Garum
Experimentbeginnerdraft

Red cabbage colour magic

Also searched as: red cabbage experiment, acid test, pH experiment for kids, red cabbage indicator

In short: Red cabbage juice shows by its colour whether something is acidic or alkaline.

Picture it

Like a chameleon in a glass: the pigment changes colour depending on its surroundings.

Before · Afterred cabbage juice
with vinegar
nothing added
with baking soda
Schematic
You need · 15 minutes
  • a few red cabbage leaves
  • hot water
  • three glasses
  • vinegar or lemon juice
  • baking soda

Hot water: adults do the pouring.

How it’s done

Sequence · Step 1 of 4
1234

Chop red cabbage, pour hot water over it and let it steep for 10 minutes.

All steps as a list
  1. Chop red cabbage, pour hot water over it and let it steep for 10 minutes.
  2. Divide the purple juice between three glasses.
  3. Add vinegar to one glass and a pinch of baking soda to another; leave the third as it is.
  4. Compare the colours.

What you see

With vinegar the juice turns pink to red, with blue to green; with nothing added it stays purple.

Why it happens

The pigments in red cabbage () change shape with the . That is why apple or vinegar belongs in red cabbage if it is to stay red.

Related entries
Acid (lemon, vinegar)
Sources · 1
  • Harold McGee: On Food and Cooking (2004)