It's been a while since I've interpreted delta 13C measurements but it seems like adding 13C could mimic older materials, however you are correct about 14C unle

It's been a while since I've interpreted delta 13C measurements but it seems like adding 13C could mimic older materials, however you are correct about 14C unless you want to make something modern look like its ~1960s era. You would need to reduce 14C (either by dilution with depleted ethanol [quick search doesn't find a source for this] or somehow purify the scotch itself) to make it look pre-1950s.