What makes soap foam? | HowStuffWorks
There are many different kinds of soap in the world and most of them have one major thing in common: They can make bubbles. When you amass a bunch of tiny bubbles together, we call it foam or lather.It doesn't matter if you're talking about bar soap, shampoo, dish soap or laundry detergent -- the same thing happens when you mix any of them with air and water.