Warm, humid places speed mold growth; cool, dry places slow it.
Refrigeration delays mold but makes bread stale faster. Freezing is best for long-term storage.
For short-term storage, paper or cloth bags are better than plastic, which traps moisture and encourages mold. Artisan bread stores well in paper and freezes well; sandwich bread lasts longer in sealed plastic.
To sum up, stale bread is safe and useful, but moldy bread should be discarded. With proper care, you can enjoy your bread longer and reduce waste.
