When spotting with bleaches, keep in mind that bleaching is a process that changes the color of a substance to a colorless state through a chemical reaction. This means that the stains or dyes are not necessarily removed from fabrics, they are merely made invisible by a chemical change. The chemical reactions involved in bleaching are oxidation or reduction. Therefore, there are two categories of bleaches: oxidizing and reducing.
Oxidizing bleaches make stains colorless by adding oxygen to stains. They are most effective on organic stains such as perspiration, urine, and most beverages. Oxidizing bleaches include sodium perborate, hydrogen peroxide, and sodium hypochlorite.
Reducing bleaches make stains colorless by taking oxygen from stains. They are most effective on dyes. Reducing bleaches include sodium bisulfite, sodium hydrosulfite, and titanium stripper.
Although spot bleaching may be the only way to make a stain disappear, bleaching is not always possible. Fabric damage and color loss may occur depending on fabrics and dyes. Therefore, we stress the importance of testing prior to using a bleach to prevent disastrous results.
For more information on bleaches, see TABS No. 397 - Bleach Causes Fabric Damage, Shirt Laundry Procedures, No. 32 - Facts About Hypochlorite Bleaches, and Industry Focus: Use of Bleaches in Stain Removal, and Stain Removal 101, a five-part Technical Operating Information (TOI) series.