Where does mold come from, and what...

... do I do about it?
Mold is an unfortunate fact of life. If there‘s a spore, and the conditions are right, the spore will germinate, and you‘ll get mold. If tobacco is too damp, there‘s a much greater risk of mold, but mold can form even on fairly dry substrates. Most commonly, mold develops when tobacco has dried out, been over-hydrated, and put in containers that are not clean. I‘ve often read about using a little vinegar in the water used to rehydrate the tobacco, in order to retard mold. This is a myth. I‘ve seen some pretty dramatic mold formations on tobacco that was literally doused with vinegar. And, besides, tobacco treated this way will taste like vinegar.
Some molds really stink, and even a small colony will render the entire batch unsmokeable. Others are quite innocuous, and removing the damaged area before the mold is allowed to spread will possibly spare the rest of the tobacco.
If you store tobacco in a jar, and end up with a good case of mold, there‘s no need to throw out the jar. Just wash with hot, soapy water with a little bleach, and rinse thorougly. If you have a dishwasher, it‘s a good way to get the jar squeaky clean and ready to use again.

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