Petri dishes are a common item found in both professional and educational science labs. Unfortunately, budget restrictions force companies and educational establishments, such as high school and college biology labs, to reuse the Petri dishes. The disadvantage of reusing Petri dishes is the increased ability to contaminate your current experiment's culture with remnants from the previous experiment. However, there are various sterilization methods available depending on if your Petri dishes are glass of plastic.
How to Sterilize Petri DishesBy Travis Wampler