Extreme Drawing

Halloween science experiments for kids (not too scary)

Halloween

Spooky science that's really real

The spookiest things in a kitchen are real science: mould that creeps over food in a few days, a potion that foams out of a bottle, and ghosts that appear when you paint over them. Try them on the screen, then the friendly versions for real.

Play in your browserDo it for real
  • Ages 5+
  • Friendly, not scary
  • With an adult
Painted illustration of a pumpkin with star-shaped holes and mould spots, a bottle foaming over in orange and purple and a pipe-cleaner spider, the painter holding a witch's hat.
Age
5 to 10
Time
20 min, plus a week of watching mould
Mess
Low to medium
Adult needed
For the iron and the foam
You need
Crayons, watercolours, bread, a zip bag
On screen / for real
Both

In Extreme Drawing

A mouldy feast. Squeeze ketchup and honey, drop an egg and some fruit, then tap Wait 3 days on the Time tab. Mould colonies bloom on the food in blue-green, white fuzz, black spots and orange, the fruit shrivels, and fruit flies arrive. Salt shaken on beforehand keeps a patch clean.

A foaming potion. On the Science tab, Eruptions has elephant toothpaste: a fat, stripy snake of foam pushes out of the bottle, and the spot under the bottle gets warm.

A ghost that appears. Draw a ghost with the white crayon, then wash dark watercolour over the page. The wax keeps the paint off, and the ghost shows up white.

A secret message. Write with Secret ink (lemon juice) on the Science tab, then pass the iron from the Toolbox over it. The writing turns brown.

Use the Moon stencil for a night sky. Scratch art (scratching a toothpick through dark paint to the crayon underneath) and googly eyes are in Craft (in the full toolbox).

Play in your browser
Painted illustration of the painter peering through a magnifying glass at bread and a strawberry with fuzzy mould spots, beside a calendar with three days crossed off.

Do it for real

Ghost pictures and a mould jar

For the ghost picture:

  • white crayon (or a candle stub)

  • thick white paper

  • dark watercolour: black, purple or dark blue

  • a big soft brush

For the mould watch:

  • a slice of bread or a piece of soft fruit

  • a few drops of water

  • a zip bag or a jar with a lid

  • sticky tape and a pen

  1. Draw an invisible ghost

    Press hard with the white crayon: a ghost, a bat, a spider web. You can hardly see it.

  2. Paint the night

    Brush watery dark paint over the whole page. The ghost appears, because the wax pushes the paint away.

  3. Set up the mould watch

    Sprinkle a few drops of water on the bread, put it in the bag and seal it. Tape it shut.

  4. Label it

    Write the date on the tape. Put the bag somewhere warm, out of reach of little ones.

  5. Look every day

    Look through the bag, don't open it. Draw what you see: colour, fuzz, where it started.

  6. Throw it away closed

    After a week, an adult puts the sealed bag in the bin without opening it.
Painted illustration of the painter brushing blue watercolour over paper, revealing a white crayon fish and bubbles.

Why it works

For kids: Wax and water don't mix, so the paint slides off the crayon. Mould is a tiny living thing that grows from spores floating in the air. It loves damp food and warmth.

For grown-ups: Crayon wax is hydrophobic and fills the paper's fibres, so a water-based wash can't soak in there (wax resist). Mould spores are everywhere in the air; on damp, sugary or starchy food they germinate and send out threads (hyphae), and the coloured spots are the spore-making parts. Salt and drying hold mould back by taking away the water it needs. Lemon-juice ink browns with heat because its sugars and acids char at a lower temperature than the paper.

Predict first

Wet or dry?

Put a dry slice and a damp slice in two bags. Which goes mouldy first?

Salt

In the app, salt one half of the food before waiting 3 days. What changes?

Coloured crayons

Does a yellow crayon resist the paint as well as a white one?

For teachers

The mould watch fits living things and decay, and microorganisms in KS2 (Year 6 "living things and their habitats"). The app's Wait 3 days lets the class see the result in a lesson, before the real bags have grown anything.

For teachers

What are easy Halloween science experiments for kids?

A crayon ghost that appears under dark paint, a mould watch in a sealed bag, and lemon-juice secret messages that an adult reveals with a warm iron.

How long does it take for bread to go mouldy?

Usually several days to a week in a warm place, faster if the bread is damp. In the app, Wait 3 days shows it at once.

Is mould dangerous?

Some moulds can make people ill, especially people with asthma or allergies. Keep it sealed, don't sniff it, never eat it, and throw it away closed.

Can I make elephant toothpaste at home?

Only the household version, with 3% hydrogen peroxide and yeast, done by an adult wearing goggles. Our elephant toothpaste page explains it.

More spooky science

Grow some mould, on the screen

Play in your browserAll seasons