[in Spanish]

KidZone Science
How Does Mold Grow?

© Contributed by Leanne Guenther

This experiment uses 4 samples to test what conditions mold grow the best in.  Depending on the age of the child(ren) you can use only 2 or 3 samples instead of all 4.

What you need:

Safety Thoughts:

  • Some people are allergic to molds.  If this is a concern, skip the first sample (just use the last 3) and seal each of them in a clear glass jar, so the child(ren) can examine them without being exposed to the molds.


  • SAMPLE 1:  Take a piece of bread and slice it in half (it can be a few days old, but ensure it isn't too stale).  Seal one half in saran wrap and expose the other to air.   
  • SAMPLE 2:  Take another piece of bread and slice it in half.  Leave one half in the dark (a paper bag or cupboard) and the other half in strong light (sunlight works)
  • SAMPLE 3:  Take a third piece of bread and slice it in half.  Keep one half very dry and put about 1 tsp of water on the other half.  (Spritz the wet piece with a few drops of water each day).
  • SAMPLE 4:  Take a fourth piece of bread and put half of it someplace warm, in the dark (on top of the fridge in a paper bag) and the other half someplace cold in the dark (the refrigerator).
  • Examine the samples each day with your naked eye or a magnifying glass and record any changes in appearance. 

What happened:

Molds will develop on some of the samples.

Molds grow best in warm, dark and moist conditions.

In the first sample, the sealed bread should develop mold more slowly than the unsealed bread.

In the second sample, the bread kept in darkness should develop mold more quickly than the bread kept in light.

In the third sample, the moist bread will develop mold more quickly than the dry bread.

In the fourth sample, the mold in the warm place should develop mold more quickly than the bread in the cold place.

Questions to Ask:

  1. Where and how should bread be stored to keep it free from molds?
  2. What other foods do you think might grow molds if left exposed?
  3. What are some ways that people use to preserve their food?


Possible Answers:

  1. someplace sealed, in the refrigerator, in the light, someplace dry, someplace cool
  2. cheese, oranges, tomatoes, lemons, onions, used coffee grounds, potatoes  (determining what foods mold the best can be an entirely different experiment!)
  3. refrigerator, artificial preservatives, natural preservatives like vinegar and salt, tupperware