Stainless steel soap is a solid, typically oval-shaped piece of stainless steel used in the kitchen to counteract strong scents that linger on hands after cooking. It is not a traditional cleansing product; unlike a bar of soap, it does not lather, contain surfactants, or dissolve with use. The item’s function is to neutralize persistent odors through a chemical process rather than washing them away.
Odors Stainless Steel Soap Targets
The bar is designed to neutralize odors arising from specific chemical compounds that transfer from food to the skin. These unpleasant smells primarily result from volatile sulfur compounds found in ingredients like garlic, onions, leeks, and chives. When these allium vegetables are cut, enzymes release sulfur-containing molecules, which cause the strong, persistent aroma. The bar is also effective against the fishy scent remaining after handling seafood, which is caused by nitrogen-containing amine compounds. Both sulfur and amine molecules adhere strongly to the skin and are often difficult to remove with plain soap and water.
The Scientific Mechanism of Odor Removal
The accepted explanation for the bar’s deodorizing effect centers on the unique chemistry of stainless steel, which is an alloy containing iron and at least 10.5% chromium. The surface of the steel is naturally protected by a thin, invisible layer of chromium oxide, known as the passivation layer. This layer and the underlying metal ions are believed to interact with the odor-causing molecules. When the bar is rubbed under running water, the water acts as a necessary catalyst for the reaction. The water helps dissolve the sulfur molecules, such as the mercaptans from garlic, which then form ions. The positive charges of the metal ions on the steel surface attract and chemically bind to the negatively charged sulfur ions, transferring them from the skin.
This binding process essentially traps the odor molecules on the steel, a phenomenon sometimes described as an oxidation or transfer reaction. By binding the sulfur and amine compounds, the metal neutralizes their ionic charge and prevents them from volatilizing and reaching the nose. Common grades of stainless steel, such as 304 or 316, are used to ensure the material’s durability and corrosion resistance during this process. However, the precise chemical mechanism remains a subject of debate among scientists, as rigorous studies are scarce. Some researchers suggest that the perceived benefit may be partially due to the mechanical action of rubbing the hands under running water, which physically removes some of the odor-causing compounds. Others suggest that a psychological effect, or placebo, may also contribute to the reported effectiveness.
Best Practices for Using Stainless Steel Soap
For the stainless steel soap to work effectively, it must be used in conjunction with running water. The water flow is necessary to facilitate the chemical transfer and act as a carrier to rinse away the odor molecules that have bound to the metal. The temperature of the water is generally not considered a factor. Begin by holding the bar and rubbing it vigorously between your hands under the stream of water for approximately 30 to 60 seconds. The friction helps ensure maximum contact between the steel surface and the odor molecules on the skin.
After use, the bar should be rinsed clean of any transferred molecules and allowed to air dry. Since the metal neutralizes odors rather than absorbing them, the stainless steel bar does not wear out and can be used indefinitely. Avoid using harsh chemical cleaners or abrasive scrubbers, as this can damage the protective chromium oxide surface.