18/10 stainless steel is a common and trusted material used extensively in modern kitchens for flatware and cookware. This alloy is valued for its superior performance, including resistance to rust and durability over many years. The designation “18/10” refers to its specific chemical composition, which provides durability and sheen for food contact surfaces. Although concerns about toxicity arise from the metals within the alloy, health organizations generally agree that 18/10 stainless steel is safe for preparing and storing food under normal conditions.
The Chemical Makeup of 18/10 Stainless Steel
The numerical designation “18/10” defines the precise concentration of two alloying elements added to the base iron. This grade contains 18% chromium and 10% nickel, with the remainder consisting primarily of iron and trace amounts of carbon and manganese. This composition is why the material is often referred to as Type 304 stainless steel, a global standard for high-quality food-grade applications.
The 18% chromium content provides the material’s resistance to corrosion. When exposed to oxygen, chromium instantly forms an ultra-thin, invisible layer of chromium oxide on the surface, known as the passive layer. This protective layer self-heals if scratched, preventing the underlying iron from reacting with oxygen and forming rust.
The 10% nickel content acts as a stabilizer that enhances the alloy’s structure. Nickel strengthens the metal, improving its resistance to pitting and general wear. This addition also contributes to the material’s lustrous appearance and helps maintain its integrity even with repeated exposure to high temperatures and various foods.
Addressing Concerns About Metal Release
Concerns about stainless steel safety often center on metal leaching—the release of trace amounts of nickel and chromium into food during cooking. While this occurs, particularly when cooking highly acidic foods like tomato sauce or vinegar for extended periods, the quantities released are very small. Studies show these metal levels are far below the established safety limits set by international health organizations.
For instance, one study found that after ten sequential cooking cycles in tomato sauce, the average amount of nickel released was approximately 88 micrograms and chromium was 86 micrograms per serving. The human body has a tolerable daily intake for nickel around 1,000 micrograms, which puts the amount leached from a single meal into perspective. Furthermore, the leaching effect is highest with brand-new cookware and decreases significantly after the first few uses as the passive oxide layer stabilizes.
The type of chromium released is important, as different forms of the element have vastly different health profiles. The metal in stainless steel is metallic, and any trace amounts that leach into food are in the form of trivalent chromium (Cr III). Trivalent chromium is considered an essential trace nutrient required for carbohydrate and fat metabolism.
The toxic form, hexavalent chromium (Cr VI), is a known carcinogen, but it is not released under normal cooking conditions. Creating Cr VI from stainless steel requires a strong oxidizing agent or extreme industrial processes, which do not occur in a home kitchen. While a small percentage of the population has a sensitivity to nickel, the trace amounts released are usually insufficient to cause a systemic allergic reaction.
Best Practices for Safe Use and Maintenance
Maintaining the integrity of the 18/10 stainless steel surface minimizes potential metal release and ensures longevity. The protective chromium oxide layer can be compromised by physical damage, so avoid using abrasive cleaning tools like steel wool or harsh scouring pads. Instead, remove stuck-on food by soaking the item in warm, soapy water before gently scrubbing with a soft cloth or sponge.
It is advisable to avoid using the cookware for prolonged storage of highly acidic or salty foods, as this can increase the rate of leaching and potentially cause pitting in the metal. If the cookware develops noticeable pitting or significant scratches, the item should be replaced, as this indicates the protective layer is constantly challenged. A good practice for new cookware is to “season” it before the first use by boiling water for a few minutes, which helps stabilize the surface and clean off any residual manufacturing oils.
Always allow the cookware to cool completely before washing to prevent warping, and dry it immediately after cleaning to avoid water spots and mineral deposits. Using only wooden or silicone utensils while cooking helps prevent scratching the surface, which maintains the integrity of the protective layer. These simple maintenance habits ensure the 18/10 stainless steel remains a non-reactive and durable tool in the kitchen.