Will red wine vinegar grow mold?
It is not likely. Vinegars are very acidic which retards mold (molds are fungi, similar to yeast.) Natural vinegars are cultured from "vinegar mothers," which are acetic acid bacteria,sometimes seen as cloudy, slimy areas in vinegar. Although balsamic vinegar in not as acidic as other vinegars, most brands probably would not support bacteria. Because products called "balsamic vinegar" are not aged, and some contain sugar as well as preservatives, it is difficult to give a firm answer for all varieties.