Because mold spores occur naturally, all one has to do to make a piece of bread turn moldy in theory is to simply wait for it to grow mold, though it is possible to use bottled mold spores to accelerate the molding process. However, some breads made with artificial or natural preservatives may not mold as quickly as those bread products that are made without preservatives, so using a preservative-free bread may result in more successful mold growth. The bread mold experiment is a common simple science experiment for children who are learning about the scientific method, particularly the process of making a hypothesis.
One approach to the bread mold experiment is to seal slices of bread in individual sandwich bags and place them in different locations, including dry, cold places and warm, damp places. This allows children to observe the different environmental effects of various temperatures and levels of humidity, in addition to allowing them to form hypotheses about what conditions will most quickly cause a slice of bread to mold. It is also possible to use both preservative-free bread and bread that includes preservatives in order to observe which one molds most quickly. Exposing bread to different environmental conditions may also cause different kinds of mold to develop.