The ancient Greeks started it, and in London's East End, soap- making is still going strong. By Ros Byam Shaw
AN EAST-END soap factory; it sounds Dickensian, the kind of place where hollow-cheeked children might be found stirring vats of stinking tallow. Soap is still made, as it always has been, from the basic ingredients of fat, ashes (alkali) and water. This horrible amalgam was discovered by the ancient Greeks who found that their washing came out whiter on the days when animals were slaughtered on the hill above the river. The fat and blood from the sacrificial beasts ran down into the water where it mixed with natural salts from the soil to make lather.

Woodspirits UK make soap by hand in the traditional way but their premises on a modern industrial estate are scented and airy and more like a sweet shop than a factory.

The soap they make comes in a myriad of edible hues and a range of equally delectable smells; lined up on wooden racks, some look like fudge, some like solidified gooseberry fool or chocolate custard or honey and yoghurt. Some soaps are marbled, some striped. Some contain flakes of oatmeal, or dried lavender. "Lapis" is flecked with real gold leaf; "Phome" has a top layer of tapioca - a brilliant reinvention of a school-dinner horror. Sliced into square-edged bars, this is soap with a tactile, rough-hewn quality.

Presiding over this emporium of natural ingredients are father and daughter Nicola and Eddie Clark who between them can turn out as many as 5,000 handmade bars of soap a week. In her office, Nicola recalls the early days of the business. "I made friends with an American called Barbara Bobo. She was working as a herbalist in Ohio - a bit of a witch, the sort of person you went to for a brew. Then she started making soap, mixing it on her stove with a spoon and using her knowledge of herbs. After university, I went out to help her and she came up with the idea that I should make and sell soaps to her recipes in England."

After a rocky first six months, largely financed by Eddie, the orders started to roll in. Nowadays, their scented slabs are found in some of the smartest shops in town; they make bespoke soaps for Margaret Howell and Egg, while stockists for their own range include Liberty, Selfridges, Designers Guild and Fortnum's. Mail order is growing.

So where is the fat and where are the ashes? Rough-hewn it may be, but the ingredients of this handmade soap have come a long way since the days of animal sacrifice. In fact they are distinctly refined and, in many cases, good enough to eat.

Rather than using animal fats or petroleum-derived oils, Woodspirits use more expensive vegetable oils, principally food-grade coconut and olive oils. Any kind of fat can be used to make soap. Eddie Clark says that when soap was still a cottage industry, the soap-maker would call on households to collect unwanted cooking fat. "Tallow, which is rendered beef fat, makes perfectly decent soap," says Nicola. "And its use is a form of recycling which is good. Some commercial manufacturers even collect old chip fat."

Here, the fat comes as pure white slabs of coconut oil and in pretty tins of pale golden olive oil. To make the soap, these are heated and mixed in a huge honey vat. When full, this giant tin can hold 260 litres of oil which translate into 1,800 bars of soap. Mounted above the honey vat is a smaller metal drum containing the modern equivalent of alkali ashes, pellets of sodium hydroxide mixed with water. Better known as caustic soda, this is the corrosive stuff that we put down our drains. But, when mixed with fat at the correct temperature, it undergoes a transformation which neutralises its harmful effects. This is the chemical process known as saponification.

To watch Eddie Clark open the spigot in the upper vat and allow the liquid sodium hydroxide trickle in a clear, steady stream into the warm oils while stirring it in with an enormous wooden paddle, is to see alchemy at work. The thin translucent liquid thickens and clouds, turning into runny soap before your eyes. As oil and alkali combine, glycerine is released from the oils and rises to the surface. Most commercial soap manufacturers skim off the glycerine, a valuable moisturiser used in expensive face creams. Here, however, it is stirred back into the mix.

Once the initial stages of this chemical reaction are complete, scents and natural pigments can be added. Today they are making a soap called "Swedish Sauna" which contains essential oils of birch, wintergreen, basil, cinnamon, marjoram and rose geranium. Deliciously fragrant, the creamy contents of the vat are poured into the moulds. After a night in the mould house, the soap has set hard enough to be cut. Three weeks later, it's ready for use.

Nicola particularly enjoys making up new samples for customers: "We have about 40 essential oils and resins, and 27 different soaps, but you can always come up with something new. Lime and ginger was a recent one." As for the therapeutic and medicinal properties of the soaps, Nicola says she hasn't been ill once since she started making them.

Woodspirits UK, Unit 42, New Lyndenburg Industrial Estate, New Lyndenburg Street, London SE7 8NE (mail order: 0181-293 4949)