Science Buddies: "Ask an Expert"

Hello, I am currently preparing to conduct the“Bacterial Resistant Materials and the Best Disinfectant” experiment, and I’m not sure if I’m understanding the procedure correctly. Are you supposed to introduce bacteria to the cleaning materials in the first half (like using a piece of an old used sponge) or are you supposed to use clean, new supplies and incubate them in saline and just see if bacteria forms? I don’t see how bacteria will grow if everything is clean to start with.
Here’s the experiment: https://www.sciencebuddies.org/science- ... sinfectant
Thank you in advance

Hi there!
I just read through the procedures and you are supposed to use dirty/used/old sponges, rags etc. for the first part. It seems that whoever wrote this assumes that the experimenter would have these items on hand. If you don't have enough samples, I would suggest reaching out to a friend or a neighbor who has used cleaning materials. Good luck with your experiment. Please reach out with any questions. Cheers.