When I’m in the shower, sometimes I’ll notice my hair is particularly greasy and once I’ve rinsed off the first round of shampoo, I’ll apply a second round. And no matter how small of an amount I apply the second time around, it turns into a baby bubble bath commercial with oodles of suds and bubbles and foam all over the place?
Is it because the first lot got used up on a larger bulk of grease and the second amount doesn’t and so it can bubble up more?
In: Chemistry
Shampoo molecules have one end that binds to water (hydrophilic head) and another one that binds to sebum/grease (hydrophobic tail).
Bubbles form because the shampoo molecule reduces the surface tension of the water when it binds to it. But when it also binds to something else on the other end it cancels out that effect.
During the second round most tails have nothing to bind with, so a lot of bubbles can freely form.
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