but due care must be taken to not allow the corrosive action of the acids to eat to fast into the surface or Details/Date of the coins before quickly diluting it.
Frank