How to Grow Mold on Bread for a Science Project

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Observe how long it takes mold to grow with this simple experiment
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Interested in doing a fun-gi science experiment for school? Making mold grow on bread is not only a great project for the local science fair, it also teaches the ins and outs of keeping your bread fresh. With a bit of moisture, a little heat, and a bit of time, you'll have a furry green sandwich that will impress your classmates and gross out your friends. We’ll show you how to grow your own mold, how to tinker with the experiment, and explain the science behind common mold.

Running a Bread Mold Experiment

Wash your hands, then use a spray bottle to spritz 1-2 pumps of water onto a slice of plain white bread. Place the slice in a new, unused plastic sandwich bag and seal it. Set the bread somewhere warm and dark, and check it every day for mold growth.

Section 1 of 4:

Growing Mold on Bread

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  1. As with any science experiment, it’s important to have all your materials handy first. Round up the following: a slice of bread (any kind), 1-3 sealable plastic bags, a spray bottle, and water. [1] Any type of bread works, but white bread will show mold the best.
    • Fill the spray bottle with water. A spray bottle isn’t required, but it’s an easy way to evenly coat the bread in a fine mist of water.
    • If you don’t have a plastic bag, use some other sealable clear container instead. Make sure it’s clear so you can watch the mold growth, and sealable to contain the mold.
    • Note that store-bought bread often has preservatives that may make it take longer to grow mold.
  2. Using the spray bottle, lightly mist the bread. You don’t want the bread to be soaked, you just want there to be some moisture to help with the growth of the mold. Just a couple of sprays are sufficient. Or: [2]
    • Place a wet paper towel in the plastic bag with the bread.
    • Sprinkle some water over the top of the piece of bread.
    • Spraying the inside of the bag instead of directly on the bread.
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  3. Place your moistened piece of bread into the plastic bag and seal it closed. For the rest of the experiment, you’ll keep this bag sealed to avoid exposing yourself to the mold spores that will grow on the bread. [3]
    • If you have allergies, you might not want to do this experiment as it may cause you difficulty.
  4. A “control” sample is a basic sample that you haven’t sprayed with water, so you can compare what kind of different moisture makes when it comes to growing mold. Use a clean pair of tongs (so that you don’t introduce germs to the bread with your hands) into a new sandwich bag and seal it. [4] Then, label it with a sticky note that says, “Control,” so you know which bag is which.
    • This isn’t required, but it’s a good idea if you’re growing mold as an experiment for class.
    • If you like, also prepare other samples using our ideas below .
  5. Mold thrives in warm environments with moisture in the air. Find a warm place in your home and store the sealed bread here. You’ve already supplied sufficient moisture to the bread for growth. [5] Keep them out of the sun, though, since it could affect the mold growth.
    • Mold is a heterotroph, so it does not need sunlight to create food. It gets food from the bread itself in the form of starch, which is broken down into smaller sugars. This is why mold often grows in dark, damp areas such as basements. [6]
  6. Each day, take a look at your bread. It should take around 7-10 days before you will be able to see significant mold growth, but you might see growth as soon as 5 days depending on the type of bread you used. [7] Remember, fresh bread will mold faster than store-bought bread containing preservatives. [8]
    • Track the progress by writing notes or taking pictures. When do you start to see mold? What size is the moldy spot? What color?
    • Don’t remove the bread from the bag to examine it. Mold can cause allergic reactions or other side effects, so keep it sealed!
  7. When you’re finished observing the growth of the mold, throw it out. Do not open the bag. [9] Opening the bag can release mold spores into your environment that are not good for your health. It’s also not safe to eat moldy bread under any circumstances.
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Section 2 of 4:

