Laundry detergent, or washing powder, is a type of detergent (cleaning agent) that is added for cleaning laundry. While detergent is still sold in powdered form, liquid detergents have been taking major market shares in many countries since their introduction in the 1950s
Laundry detergent pods have also been sold in the United States since 2012 when they were introduced by Procter & Gamble as Tide Pods. Earlier instances of laundry detergent pods include Salvo tablets sold in the 1960s and 1970s.
From ancient times, chemical additives were used to facilitate the mechanical washing of clothing with water. The Italians used a mix of sulfur and water with charcoal to clean cloth. Egyptians added ashes and silicates to soften water. Soaps were the first detergents. The detergent effects of certain synthetic surfactants were noted in Germany in 1917, in response to shortages of soap during World War I. In the 1930s, commercially viable routes to fatty alcohols were developed, and these new materials were converted to their sulfate esters, key ingredients in the commercially important German brand FEWA, produced by BASF, and Dreft, the U.S. brand produced by Procter and Gamble. Such detergents were mainly used in industry until after World War II. By then, new developments and the later conversion of aviation fuel plants to produce tetrapropylene, used in household detergents, caused a fast growth of domestic use in the late 1940s.
Washing laundry involves removing mixed soils from fiber surfaces. From a chemical viewpoint, soils can be grouped into:
Water-soluble soils such as sugars, inorganic salts, urea, and perspiration.
Solid particulate soils such as rust, metal oxides, soot (carbon black), carbonates, silicates, and humus.
Hydrophobic soils such as animal fats, vegetable oils, sebum, mineral oil, and grease.
Proteins such as blood, grass, egg, milk, (starch), and keratin from the skin. These require enzymes, heat or alkali to hydrolyze and denature them into smaller parts before they can be removed by the surfactants.
Bleachable stains such as wine, coffee, tea, fruit juices, and vegetable stains. Bleaching is an oxidation reaction that turns the colored substance into a colorless one, which either stays on the fabric or maybe easier to wash out.
Soils difficult to remove are pigments and dyes, fats, resins, tar, waxes, and denatured protein.