How much do you know about that nice coating of acid on your skin? (Yes, I'm serious.) As it turns out, the outer layers of skin are about as acidic as a bowl of crushed tomatoes! The acid is produced when enzymes break down fat-like molecules in skin cells, called phospholipids, into smaller acid-tipped fat molecules called fatty acids. Add to that normal perspiration, made up of mostly fat and fatty acids, and these mild chemicals mixed with warmth and air exposure can corrode metals like 14-karat gold, sterling silver, and this aluminum keyboard.
Want to learn some beauty ingredients that can make this worse and where these smudges actually come from? Find out while we get all Mr. Wizard in here.
On top of the acid in your skin and perspiration, certain products have higher acid content than others. If your lotions (or other cosmetics applied with your hands) include zinc oxide, titanium dioxide, ferric oxide, or calamine, this can add more acid and even tarnish your jewelry. When these hard compounds come in contact with metal, they rub off tiny — too tiny to spot — particles of metal, which appear as black dust. When you add your existing acid content to that metallic dust and other bitty particles on an absorbent surface like the keyboard, just say hello to the black smudges that can result.