Hermione is trying to replicate the Polyjuice Potion that they created in their second year at Hogwarts. The problem is that she doesn't have the exact ingredients that she needs and she is trying to substitute imitation bat wings instead of real bat wings. She knows that they are not as strong as the original so she is making three separate batches using the same type of cauldrons for each batch. She will also use the same fire so she can test which amount of imitation bat wing will work. The potion will turn green when the correct amount is added.