Question

why do a soap forms more bubble as compare to shampoo?​

Answer 1

Soap molecules have two ends — one end likes to stick to water, and the other end is repelled by water. The bubbles you see when you wash your hands are caused by this property of the soap molecules. ... So the bubbles form spheres because this uses the least amount of soap (and thus energy) to form the bubble.

Answer 2

Simple home made soap is the product of a mixture of oils which contain fatty acids, and lye (Sodium Hydroxide or NaOH), as opposed to detergents and other constituents found in mass produced soaps. The reaction which takes place is referred to as saponification, and the product, soap, is a salt. Because the oils contain multiple fatty acids, the salt produced is a mixture of multiple types of salt, like sodium palmate, or sodium laurate.

The soap recipe usually involves blending oils together, like Olive oil and Palm Oil (Palmolive!), to react with the lye yielding soap. Which oils are used determine the relative quantities of the different salts.

Most oils such as Palm Oil are composed of more than one type of fatty acid. Yes, Palm Oil contains palmitic fatty acid, but it contains others as well. The most important fatty acids present in soap oils are:

Lauric

Myristic

Palmitic

Stearic

Ricinoleic (Castor Oil is the only real player here)

0leic

Linoleic

Linolenic

Certain fatty acids aid in developing suds/bubbles/lather. The big hitter here is Lauric acid. Myristic acid also gives a stable (long lasting) fluffy lather in soap. Soapmakers have found that some Ricinoleic acid is very helpful in maintaining a good sudsy lather, so we add 5–10% Castor oil into the recipe.

The water you use with the soap also plays a big role. Hard water rich in Calcium and magnesium ruins soap effectiveness and lather or suds. This is why you want a water softener if you can afford one in your home (assuming you have hard water in the first place which most people do).

If you think about it, seawater then would be a horrible water to bathe with (for lots of reasons besides ruining the effectiveness of your soap). So the Navy used to use Coconut Oil based soap when sailors bathed with seawater because coconut oil based soaps have so much Lauric and Myristic acid in it that they will still suds-up, even in seawater.

There are downsides to everything unfortunately, and 100% coconut oil soap might suds up great, but it produces a bar of soap that is hard as a rock to the point of being brittle! It is also very drying and harsh on your skin. So for suds and bubbles most soapmakers use only a fraction of coconut oil in their recipes, up to about 20%.