Have you ever looked at shaving cream after it comes out of the can? This is lather. The foam is almost structural in its density and strength. Kids love playing with it because it is very nearly moldable, like a very lightweight foamed plastic. It is nothing like the lather than you get from soap. So where does this kind of foam come from?
You can read all about the aerosol can in How Aerosol Cans Work. But neither the can nor the delivery system is the reason why this foam is so cool. The foam is made by the chemicals in the can.
According to How Products Are Made, all shaving creams contain the same basic ingredients:
A standard recipe contains approximately 8.2 percent stearic acid, 3.7 percent triethanolamine, 5 percent lanolin, 2 percent glycerin, 6 percent polyoxyethylene sorbitan monostearate, and 79.6 percent water. Two major ingredients in this formula are common in many of today's preparations. Stearic acid is one of the main ingredients in soap making, and triethanolamine is a surfactant, or surface-acting agent, which does the job of soap, albeit much better. While one end of a surfactant molecule attracts dirt and grease, the other end attracts water. Lanolin and polyoxyethylene sorbitan monostearate are both emulsifiers which hold water to the skin, while glycerin, a solvent and an emollient, renders skin softer and more supple.
The combination of the glycerine, lanoline, Stearic acid and triethanolamine gives shaving cream its extra-creamy and dense lather. That combined with the propellant (often butane or propane) expands and instantly evaporates when it leaves the can, filling the foam with its millions of bubbles.
Shaving is obviously a big deal, and billions of people do it every morning. To learn lots more about shaving, check out the links on the next page.