Experimenting with Different Growth Conditions

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  1. Keep all other conditions the same (temperature and amount of light), but add different levels of moisture. [10] Have 1 slice with no moisture, 1 slice that is just damp, and 1 slice that is soaked in water.
    • Check the samples daily to see if the growth of mold is different between the 3 pieces.
  2. To test mold growth at different temperatures, store 1 sample in a warm place (like above the oven), and 1 at room temperature. [11] Then, place 1 in the refrigerator and 1 in the freezer.
    • Remember, to minimize variability, you will want to use the same amount of water for each piece of bread and store the room temperature sample in the dark, as the samples in the fridge and the freezer will mostly be in the dark.
    • Check each sample daily and see which piece of bread grows the most mold the fastest.
  3. If you want to test whether or not light has an effect on the growth of mold, store samples in different light environments. Place 1 bag in total darkness and 1 bag in a brightly-lit area. [12]
    • To minimize variability, make sure the temperatures of both environments are the same. Use the same amount of water for each piece of bread as well. If the amount of water and temperature is also different, you won’t know whether the difference in growth rate is due to the light, water, or the temperature.
    • Observe your samples daily to check for differences in growth rate and amount.
  4. 4
    Use spit or other substances to grow mold. Mold often grows faster if there are more germs, or food, to eat up! Mix up your experiment by using your own spit instead of water. Or, simply wipe your hands on the bread before bagging it and see what happens. Just remember to use a control sample that you haven’t done anything to to compare it to! [13]
    • Or, sprinkle the bread with lemon juice, sugar, or wipe a dirty object on it, like a TV remote.
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Section 3 of 4:

Mold FAQs

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  1. 1
    What is mold? Mold is a kind of fungus that grows from spores. You’ve probably seen it on old food in your fridge. Mold reproduces by releasing spores that, if the conditions are right, grow into mold cells. Molds are heterotrophs, meaning they eat other organisms for energy. When you see mold on your food, it’s eating that food before you get a chance to! [14]
  2. 2
    Is mold a bad thing? Mold is gross, but it’s also super helpful! Mold eats and breaks down organic materials like food or dead plants to create nutrients that other living things need to survive. We need mold to break down those dead things and to feed things like plants. That said, lots of mold is harmful to humans if we touch or eat it. [15]
    • Some molds aren’t very dangerous, though. Many kinds of cheese are made by growing mold in the cheese on purpose, changing its flavor and other qualities. [16]
  3. 3
    What happens if you eat moldy bread? Experts say you’ll most likely be alright, but that you still shouldn’t risk it. Eating moldy bread can cause illnesses and symptoms like stomachaches, fever, nausea, diarrhea, or allergic reactions that may require medical attention. [17]
    • If you eat moldy bread, keep an eye on your symptoms. If you still feel sick 24 hours after eating the moldy food, talk to a doctor ASAP.
  4. 4
    Why don’t some foods mold very easily? Some foods have preservatives added to them to make them last longer. These preservatives often make it harder for mold to grow, so the food stays ready to eat for longer. Food that doesn’t have preservatives, like food you make at home, will often mold more easily. [18]
  5. 5
    Why does mold sometimes look different? That’s usually because they’re different kinds of mold! You often see green-blue mold grow on bread or citrus fruits, while white mold grows on strawberries, and black mold grows in the shower. There are thousands of different kinds of mold, and different molds prefer different food sources and conditions. [19]
  6. 6
    Can you just cut off the moldy parts of the bread? The answer is no. It may look like the mold is only on one part of the bread, but bread is soft and airy, making it easy for mold to spread inside. Even if you can’t see mold in other parts of the bread, there’s probably invisible mold spores you can’t see that are still harmful. It’s best to throw it out. [20]
  7. 7
    How do you store bread so it doesn’t mold? For best results, store your bread in a paper bag, with the cut side facing the closed end of the bag. Then, store the bread in a bread box, which stabilizes things like light, heat, and humidity. If you don’t have a paper bag or bread box, store the bread in a sealed plastic bag on the counter, away from sunlight. [21]
    • Keep your bread in a sealed plastic bag and place it in the freezer to keep it fresh for later. When you want to eat it, pop it in the often at 325 °F (163 °C) for 20 minutes to make it warm and soft again.
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Section 4 of 4:

How long does it take for bread to mold?

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  1. Mold can grow on bread in 5-10 days. That said, there are a lot of variables! Some breads, like fresh-baked breads, mold more easily than others, since they lack preservatives. Other breads, like challah, are more moist, so they grow mold faster. It all depends on the kind of bread and the conditions in which you store it. [22] b
    • To make bread last longer, store it in a cool, dry place, like a pantry, where mold has a harder time growing.

