REMEMBER THOSE TV ads in which a razor traversed the skin of a man's cheek, twin blades the size of aircraft propellers hacking into hairs giant as flax leaves?

No? Well, they did air in 1971 but are probably somewhere on YouTube. The first blade lifted the hair as it cut and the second slashed through it, leaving the hair to slip, beaten and bowed, beneath the surface of a face as smooth and huge as a hot-air balloon. Neat, clean, sleek. So how come we now have three, four and five blades on our razors?

It turns out those ads weren't exactly lying, but they weren't telling the entire truth. They demonstrated a new shaving discovery, "the hysteresis effect", in which the cut hair protrudes temporarily above the skin.

What shaver-makers didn't have so much of a handle on back in the early 1970s were things like "interblade span", "skin bulge", "frictional characteristics" and that must-have: "rinsibility". Kevin Powell can't be blamed for that simplistic ad science moves on, and anyway in 1971 he was three years old. Though he can be blamed for the above shaving jargon and any other in this story. Powell is lab director at Gillette's research centre in Reading, near London, and his PhD in ceramics engineering did lead him to working with jet engines at Rolls Royce and missile guidance at the UK Ministry of Defence before he moved, inevitably, into razors.

Powell, who's one of those chatty, enthusiastic, likeable boffins with an unplaceable southern English accent, says blade-makers did actually know about the interblade effect in 1970s having the right distance between blades reduces skin bulge and so drag but the technology didn't exist. There was too much variation in the production of the blades. And since then they have also solved the problem of close blades clogging up by using narrow blade supports, easing many a man's nightmare about insufficient rinsibility.

But the quest for the perfect razor goes on. And it's all about the customer, Powell insists. The multiple blades, the pivoting head, the glide strip, the battery-powered vibrations to further reduce drag, the trimming blade on the back for sculpting facial hair it's what men said they wanted, he says. Gillette's Mach3 delivered a pretty good shave, he says after spending a reported $US750 million on research and testing yet the chimera of perfection beckoned. The customer wanted more, more, more or so we are told.

Competition is fierce. Why? Because the market for non-disposable razors in this tiny country of two million men is worth about $30 million a year, Dave McLeod, the New Zealand manager of market minnow King of Shaves, told the Sunday Star-Times last year. The separate shaving preparations market is worth about a third of that. In the US the male razor market tops $US2 billion. Gillette claims about 70% of the market here, which is typical. Schick-Wilkinson Sword, now owned by Energizer, the batteries people, is probably its fiercest rival, with others like Super-Max and King of Shaves biting at their spring-loaded heels. Lawsuits frequently fly over intellectual property shavers are some of the most patented consumer products around.

Gillette almost certainly spends the most to maintain its lead. It wouldn't tell us how much but its owner, Proctor & Gamble, whose products range from pet food to Old Spice to CoverGirl makeup to Braun electric shavers, spends $US2 billion a year.

Men are the market lodestone for razors, as we shave four or five times a week compared to women's paltry once or twice. So what else has the male shaver been asking for?

Says Powell: "He was telling us he was looking for further comfort during the stroke, less pulling on his face, greater improvement in safety, so fewer nicks and cuts and less irritation, and he was looking for an improvement in manoeuvring in hard-to-reach places."

Greater comfort came from less bulge, which came from changing that interblade span. In the Mach3, the blades were 1.5mm apart; in Fusion they are just over 1mm.

"What you get when you do that literally we measure the bulges that form on people's skin, kinda fun you can see a 45% reduction in the skin bulge height. That's what translates into them saying, `wow, this is a helluva lot more comfortable, it's an awful lot safer, there's less irritation, there's an awful lot less nicking and cutting'. So the science is critical to quantify what the consumer is telling us, and then to measure that indeed our concepts are delivering against his needs."

His needs. What if his needs don't quite stretch to paying more than $5 for each of the Fusion Phenom cartridges? I tried the Phenom and it gives a damned good shave, but Schick's Quattro probably does a reasonable job, as do the many cheaper three-blade options. But then I can get two months of shaving for $5 out of the safety razor I started using last year. There's a recession on, you know.

Don't underestimate the power of the brand. Brands hold emotional sway over us, says Richard Bourke, of market research company Big Picture. Because grooming is closely tied up with power and status and fashion and attractiveness, many people will pay a premium for such products.

He says there is always "some level of resistance to the latest and greatest", and some will "trade down" if it's just one more blade or some magic ingredient, but that's a functional judgment. If your emotional bond to the brand is strong, there is "price elasticity" that is, we will pay whatever it costs.

And that technology costs all right. Forget the laser-guided 3D prototyping machines that can crank out a plastic model overnight. If one of those stainless steel blades is off by the radius of human hair 40 micrometres the result is a bad shave. If the tip of the blade, with its coatings of ultra-hard carbon and Teflon-like material, is out by a tenth of a nanometre, a billionth of a metre, same thing. "We're talking about hundreds of atoms here. You just won't find another mass-produced consumer product good that has to do that. So it's absolutely phenomenal the level of precision that guys demand."

Sheez, we are hard to please.

If you have been thinking about those two blades in 1971 and wondering how many blades will be enough, the answer seems to be about five plus one on the back.

Powell says the number of blades is "pretty well optimised", and "a good shave is about skin management" more than an increasing number of blades.

Powell says his customers still see value for money in the latest razors (as do thieves razor blades are the items most often stolen from supermarkets). "We would never put out anything that is not something that he wants and that delivers on what he wants.

"There is never a gimmick we only put in to these razors what physically deliver for customers. I am sure there are price points at which the benefit that you're giving does not equal the price point. What we call the consumer value equation.

"But quite frankly, we are mostly definitely not there."