I have posted initial results of experiments testing my new powder metallurgy knife steel. So come join Patreon if you want to see how the steel is doing before everyone else. Professor John Verhoeven contacted me recently about a small study he did about how razor blades dull. Verhoeven is well known in the knife community for writing Steel Metallurgy for the Non-Metallurgist , a now classic text introducing metallurgy to knifemakers and bladesmiths. This recent study on razor blades was to look at the contribution of micro-chipping on the dulling of razor blades, as a popular journal article recently came out on this mechanism, published in Science.
So enough of my commentary, on to his article. Razor blades can dull by 4 mechanisms, corrosion of the steel, wear from contact with whiskers, formation of evaporites due to inadequate drying and the microchipping formation produced by contacts with whiskers. The last mechanism was only recently discovered [2] and the purpose of this study was to determine if microchip formation plays a significant role in dulling razor blades during shaving.
Experiments have been carried out with properly cleaned blades showing that after as many as shaves the fraction of the blade length occupied by microchips was still not sufficient to give rise to a significant reduction in shaving smoothness.
The double edge razor was invented by Gillette in and was the most popular blade into the early s. The blades were made of carbon steel and coated with an oily substance to avoid corrosion.
In the early s the British firm, Wilkinson Sword, began using stainless steel blades and the large American companies quickly followed suit. In Gillette introduced the cartridge razor which contained 2 very narrow blades packaged in a cartridge that could be easily removed from a handle.
They are now produced by several different companies and have evolved into cartridges with 3 to 5 blades. The blades are made of a martensitic stainless steel and the sharpened edges are coated with a polyfloride to reduce friction and the cartridges contain one or more lubricating strips that purportedly make for a smoother shave. The Gillette Mach 3, which the author uses, has a moisturizing strip above the 3 blades which releases a blue substance to reduce friction but becomes significantly depleted after around a dozen shaves.
The cartridge razor blades are now the most popular type of razor. The steel contains very small spherically shaped Cr carbides distributed throughout the interior. Two Swedish steel companies supply much of the steel, Uddeholm and Sandvik.
See ref. The steel is supplied from the mill as thin strips. The hardness of whisker hair is much less than that of the steel and one would expect wear of the steel would be very small. Reference [2] presents hardness data of whiskers showing them to be softer than the blades by a factor of The edge of a razor blade is sharpened to a very small radius, on the order of 0. Wear would be expected to round the sharp edge and dull the blade. But because the blades are 50 times harder than the hair follicles, one would not expect much wear during shaving.
There are two obvious ways that these steel razor blade would dull, wear on repeated contact with whiskers and corrosion of the steel at the sharpened edge. However, there is an additional mechanism causing blades to dull that is not well recognized. Most water supplies have some level of mineral impurities in them, notably carbonates. If this water is left on the edge of a blade after shaving, in addition to promoting corrosion, it will evaporate and leave a thin layer of an evaporite, such as calcium carbonate on the cutting edge which will dull the blade.
The cartridge razors with 3 to 5 blades are difficult to dry properly due to the small distance between blades and are subject to dulling if the water is not removed from the blades prior to evaporation. There is a wide perception on the internet that the cartridges need to be replaced after only a week or two, following is a quote from the web:.
On average, a man shaving daily should expect his razor blade to last around a week. An analysis of the magnified blades showed that they did not chip when they cut the hair perpendicularly but did so more often when the blade met the hairs at an angle. Computer simulations derived from the collected data showed that it wasn't just the angle was important, but also the consistency of the steel in the blade.
If metal varied along the edge, this produced weak spots where chips could occur. In hopes of improving blade quality, the team has filed for a provisional patent for a process to make razor steel more homogeneous. The research was published in Science.
Source: MIT. LOG IN. Menu HOME. Search Query Submit Search. By David Szondy. Facebook Twitter Flipboard LinkedIn. Science has discovered why razor blades go dull even though the hairs they cut are much softer than steel. View 1 Image. David Szondy. David Szondy is a freelance journalist, playwright, and general scribbler based in Seattle, Washington.
A retired field archaeologist and university lecturer, he has a background in the history of science, technology, and medicine with a particular emphasis on aerospace, military, and cybernetic subjects. In addition, he is the author of a number of websites, four award-winning plays, a novel that has thankfully vanished from history, reviews, scholarly works ranging from industrial archaeology to law, and has worked as a feature writer for several international magazines.
He has been a New Atlas contributor since Popular Stories. Load More. Tasan says commercial disposable razors—those marketed to both men and women—typically use the same type of steel but have different coatings and numbers of blades in the cartridge.
Razors marketed to men and women are similar except for handle design and the number of blades. He says three factors affect how fast razor blades get dull: the angle that the blade cuts against the hair, the microstructural uniformity of the steel-carbide alloy, and the presence of microcracks in the steel surface that occur in manufacturing during the honing process, in which the blade is sharpened by rubbing it against a coarse surface.
One shaving industry professional says that consumers are not worried as much about how long the metal blade lasts, but rather about its performance during each shave. The trick in designing a cartridge is finding that balance. Bryan Webler, an associate professor of materials science at Carnegie Mellon University, says the MIT study is a good example of identifying why a material performs the way it does. Mike Wehner has reported on technology and video games for the past decade, covering breaking news and trends in VR, wearables, smartphones, and future tech.
His love of reporting is second only to his gaming addiction. By Mike Wehner. A new study took a microscopic look at razors to determine why they go dull when cutting soft material such as hair. The team found that the angle of the hair can have a big impact on how dull the blade gets after cutting through it.
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