Expert Q&A

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  • Question
    What will happen if I don't seal the bags?
    Meredith Juncker, PhD
    Scientific Researcher
    Meredith Juncker is a PhD candidate in Biochemistry and Molecular Biology at Louisiana State University Health Sciences Center. Her studies are focused on proteins and neurodegenerative diseases.
    Meredith Juncker, PhD
    Scientific Researcher
    Expert Answer
    If the plastic is not sealed, your bread may dry out. Mold needs moisture to grow. Additionally, an open bag may cause the spread of mold spores into the atmosphere which can be potentially harmful to the human body.
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  • Question
    Can mold be used as a medicine?
    Meredith Juncker, PhD
    Scientific Researcher
    Meredith Juncker is a PhD candidate in Biochemistry and Molecular Biology at Louisiana State University Health Sciences Center. Her studies are focused on proteins and neurodegenerative diseases.
    Meredith Juncker, PhD
    Scientific Researcher
    Expert Answer
    While some pharmaceuticals are derived from mold (e.g., penicillin), regular mold cannot be used as a medicine as is. You would need to know the type of mold you have (species name) and would also have to process the mold scientifically to create a medicine suitable for human use.
    Thanks! We're glad this was helpful.
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  • Question
    How long does it take for mold to grow on the bread?
    Community Answer
    Lightly moistened bread stored in a warm, dark place should grow mold in about 7-10 days.
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      • If you have allergies, don't do this experiment because it could trigger a reaction for you. Wear a face mask just in case.
      • Keep the moldy bread away from children or pets that may eat it and get sick.
      • If you're using a plastic container, throw the container away as well.
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      Warnings

      • The mold on bread can be highly toxic to dogs. Ensure your dog does not eat mouldy bread or come into contact with plates, dishes, etc that mouldy bread has touched.
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      • DO NOT eat the moldy bread, smell it, or even take it out of the bag indoors. The mold releases tiny spores into the air that may trigger allergies and spread the mold onto surfaces and food that you do not want to grow mold on.
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      • Penicillin grown on bread cannot be used to treat illnesses or infections.
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      References

      1. ↑ https://www.mottchildren.org/posts/camp-little-victors/dirty-hands
      2. ↑ https://www.csun.edu/scied/2-longitudinal/long_research/
      3. ↑ https://sciencekids.in/bread-mold-science-project/
      4. ↑ https://behrend.psu.edu/files/pdf/51106/2020/05/28/bread-and-mold-experiment.pdf
      5. ↑ https://case.fiu.edu/education-outreach/fiuhome/create/experiments/2020/create-a-bread-petri-dish-experiment.html
      6. ↑ https://milnepublishing.geneseo.edu/botany/chapter/rhizopus/
      7. ↑ http://www.microscopy-uk.org.uk/mag/artnov14macro/Brown_Ryan_Mold.pdf
      8. ↑ https://case.fiu.edu/education-outreach/fiuhome/create/experiments/2020/create-a-bread-petri-dish-experiment.html
      9. ↑ https://www.anecdata.org/projects/view/718/pages/63
      1. ↑ https://www.scienceprojectideas.org/bread-mold-experiment.htm
      2. ↑ https://www.open.edu/openlearn/mod/oucontent/view.php?id=96039&section=_unit3.9
      3. ↑ https://www.open.edu/openlearn/mod/oucontent/view.php?id=96039&section=_unit3.9
      4. ↑ https://outsideinradio.org/shows/moldandmoss
      5. ↑ https://milnepublishing.geneseo.edu/botany/chapter/rhizopus/
      6. ↑ https://milnepublishing.geneseo.edu/botany/chapter/rhizopus/
      7. ↑ http://www.microscopy-uk.org.uk/mag/artnov14macro/Brown_Ryan_Mold.pdf
      8. ↑ https://health.clevelandclinic.org/what-happens-if-you-eat-moldy-food
      9. ↑ https://case.fiu.edu/education-outreach/fiuhome/create/experiments/2020/create-a-bread-petri-dish-experiment.html
      10. ↑ http://www.microscopy-uk.org.uk/mag/artnov14macro/Brown_Ryan_Mold.pdf
      11. ↑ https://www.npr.org/sections/thesalt/2017/04/21/523647669/is-it-safe-to-eat-moldy-bread
      12. ↑ https://www.npr.org/sections/thesalt/2017/04/21/523647669/is-it-safe-to-eat-moldy-bread
      13. ↑ https://pmc.ncbi.nlm.nih.gov/articles/PMC8834264/

      About This Article

      Article Summary X

      To make mold grow on bread, all you need is a sealable plastic bag and water. Start by dampening a slice of bread so the mold will grow quicker. You can do this by spraying the bread with a bottle, dripping water on it, or placing a wet paper towel on it. After that, seal the damp bread in a plastic bag and store it somewhere warm. The bread will start to get moldy within 7 to 10 days. The fresher your bread is, the faster it will get moldy. This is because fresh bread doesn’t have preservatives like cheaper bread. For more tips from our Science co-author, including how to test different samples of bread, read on!

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