Choose bread that is highly refined and will break down quickly when exposed to moisture. Refined breads are made with white flour, such as sandwich bread, pastries, donuts or cakes. Avoid using breads that contain preservatives or ingredients designed to prevent molding or caking. This can affect the outcome of your experiment. Homemade white bread works best.
Adding mold spores onto the bread can help encourage the mold to develop more quickly. You can add mold spores to your bread sample by soaking the end of a cotton swab in water, wiping a kitchen counter top or bathroom sink, and then wiping the wet swab onto the bread. The moisture from the swab will also promote mold development on the bread.
The bread should be sealed in an air-tight container with a small piece of paper towel or cotton that is slightly dampened. A sealable plastic bag works very well at keeping out air, and will allow you to easily see the development of mold on the bread sample. Avoid using plastic wrap, which can allow air to get into the sample. This can dry out the bread and delay the bacterial mold from developing.
Place the bread in a warm, dark location that is out of direct sunlight. If the sample is warm and in the dark, mold will develop more quickly and readily. It is ideal to place the sample near a cabinet that is dark and next to a water heater or an oven. Leave the bread in its location for about a week to allow the bread to develop sufficient mold on it.