Why is lather always white

Lather or foam is nothing but a large collection of small soap bubbles. A soap bubble is, in turn, a very thin film of soap solution enclosing some air. Because of the low surface tension of soap solution, the film can stretch and spread and form innumerable bubbles with a very large total surface area.

Due to this, whatever slight tint is present in the thin film of the coloured soap solution gets subdued. Although a soap film is more or less transparent, the lather or foam looks white because the light striking this large collection of bubbles gets scattered. That is the reason why all kinds of lather or foam appear white.

Natural or handmade soaps may expire sooner, within one year, as the essential oils and fragrances can get rancid or moldy. When formulating your recipe, consider the cheaper soaping oils. Some of the most cost-effective soaping oils are canola, castor, coconut, olive oil pomace , palm oil, rice bran oil and sunflower oil.

These oils still make a great bar of soap. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Coursework Why is soap lather always white? Ben Davis April 28, Why is soap lather always white? Why is shampoo foam white? Why are hair shampoos indifferent Colours and the foam always white? Why soap is Coloured? Why do soap bubbles change color? Why do soap bubbles look colorful? What soap bubbles do? Although a soap film is more or less transparent, the lather or foam looks white because the light striking this large collection of bubbles gets scattered.

That is the reason why all kinds of lather or foam appear white. The light rays that are reflected off the inner surface of the bubble travel further than the light rays that are reflected off the outer surface. The iridescence of a soap bubble, which seems to contain a wealth of changing color, stems from light striking the bubble from varied angles. A bubble pops when the water that is trapped between the layers of soap evaporates. The glycerin or corn syrup mixes with the soap to make it thicker.

The thicker skin of the glycerin bubbles keeps the water from evaporating as quickly, so they last longer. Some examples of nourishing soft oils in a soap recipe are high oleic sunflower oil, high oleic safflower oil, olive oil, canola oil, almond oil, apricot kernel oil, and avocado oil.

Luxury soft oils include oils like evening primrose oil, walnut oil, wheat germ oil, hemp oil, rosehip oil, and pumpkin seed oil. You'll see that the soap, apart from making it more cloudy, has not visibly imparted any particular color to the water.

This is not unexpected, as I've already mentioned, the quantity of dye used is very small. Now if you go ahead and agitate that soap solution, it will give rise to white lather, and this shouldn't be surprising anymore. But this is grossly incorrect.

While TIR can result 'white light', it is not the dominant phenomenon acting here I'm not saying it's completely absent here either. What is largely giving foam it's white appearance is another phenomenon called Scattering.

Now you might ask, 'Then why isn't soap water white? Well, since the foam is made up of lots of teeny tiny bubbles, light passing through it will have to encounter several surfaces, and it's these surfaces that scatter the light in so many directions. Remember I said you can't see any visible coloration in the water because of the dye is present in really small quantities? Well here's a way to validate that claim: Simply combine a teaspoon of red food-color with a bit of hand-wash now that's really concentrated.

Now you can lather the soap and lo behold! You have red foam. SE, for that bit on why soap water isn't white. Also he confirmed that the white color of foam is due to scattering].

Edit- More kudos to ACuriousMind for providing this amazing link on scattering. This is because the color has been diluted to a great extent that it basically became transparent. You would observe that the unorganized mass of transparent particles the bubble is quite organized would appear white. Another example; a small water column when you open the water tap organized is transparent, but when you open the water tap to a greater extent, the water no longer falls together, and it appears white.

When the particle is organized, the light is uniformly bent, so the image is not very distorted and it appears transparent. However, when there are many transparent particles, a small change in the angle of incidence can cause a large change in both the position and the angle of the resultant light.