What is an “Invisible Stain”?
As unlikely as it sounds, there are a group of stains known as “Invisible Stains”.
Most of them are caused by either; food, oily substances, or beverages. Although quite visible while wet, once dried it becomes invisible. Hence the name, Invisible Stain! Later on, with exposure to heat or time, a yellow or brown colored stain will appear. This is caused by the oxidation or caramelization of the sugar in the substance that has stained your clothes. It is the same process that makes an apple turn brown after being exposed to air.
Oil stains can be particularly challenging. Dry cleaning can successfully remove most oil stains, unless they are left to oxidize. Once oxidized, they turn yellow or brown, and become much harder to remove. This type of stain can be distinguished by the irregular “cross pattern” the oil makes along the edge of the stain as it follows the fabrics fibers.
If you know about an invisible stain on your clothes, be sure to point it out to the cleaner when sending in your garment. The cleaner will need to treat these stains prior to cleaning, since the heat of drying or pressing may set the stain in.