Gillette never launches a new razor without having its successor in the pipeline. So with SensorExcel about to be launched, Terry and his colleagues had to top their own best efforts. SensorExcel and its predecessor, Sensor, were the most popular razors in Gillette's history, but they retained a twin-blade configuration that the company had been using for twenty years. Gillette scientists wondered if something more dramatic might be possible.

"We knew that if you had more blades you'd be able to cut more hair," Terry said. "But we found that what you gained in efficiency you lost in comfort, irritating the skin too much in exchange for the closeness. People wouldn't pay for that - too many nicks and cuts. Then, one day in 1991, we were in the lab and Bernie Gilder said, 'What if we lowered the trailing blade?'"

Gilder was no whiz kid. He had been with Gillette for decades and his insight was the product of what Terry calls "tacit knowledge" - knowledge that you acquire only after spending a lonf time in those linoleum-floored shaving labs. Still, in the incrementalist world of shaving technology, his idea counted as a bona fide apple-on-the-head brainstorm.

Every shaving engineer knew why two razor blades were better than one. As a razor moves it makes the skin bulge, forcing hairs up and out of their follicles. The first blade catches the hair, pulls it up, and slices through it, after which the hair starts to retract. Before it can retract fully though, the second blade catches it and cuts it below where the first bladed did. A third blade would do the same, but it would tend to get too close. Gilder's insight was that by setting up each of the three blades at a different angle - a difference invisible to the naked eye - the third blade would be able to get closer to the skin without tearing at it.

The new three-blade model was code named Manx (the coat of arms of the Isle of Man has three legs), and when Miles Yeoman ran it through his reflex stereo machine he found that it removed forty per cent more hair than Gillette's best product, the still brand new Sensor Excel. Then the robust friction device proved that the razor was also exerting less drag on the face. In other words, Manx seemes to offer a shave that was both closer and more comfortable, which is the Holy Grail as far as shaving techies are concerned. In its first "out-plant" shaving test, Manx was a huge hit with consumers, too. "So we knew we had a winner," Terry says, a wide grin creasing his face.

Both Gillete's corporate culture and its marketplace strategy, though, are based on technological supremacy in shaving, and from this perspective, Manx has had one major shortcoming: its blades, like those of Sensor were made out of the same material - steel coated with a platinum-chromium alloy - that Gillette had been using since the late nineteen sixties. Rolling out a new razor with technology that was almost thirt years old hardly accorded with the company's revived ethic of innovation. So, in late 1993, Gillette's CEO, Alfred Zeien laid down the edict; Mach 3 would deploy an entirely new blade technology. It was up to the scientists, of course, to figure out what that might mean.

The problem the Gillette scientists faced was that the thinner the edge is, the more easily it wil cut hair, but a thin edge is also more fragile, so you get to the point where running into a hair will actually break the edge off. Coat the blade with a super-hard substance, though, and you can make it sharper.

The scientists had a great candidate - a substance called diamond-like carbon, or DLC. But DLC wouldn't bond with steel, so when you tried to coat a blade with it the stuff simply slipped off. The metallurgists in Boston realised that the trick was to put between DLC and the steel something that both substances could bond to. Knowing that they had to find that something in time to meet the approaching deadline, they worked weekends and nights, testing every possible candidate until they arrived at a metal called niobium, which bonded nicely with both DLC and steel. Manx now had blades that were two or three times as hard as steel and that cut hair better than anything else in the world.