How to Place the Inoculated Agar Plates in Inverted Positions
- 1). After pouring the sterilized agar into the sterilized Petri dish, immediately place a cover on it to prevent contamination.
- 2). Hold the covers on the Petri dishes gently but firmly as you invert them. The agar will be solid enough to adhere to the bottom of the dish.
- 3). Place the agar plates carefully upside down on a rack to give the agar sufficient time to cool and solidify. They can be stacked in this position. Placing them upside down prevents any condensation that might accumulate on the cover from dripping onto the agar itself. If they will not be used immediately, they should be stacked in an inverted position in a refrigerator.
- 4). Inoculate the agar plates with bacteria or other cultures as required by the experiment or lab test. Replace the cover of the Petri dish immediately to prevent contamination from airborne organisms. Immediately turn the agar plate upside down again.
- 5). Place the inverted, inoculated agar plate inside an incubator carefully. Make sure to place it level and keep it inverted. They can be stacked in this manner. The inverted position prevents any moisture loss to the inoculated agar plate. In addition, it prevents condensation from dripping onto the agar, which can spread microorganisms erratically on the medium, skewing the results of the experiment or lab test.