Handbook of Nature-Study · Lesson CLXXXVI · Topic 27: Mushrooms, molds and bacteria
186. Molds
Goal: Your child sets up a safe sealed mold experiment and finds out which conditions mold likes best.
You'll need
- 4 squares of bread (bakery or homemade bread molds fastest)
- Zip-top sandwich bags and tape
- A permanent marker
- A few drops of water
- A hand lens (magnifying glass)
- A nature notebook and a pencil (colored pencils if you have them)
What's in the book
The lesson describes an experiment with bread squares kept moist or dry, in a warm dark place or a sunny dry place, and fruit juice with and without dust, then eight observations on when and how the mold grows.
The lesson, step by step
The leading thought
The spores of mold are everywhere and help to make what we call dust. These spores will grow on any substance which gives them nourishment, if the temperature is warm, the air moist and the sunlight is excluded.
Set up the experiment
Follow the book's plan, but seal each piece in its own zip bag instead of covering it with a tumbler:
Use four pieces of bread cut in about two-inch squares, each placed on a saucer; moisten two and leave the other two dry.
Touch each piece lightly with a fingertip of dust from a shelf. Seal and label each bag. Put one moist and one dry piece in a warm, dark cupboard, and one of each on a sunny windowsill.
Safety rules for mold
The bags stay closed for the whole experiment, and in the end they go into the trash still sealed. We don't open them or sniff them, because mold spores can make people sick or set off asthma and allergies. If anyone in the family has those, keep the bags well away from them.
Check every two or three days
Look through the bag with the hand lens.
When does the mold begin to appear? Which piece of bread showed it first? Describe the first changes you noticed. What is the color of the mold at first?
Did the mold fail to appear on any of the pieces of bread? If so, where were these placed? Were they moist? Were they exposed to the sunlight?
Colors and kinds
Did more than one kind of mold appear on the bread? If so, how do you know that they are different kinds? Are there any pink or yellow patches on the bread? If so, these are made by bacteria and not by mold.
Sum it up
From the results of the experiments, describe in what temperature mold grows best. In what conditions of dryness or moisture? Does it flourish in the sunlight or in the dark?
Where does the mold come from? What harm does it do? What should we do to prevent the growth of mold?
What we know now
Molds are fungi, not plants. Some molds are useful: one of them gave us penicillin, the first great germ-fighting medicine. Store-bought bread often has ingredients added to slow mold, so it may take longer.
Nature notebook
Make a chart with a row for each bag and a column for each day you check. Draw what you see. At the end, write one sentence on what mold likes.
Afterwards
Check the bags every two or three days for about two weeks, then throw them away sealed.
Answers to the book's problems
Mold grows best on the moist bread in the warm, dark place; it grows little or not at all on dry bread and in sunlight. Its spores float in the air and dust everywhere. Keep food cool, dry and covered, and eat it before it spoils.
Worked out for this site from the scan. If a number in your copy differs, trust the book.