The Science of Foaming wine rainbow

The liquid in the bottle here is not actually wine, of course, it is a special liquid called "cabbage juice"!

Cabbage juice is normally red. However, it contains chemicals like those you may have seen in litmus paper in your school laboratory. These chemicals change colour depending on how acid or alkali the liquid they are in is - red for acids and blue for alkalis.

This cabbage juice starts out very slighlty acidic so it is red. However, the white powder is bicarbonate of soda which is alkali. So, not only does it react strongly to produce the foam, but it also changes the colour of the indicator chemicals to make then pink and then blue.

Strong acids and alkali are very dangerous, but the acids and alkalis used here are very mild and safe to use.