Is there a reason why lather is always white no matter what color the soap, shampoo or detergent is?

Because you are seeing reflected light, and typically the light source in your bathroom/kitchen is white light from a bulb or from sunlight. ';Color'; is perception based on the reflected wavelengths of light; surfaces absorb some wavelengths and reflect others. We see the reflected wavelengths. When something ';looks'; white it is typically because it's reflecting all or almost all wavelengths of light.Is there a reason why lather is always white no matter what color the soap, shampoo or detergent is?
Lather some up just a little and estimate the reflectivity of the individual bubbles. Looks like 20% or so. In penetrating just the outer 0.01 inch or so of the fully developed lather structure a light ray encounters many of those surfaces, each reflecting a further percentage of the light that reaches that far.


The shampoo coloration isn't very dense when you look at it in the bottle. The lather is perhaps 10% shampoo and 90% air. So as it is being successively more totally reflected, the light ray passes through only a microscopic thickness of actual shampoo. As another answer said, if the incident light is white, that's what you'll see reflected as the apparent color of the lather.Is there a reason why lather is always white no matter what color the soap, shampoo or detergent is?
I think I've seen green lather with like pert plus or something...





I don't know- interesting question though!