Protein foams contain natural proteins as the foaming agents. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. Foaming or rinsing is not necessary. These compounds can act as surfactants or foaming agents. Because air is not hydrophilic, detergents are also foaming agents to varying degrees. These products might also have surfactants to improve emulsification and spreading in the foaming medium. The Marangoni effect depends on the liquid that is foaming being impure. Sulfates are also responsible for the foaming effect of shampoos. Insufficient hardness can lead to corrosion and water foaming. Boiler water is treated to prevent scaling, corrosion, foaming, and priming. Supercritical carbon dioxide is used in the foaming of polymers. Eggs function as emulsifiers, foaming agents, and tenderizers in the dough. Decreased bubble coalescence leads to smaller bubble sizes and greater foaming ability in water. Some tenders carry also foaming agents, and extinguishing powders or gases. The foaming water creates ever growing and impressive waterfalls.