No mold so far. I was even surprised that one of the jars that was half empty (i.e. with air in the jar) hadn't molded over yet. Normally I keep the bottles full by transferring down to smaller bottles as I use it up, to keep the air (and thus the mold) out. Black walnut is naturally anti-fungal, though I do use whole cloves as a precaution (oil of cloves would work, too). I don't think I'm going to use alcohol at all any more, though I'll wait and see how the last batch does over time before deciding for sure. The only batch that ever gave me mold trouble was the cold-process (uncooked) one, but as long as I keep the air out, those bottles do fine, too.
Edited by fiberdrunk, 19 June 2014 - 21:21.