Stains are usually one of two varieties, oil-based or water-based. Oil-based stains come from substances such as oil or grease. Other liquids, such as fruit juice and coffee, create water-based stains.
Stains are caused by the physical or chemical reaction between two materials. The staining substance gets trapped in the fibers or pores of a surface. Some staining substances create a chemical reaction with the base. In general, heat causes staining substances to bond with the underlying material. As such, heat drying and ironing typically set stains, making them almost impossible to remove.
Removal of the stain depends on the base. If the stain is oil-based, the first step in removal is to blot up the excess with paper towels or talcum powder. Dish detergent is one agent for removing oily stains, as is straight laundry soap. Hot water is necessary for removing these types of stains as well. If the stain is water-based, agents for removal include vinegar, lemon juice and hydrogen peroxide. A paste of peroxide and salt is especially useful in removing blood stains. Hot water also helps remove juice or coffee stains, though it sets blood. Complex substances such as ink, paint and lipstick often react both as a water-based and oil-based stain. Therefore, they require both types of removal.