What Makes the Truth Beads Change Colour?

The Truth Beads contain special chemicals called photochromic pigments.

Indoors, these pigments are almost colourless, so the beads appear white.

But outside, something invisible reaches the beads and causes the pigment molecules to change.

That invisible energy is ultraviolet radiation, or UV.

Why Does UV Change the Beads?

UV radiation carries energy.

When UV reaches the photochromic pigment, that energy changes the arrangement of its molecules. In this new form, the pigment absorbs some colours of visible light and the bead suddenly appears coloured.

Take the beads away from the UV and the molecules gradually return to their original form.

The colour fades.

That is why your beads can change again and again.

Why Didn't the Paper Stop It?

This is where the experiment becomes interesting.

Paper is very good at blocking visible light. That's why you cannot normally see straight through a sheet of paper.

But visible light and ultraviolet radiation are not the same thing.

Some UV can still reach the beads depending on the paper, its thickness and the conditions of your test.

Your eyes might think the beads are safely hidden...

but the beads can reveal radiation you cannot see.

What Did the Sunscreen Do?

Sunscreen contains ingredients designed to reduce the amount of UV radiation reaching your skin.

Your sunscreen-covered bag should therefore have exposed the beads to less UV than the uncovered control.

But look carefully at your results.

Did the sunscreen stop the colour change completely — or simply reduce or slow it?

That's an important scientific distinction.

Scientists Say...

UV radiation is part of the electromagnetic spectrum.

We cannot see UV with our eyes, but we can detect its effects.

Your Truth Beads acted like tiny UV detectors, turning something invisible into evidence you could actually observe.

And that raises an even bigger question:

If UV is invisible, how do scientists measure it — and what can it do to living cells?