Why is lather of soap always white?

Answer 1

There are two things at work, here:

The first has to do with way the light that is reflected. The spherical bubbles reflect all colors, the achromatic sum of which is white. This is the same as a cloud on a sunny day, where water particles work the same way as the bubbles and give the cloud a white appearance.

The second has to do with the density of the particulate in the water; keep in mind that, other than the particulate floating in the water, the water itelf is clear. Once it is broken down to a foam, the colored particles are diffused. This is the same as grinding up a colored substance; if you grind it fine enough relative to the particles which color it, it will turn white.

Answer 2

There are two things at work, here:

The first has to do with way the light that is reflected. The spherical bubbles reflect all colors, the achromatic sum of which is white. This is the same as a cloud on a sunny day, where water particles work the same way as the bubbles and give the cloud a white appearance.

The second has to do with the density of the soap; once it is broken down to a foam, the colored particles (in this case, dye) are diffused. This is the same as grinding up a colored substance; if you grind it fine enough relative to the particles which color it, it will turn white.

Please see Color and Foam in Nature by David K. Lynch, William Charles Livingston: [related link]

Answer 3

See related question for the answer.

Answer 4

The surf :)