Keeping clean has been a preoccupation of humans for millennia (well, some humans, anyway; there were those unfortunate few centuries in Europe when it wasn’t high on anyone’s list of priorities). Since water is essential to life, people settled near water, and soon learned that it could clean things, too, like clothes (once clothes were invented, that is). By 2800 B.C., the ancient Babylonians had learned to boil fats with ashes, which is how you make soap (though we don’t know exactly what they did with it)…and that’s where cleaning technology stopped for the next couple of millennia. From skin to clothes, you cleaned it with soap, if you cleaned it at all.
This century, however, has seen a revolutionary change in the way people clean things, especially clothes: the development of detergents. And the granddaddy of them all, Tide, just marked the 50th anniversary of its introduction.
Soap has a straightforward definition (although it’s not one they push in advertising): it’s a natural cleansing agent produced by the reaction of an alkali with animal fat or vegetable oil. Detergent’s definition is equally straightforward: it’s a synthetic chemical that acts as a soap. The key is “synthetic.” Until this century, very few synthesized chemicals existed, and the widespread synthesizing of materials out of hydrocarbons (which is what detergents are mostly made out of) didn’t really take off until the Second World War–which is when Tide was invented.
The need for something better than soap was apparent to anyone who ever washed clothes using laundry detergent’s predecessor, soap flakes. Despite its 2,000-plus year history, soap had disadvantages when used to wash clothes, chief among them the way it reacts to hard water: it causes the mineral salts in the water to form an insoluble substance which goes by the highly technical name of “scum.” This scum doesn’t rinse away, so it produces visible deposits on clothes and makes fabrics feel stiff. Even washing in soft water doesn’t always solve the problem of scum, because some hardness minerals are introduced into the water by the very soil the soap is intended to remove from the clothes. And soap molecules don’t lend themselves to being adapted to the huge variety of fibers and washing conditions used on clothes today.
The Procter & Gamble company made soap–its Ivory Snow soap flakes were one of the most popular brands for washing clothes earlier this century–but it knew soap’s disadvantages and, at the turn of the century, began searching for a better way. By the 1920s, P&G chemists had figured out a way to create chemicals with special two-part molecules, one end of which was attracted to water and the other end of which was attracted to grease and dirt. Using this chemical in water could loosen grime in clothes, holding it suspended until it could be washed away. They called these new molecules “synthetic surface-active agents”–synthetic “surfactants” for short.
In 1933, P&G introduced the first detergent that used these synthetic surfactants. Called Dreft, it eliminated the problems with soap–but it was only suitable for lightly soiled clothes. The next step was to develop a heavy-duty detergent. It took 10 more years to discover the answer: a mixture of surfactants and other special chemical compounds called “builders,” which help surfactants penetrate clothes fibers more deeply, so they can get at heavier soil. Tide, the result of an estimated 200,000 man-hours of work, was born.
The Second World War intervened in Tide’s introduction, but once the War was over, Tide was tested in six markets in October, 1946, already sporting its trademark yellow-and-orange bull’s-eye box (designed to immediately attract attention to the new product). It was a huge success–demand outstripped supply so rapidly that P&G wasn’t able to complete the conversion of its soap-making factories (about 60 percent of which were rendered obsolete by Tide) fast enough to meet it, and it wasn’t until May, 1949, when the last state–Alaska–finally got supplies.
Detergents have gone through changes since then. Today’s detergents still include synthetic surfactants, which in addition to helping lift soil from clothes, as noted above, improve the wetting ability of water by reducing its surface tension (so it can more easily slip into the small spaces between the threads in cloth, for example) but they come in more than one flavor, determined by their electrical charge properties in water:
“Anionic” surfactants, the most widely used, are negatively charged on the end attracted to water, which means they attract the positively charged molecules (calcium and magnesium) that cause hardness and tend to deactivate them. They’re really good at removing oily soil and clay, but their reaction with hardness molecules tends to deactivate them, too, so they need help from other ingredients.
“Nonionic” surfactants don’t carry any charge at all, so they aren’t deactivated by water hardness–but then, neither do they deactivate it. They’re good on oily soils as well, and are frequently used in low-sudsing detergents and liquid detergents. They’re often mixed with anionic surfactants to better deal with hard water.
“Cationic” surfactants carry a positive charge in water, so they don’t react with hardness molecules either. They’re often used in fabric softeners or fabric-conditioning detergents; their positive charge reduces static electricity.
Detergents still include builders, which also come in various flavors: sequestering builders, which grab on to water hardness molecules and keep them in solution (this is what phosphates were used for before they were removed from detergents), precipitating builders, which causes water hardness minerals to precipitate out so they can be washed away, and ion exchange bulders, which are insoluble materials that also tie up calcium hardness minerals.
Other ingredients in detergents today include antiredeposition agents, which prevent loosened soil from reattaching themselves to the cleaned fabrics; corrosion inhibitors, designed to prevent washer machine parts from corroding; and fluorescent whitening agents, which adhere to fabrics rather like dyes, absorb ultraviolet energy and convert it to visible blue light, making fabrics (especially whites) appear brighter.
Detergents often also include processing aids, which include everything from chemicals to make powders flow more smoothly to alcohols to adjust the viscosity of liquid detergents (and keep them from freezing in cold storage); colorants, which either make the product more attractive enhance whites by adding a blue/white color; fragrances, which cover the chemical smell of detergents and make fabrics smell nice after they’re washed.
Some of the newest cleaning agents in detergents include all-fabric bleach, for stain and soil removal; enzymes, which aid in breaking down complex grime, especially protein-based substances like grass and blood; suds control agents, which can either make suds last longer (for light-duty detergents) or inhibit them (for heavier-duty products); and fabric softening agents (the aforementioned cationic surfactants, for instance).
One ingredient you generally won’t see any more is phosphate. Phosphate was the original builder: it contains the element phosphorus, an essential nutrient to water plants and algae. Increasing the level of phosphorus in the water leads to lakes choked with weeds and algae. As a result, phosphates are just about gone from detergents.
Detergents may not rank up there with trips to the moon or the development of the atomic bomb as one of the great scientific stories of the 20th century in most people’s minds–but maybe it should.
After all, if cleanliness is next to godliness, then detergents are truly divine.
