The illusion of the silver egg

Is the silver color of the egg real or an illusion?

Some alchemists claimed to be able to turn lead into gold. Nicolas Flamel, a 15th-century French alchemist, was working on it, convinced that it was possible. Alas, he never succeeded! In his image, you will make the shell of an egg shine like silver. The illusion of the silver egg is explained by science, of course.

You will need:
  • A fresh egg
  • A glass jar full of water
  • A candle
  • A lighter
  • A grill tongs

From 8 years old

Difficulty : medium

This experience requires the help of an adult

Let's experiment

egg on a flame

Light a candle and ask an adult to hold the egg over the flame

egg on a flame with soot

As soon as the first black spots of soot appear, move the egg until its entire surface is covered with soot.

egg covered with soot

Do not forget the tops of your egg so that they too are covered in soot.

Illusion of the silver egg

Fill a glass jar with water and carefully dip your egg into it.

TADAM! Silver reflections appear immediately once the egg is in the water.

Understand the experiment

The illusion of the silver egg

When the candle is lit, the egg becomes covered with soot. Soot is a mixture of compounds produced by the burning of the eggshell. It contains mainly carbon, which gives it its black color. This carbon is in the form of extremely fine dust that hates contact with water. These are called hydrophobic particles.

Also, when you dip the egg in water, it carries with it microbubbles of air to reduce contact between the soot and the water. These microbubbles form a film of air that acts as a mirror once in the water.

The outside light that arrives on the egg encounters different media. The light passes through the water and then the air before arriving on the egg. These changes of medium influence the propagation of light. It changes direction. But depending on the angle of incidence, it can be totally reflected. It is the total reflection of the light that gives you the impression of having a silver egg. But when you take the egg out of the water, it is black and dry!

An illusion that exists only in water.

If you take your egg out of the water, you will see that it is all black! Soot is hydrophobic and induces a surface tension with water but not with air. The magic of the process lies in the choice of the liquid to make the silver reflection appear. The less the soot likes the liquid, the more pronounced the silver sheen will be.

Challenge

Will the egg be silver in another liquid?

To find out if soot soothes in its environment, test different liquids. Oil, vinegar, colorless soda … and record your observations. Does the silver egg illusion work in other fluids?

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