Dirty Hands Bread Experiment

This was a really neat experiment to do to learn about germs and how they spread! It was really interesting and GROSS at the same time! If you have little ones that hate washing their hands, this experiment is a great visual aid as to why it is important!

Here is what you will need:

Start with three pieces of bread – one will be the control, one will collect unseen stuff (bacteria, viruses, mold spores) from dirty hands, and one will collect that stuff from clean hands. For this experiment, we picked bakery fresh bread that had no preservatives, which would slow down the mold formation.

Did you say mold? That’s right. Throughout this experiment, we will be growing mold spores on each piece of bread. While mold spores aren’t a virus or bacteria (they’re actually fungi!), they are what we use in this experiment to show us just how dirty our hands can become throughout the day. According to the CDC, mold is everywhere, even in the air and on common area surfaces. Remember, illness causing bacteria and viruses are also found on common surfaces that we touch throughout the day, so by the end of this experiment, we’ll be able to see just how much gross particles are on dirty and clean hands. Now, let’s get back to the experiment!

The first piece of bread will be your control, which you’ll place in a sandwich bag using plastic gloves later on in the experiment. If you've forgotten a few things from science class, a control is something that is used as a standard comparison to check the results of the experiment. In this case, we want to see the pace and types of mold that grow on a piece of bread that was not exposed to skin contact as compared to the other pieces of bread that were touched with clean and dirty hands.

The next piece of bread will be the one you touch with dirty hands. Make sure to not wash your hands for a few hours before you touch this piece of bread – and by all means, touch the bread all over with your hands. We went a little further by touching things we thought would have the most germs, trash cans, door knobs, toilet, and sinks!

The last piece of bread will be the one you touch after you have thoroughly washed your hands.

Before placing each piece of bread in its own sandwich bag, spritz the bread with water from a misting bottle. If you remember from your high school science classes, mold needs water to grow and cannot survive without a source of water. In addition to water and moisture, warm temperatures, oxygen, and particular pH levels also create a favorable environment for mold growth. Once each slice is spritzed with water and placed in their bag, seal the bags tightly and label each piece accordingly.

Now for the best part, we wait. If you’re following along at home, take pictures now to mark Day One of your experiment.

For this experiment, we recommend checking in on your pieces of bread every other day for more apparent results. When Day Three came around, we had yet to notice any visible growth. Day Five was a different story.

By the time day ten rolled around, we noticed mold growing on the dirty hands sample. We used white bread, which was probably why it wasn't a huge amount of mold as compared to the original experiment (the bleaching process during baking make it a little more difficult for germs / mold to thrive. )

We also used a "Germ Mapping" and "My predictions" journal worksheet to really explore germs, open discussion and record our hypothesis, and results.