But does it rot your shorts?: Who invented washing powder? How does it work? Why are the manufacturers at war?

SOAP WARS have broken out between two of the biggest manufacturers of washing powder over the multi-billion-pound business of getting clothes 'whiter than white'.

Procter and Gamble, makers of Ariel and Bold, claimed that Persil Power, made by Unilever, contains a substance that can 'rot' boxer shorts and briefs. Unilever, which spent pounds 100m over five years developing Persil Power, vehemently denied the accusation, taking out full-page newspaper advertisements to get its message across.

At the centre of the dispute is a patented 'accelerator' which Unilever says helps the other ingredients to work faster, leading to shorter washes and less damage to clothes. Procter and Gamble, however, has produced photographs of underwear that allegedly became frayed when washed in Persil Power because the manganese compound in the accelerator degraded the fabric.

Q Who invented washing powder and what did we use before?

A Before powders we used bars of soap and a lot of elbow grease. Soap has been around for centuries. Pliny the Elder wrote in the 1st century AD that the Phoenicians prepared it from goat's tallow and wood ash in 600BC. The Celts had a recipe based on animal fat and plant ashes and gave it the name saipo, from which the modern word derives. Soap production continued as a cottage industry through the Middle Ages to Napoleonic times by which time it had become heavily taxed. It was the Victorians, most notably the Lever brothers at Port Sunlight, Merseyside, who made soap on a larger industrial scale. They refined the manufacturing process to produce soap flakes and soap powder to help it dissolve more easily in water.

Q What are the basic ingredients?

A Soap has long since given way to artificial detergents as the main ingredients of washing powders. They do the primary job of helping water to penetrate the clothing and so wash away dirt and stains. Other ingredients include phosphates, a 'builder' as they say in the trade, which combats the natural hardness of water. The main job of builders is to tie up the natural salts found in hard water to stop them interfering with the action of the detergents. Then there are optical brighteners to make white clothes look less yellow. These compounds reflect blue light, which is why white shirts look so luminous in the ultra-violet light of a disco. Other ingredients include bleaches for removing difficult stains, and enzymes and catalysts for speeding up stain-removing reactions at low-temperature washes. Perfume additives make it all smell nice.

Q How many of the constituent parts vary from powder to powder?

A It's difficult to say, because companies jealously guard their own 'unique' formulae. Some powders appear to be merely revisionist recipes which hark back to simpler times. New powders designed for 'colours', for instance, are really the same as other washing powders but with less bleach. The big companies say they spend large amounts of money researching washing powders designed for specific markets. The British apparently wash their clothes quite differently from Americans, who have bigger machines, use more water and pour more bleaching agents over their smalls.

Q Where does the raw material come from?

Petroleum oil is a principal material for detergents, brighteners and perfumes. Vegetable oils, from palms and olives, are used for some detergents and come from southern Europe, Indonesia, Africa and the Philippines. Phosphates come from calcium phosphate rock, mined in places such as Morocco and the US. Borax rock mined in Arizona and Turkey is a principal source of sodium perborate, a bleaching agent. Silica rock mined in Brazil and Italy is made into zeolite, a water softener. Enzymes are made by fermenting microbes, mainly by Danish biotechnology companies. Oh, and the carboard box comes from Canadian or Scandinavian wood pulp.

Q How is washing powder made?

A Imagine baking a cake on a large scale. Correct amounts of the ingredients are mixed together following a recipe and cooked for the right time at the right temperature. The recipe for the detergent is called a 'formulation' and is a trade secret. The fundamental chemical reaction that leads to the formation of a detergent is saponification - mixing fat or oil with an alkaline substance. (It is said the first soaps could have been made inadvertently by Stone Age man roasting animals over a fire - dripping fat could have reacted with alkaline ashes to produce a primitive soap.) Phosphates, silicates and optical brighteners are added to the liquid slurry of detergent before it is pumped under high pressure into a spray-drying tower where hot air turns the liquid droplets into a powder. Further ingredients, such as enzymes, dyes and bleaches are then added.

Q How do washing powders work?

A The workhorse of the powder is the detergent, a 'surfactant' or surface-active agent which helps water to penetrate clothing. Water can be compared to custard with a skin on top. Surfactants work by getting rid of the skin. They are molecules with a water-loving end, which sticks into the water, and a water-hating end, which sticks out - rather like a fishing float. These molecules help water to get close to dirt, surrounding it, softening it and helping the warm water to wash it away. Stains made by such things as tea, coffee and wine are difficult to remove by detergents alone, so bleaches are added which chemically break down the colours of the stain. Many of the other ingredients, are there to ensure the detergents work properly.

Q What is an accelerator?

A Since the 1980s there has been a general trend for people to wash clothes at lower temperatures. We like this for several reasons: it's gentler on clothes, especially brightly coloured modern synthetics, and gentler on the pocket because less hot water means lower fuel bills. The trouble is, as any school pupil will tell you, reactions tend to be slower at lower temperatures, unless you add magic ingredients known as catalysts which speed up reactions significantly. An 'accelerator' such as manganese is, more or less, merely a catalyst which allows the bleach to work at lower temperatures - say 40C instead of the usual 60C.

Q So are enzymes accelerators?

A Sort of. Enzymes are biological catalysts because they are designed by living organisms to speed up chemical reactions in the body. The first enzyme for use in washing powders was introduced in the Sixties. The latest is a lipase, which dissolves fats at low temperatures and again serves the function of enabling people to wash badly soiled clothes in cool water. One of the problems with enzymes, however, is that, because they resemble naturally occurring substances, some people can develop allergic reactions to them. It is for this reason that companies have re-introduced the 'non-biological' washing powder.

Q Are washing powders really improved continuously?

A There do seem to be genuine breakthroughs in the evolution of washing powders. Optical brighteners, enzymes and the trend to produce powder for low-temperature washes are probably the best examples. There has also been a trend in recent years to make 'micro' powders, which are more concentrated, enabling manufacturers to claim a 'greener' image by using less packaging. But there is a lot of hype because companies realise that, for many people, the reasons for choosing one brand over another is quite arbitrary. They need to 'improve' or at least change the look of their products continually to make it appear that their products are state-of-the-art technology. But the fact that companies have sometimes had to revert to earlier recipes suggests that washing powder evolution is not always straightforward and much of it is designed for marketing purposes.

Q How much do the British spend?

A Britain consumes nearly half a million tons of washing powder a year - about 7,000 kilos per head of the population - equivalent to annual sales of about pounds 1bn. The Germans and French use a little more than we do. The Spanish appear to use more washing powder than any other European nation - nearly twice as much at the British. Turkey has the lowest per capita consumption in Europe, at about 2,000 kilos per head per year.

This is how our boxer shorts came out

THESE are the Marks & Spencer boxer shorts at the centre of a dispute between the soap powder makers Procter & Gamble and Unilever. P&G says it washed a pair of shorts 16 times using its own Ariel Ultra and an identical pair with the opposition's Persil Power - alleging the Persil Power wash reduced the undies to a tattered state. But when we ran the identical test, the result merely gave credence to the cynics who believe there is not much difference between such products. If anything, the Persil pair (middle) fared best. The shorts washed with Ariel (bottom) showed slight shrinkage and loss of colour, but neither pair looked much worse than those bought straight from the shop (top).

(Photographs omitted)