Sudan Black is one of the best processes for developing latent prints on smooth or rough, nonporous surfaces contaminated with greasy or sticky substances. It works best on glass, metal or plastic materials and can be used on waxy surfaces, such as candles or wax-paper milk cartons. Sudan Black stains the fatty components of sebaceous secretions from the skin. Try this process on the inside of those latex gloves left behind at the scene of a burglary. Sudan Black is easy-to-use, inexpensive and nontoxic.