|MadSci Network: Microbiology|
Most molds require some water, some nutrients, a warm enough temperature, and an environment without a lot of competition from bacteria to grow really well. Most molds do not require light to grow because they do not use photosynthesis like plants do. They will also grow over a very wide range of temperatures. At cooler temperatures they will still grow, but will take longer than at warmer temperatures. To get really good mold growth on bread, choose a bread that does not contain preservates like propionates. These are added to the bread specifically to inhibit spoilage microorganisms such as molds. A fresh loaf of bakery or home-made bread usually work very well. Put the bread in a plastic bag along with about 10 milliters of water and a light dusting of soil. Close the bag enough to retain the moisture and put it in a drawer or other dark area. In a few days you should be able to see some very good mold growth.
Try the links in the MadSci Library for more information on Microbiology.