An incubator may be used to increase the growth. Two plastic drip trays from a garden nursery and a heating pad can be used as an incubator. Do not turn up the heat too high. Choose a spot in the classroom to keep the petri dishes overnight. If using inoculating loops, show students how to clean the loop in a flame between each swab.
Guidelines Have students read the entire activity first.
During the lesson, remind students to label petri dishes as they work, and to make detailed observations. Discuss different methods of controlling microbes.