Why Do Different-Colored Shampoos Make the Same White Foam?

Have you ever notice how no matter the color of the shampoo you use, the foam we get is always white in color? Find out the reason behind that in the five answers below.


Because the bubbles that make up the foam are so thin that the pigments that make up he color are too thinly spread to matter much. Instead the light is fractured everywhere by every bubble making it effectively reflecting white light.


Anyway it’s because the colour gets spread so thin and infused with microbubbles that the colour pigment makes no difference to the light hitting it so it appears white.Darker colours will reduce this effect. An entirely black shampoo would have very dark suds.


The reason shampoo turns white when lathered is because the air bubbles that are created spread the coloring of the shampoo so thin, that it becomes translucent and when you have multiple bubbles stacked the way lathered shampoos appears, our eyes perceive it as white.


Not quite right. Even if the coloring is spread thin, several bubbles should give it its color back again. The actual reason, as far as I know, is that each bubble scatters the incident light in rainbow patterns, in the same way that soap bubbles do (due to interference over a thin film). Add enough of these, and you have a whole bunch of small, random scatterings of colors. White light is simply a mix of all colors, so that is what you will see when you look at the foam.


The dye chemical tends to not want to hang around in the very thin soapy matrix that forms the bubble wall. Then, if you do have a dye that will work, it still takes a fairly high concentration of it to be visible. That’s a problem because when the bubble pops it leaves a dark dye stain behind.

Fortunately, dyes have been invented specifically for this purpose and are used in the Zubbles product. You might enjoy reading about the development of the dyes if you’d like a somewhat deeper look at the challenges that colored bubbles present.


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