Wash your hands and wear gloves
Cut a raw potato into thin slices
Place the slices on a clean plate or in a sterile container
Lightly moisten the potato slices with sterile water
Expose the slices to a source of bacteria, such as a swab from a dirty surface
Keep the slices covered loosely to reduce contamination while allowing air exchange
Store them in a warm, dark place
Check for growth over several days
Dispose of the potato slices and clean all surfaces after observation