Thanks for the responses. One of my questions remains, if a double was improperly hot blued, would a proper rust bluing remove/neutralize any residual salts from the hot caustic bluing? I was told by a well recognized smith that if the gun is not presently showing a loose rib at this time the rust bluing will neutralize and or remove the residual salts from the hot caustic blue and help insure the guns ribs remain tight to the barrels. I looking for confirmation or not.