Q: I have a cast-iron skillet that I have been using for a few years. It has brown, rust-colored stains that don’t come off, no matter what I do. I’ve tried kosher salt and a small chain, soap, a ...

If you’re bedeviled by rust stains in your bathroom, be thankful you don’t live on Mars, because the entire surface of the planet is covered in it. Rust is a compound known as ferric oxide or iron ...