Yes, New Materials

by Mike O’Brien

“The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun.” —Ecclesiastes 1:9

“Bullshit.” —Mike O’Brien 04-04-2022

It is a strange enough thing to collect knives. It is a step stranger still to collect sharpening stones; a further abstraction from reality, an auxiliary activity supporting a hobby which is itself a pantomime of preparedness and practicality. No matter. Once one is lodged firmly enough down a rabbit hole, the only options available are to hope for rescue, or to keep crawling deeper. I have clearly chosen the latter.

The two collection are, in principle, complimentary. Or they would be, if my knife collection served any use that would engender a need for resharpening. As it is, they remain pristinely polished and razor sharp, to no wordly end. The fact that their polished edges are also sharp is almost incidental; the added challenge of making them both polished and sharp is an undertaking of curiosity, contemplative time-wasting, and vain self-overcoming. Still, it’s cheaper than collecting cars, with far less surface area over which to preen.

Of course, function is a factor in this appreciation. The marvel of an alloy hard enough to cut glass is that it can cut glass, in addition to the marvel of our ability to produce such an alloy. Diamonds can cut glass, but you can’t make a reasonably priced pocket knife out of diamonds (actually… well, it’s complicated). But an alloy that can cut glass, while being transformable into a shape of our choosing, and while also being re-sharpenable after God-know-what manner of use managed to dull it, is something more special still. It is an example of human ingenuity’s power to manipulate natural substances to suit whatever specialized application we may devise. It is awe-inspiring, both in the sense of wonderment and dread.

The pas-de-deux of steel and sharpeners is a spectacle of such ingenuity pitted against itself. As steel companies offered blades made of harder-wearing materials, the sharpening media that sufficed to service simple steels for millennia became inadequate. New materials begat new materials, and when better sharpening tools became widely available, better steels became a feasible option for a wider market. And so on. The scale of improvement is striking: a simple carbon steel, virtually the only kind in use prior to the late 19th century, keeps its edge for about a tenth as long as the best cutting steels currently available. Compared to the best non-steel blades available, that ratio falls to about 1/20. Does anyone need such superlative qualities to open their packages or prepare their meals? No, of course not. But need is not the issue. It is a sublime pleasure to possess such things, knowing that they owe their existence to vast investments of knowledge and power unimaginable to our forebears.

The practical benefit of these wonderous materials is that they rarely need to be sharpened. But where is the fun in that? To feel fully invested with the powers of industrial civilization, one ought to be able to maintain these store-bought Excaliburs by oneself. And thus we feel the seductive draw of the fancy sharpener: to wield an implement of such rarefied qualities that no common matter can resist it, and to wield another implement of such rarefied qualities that it can shape the former. The immovable object in one hand, and the irresistible force in the other. It is emblematic of our membership in a tribe that can accomplish heroic things, like wearing a NASA hat or a Ferrari jersey. We may never fly a spaceship or pilot an F1 car, but by gum we’re in the club.

Prior to the scientific maturation of materials engineering, improvements in steel and in sharpening were largely provided by serendipitous gifts of nature (had She known where all this was heading, she might have kept her secrets). Ore happened to be purer in one place than another, helpful traces of rare metals happened to infiltrate a particular seam, minerals happened to find each other in just the right stratum of rock, under just the right amount of pressure and heat. Such treasures were recognized and prized, and some still yield fruit to this day. The story of these materials is the story of Earth itself, both of the continuous processes of geology and of punctuating events, be they tectonic, igneous, or ecological.

My most recent acquisition, for instance, is a Belgian yellow coticule. So called because it is mined in the Belgian Ardennes, and it is yellow, and “cos” is Latin for whetstone. These stones have been used since Roman times, if not earlier (in fact, the areas where this stone abounded were seized and exploited by the Romans for their own sharpening needs). It is a favourite of razor honers because it is extremely fine, and because its coarseness can be increased by creating a slurry on its surface, allowing the same stone to both shape and finish an edge. I do have an antique straight razor in need of restoration, so I’d say this was a rational investment. I’d never shave with it, of course. It scares me. But it deserves to be restored to its former glory, even if it never cuts another whisker. How can an inanimate object deserve one fate over another? I don’t know. I’m just just intuiting the natural order of things.

The natural history of the stone is perhaps even more interesting than its cultural history. I say perhaps, because the most recent academic literature seems to be inconclusive about the material’s origins. Worse, it appears to dash my initial notions, which were that a volcanic eruption 480 million years ago spewed forth aerosolized, 10-micron-wide garnets (aluminium manganese silicate, or “spessartine” to its friends), which were covered over by sediment and fused into a solid layer over geological time. The volcanic part is apparently dubious, which saddens me because I like the “forged in the fires of Mount Doom” aspect of my rock’s story. It likely is more a case of slow chemical transformation and crystal precipitation, which is still pretty cool to a reader of Darwin (and therefor an indirect student of Lyell). However it came about, it consists of an unusually high concentration of 12-sided crystal balls hard enough to abrade vanadium and tungsten, nestled in a mica-quartz cake such that just the tops of these magical soccer balls are exposed. Being near-spherical in shape, they are tough relative to their surface hardness, and they abrade finely relative to their diameter, punching far above their weight, tribologically speaking.

To design such a material, and to design a method by which to produce it, would be a feat of cumulative technical genius. Its happenstance natural occurrence brings to mind debates in aesthetic philosophy, about the status of beautiful found objects like worn stones and driftwood. Does art just happen in the course of natural processes? Are the works of human artists complex instances of art “just happening” through our bodies? Like any debate about the rules for stipulating values, it is probably as irresolvable as it is engaging.

I have as yet avoided the rabbit holes associated with other regionally specific natural sharpeners, those principally being Arkansas stones and the various Japanese natural stones. The former are a flinty form of silica found in Arkansas, Oklahoma and Texas, used by native peoples of those regions (and, presumably, by the peoples with whom they traded) for making cutting tools. Now that steel does most of the cutting work, Arkansas stone has been relegated to maintaining the material that took its job. I’d be flinty too, if I suffered such an indignity. Japan has as many kinds of sharpening stones as they have kinds of knives, and they have too many kinds of knives (I say this as someone who delights in a endless variety of knives). The foreign over-admirers of Japanese culture have a tendency to assume that the painstaking traditional methods of that country are dictated by a sublime understanding of nature and craft. In fact, as in any other country, many of their traditions are historical accidents that work well enough to stick around. The fetishization of Japanese knives is a world unto itself, with “correct” methods not only for sharpening but also for polishing the non-cutting parts of a blade, and names for each kind of finish. As such, there are natural stones from this corner of that mountain, mined during such and such a period, which are prized not because the finish they leave is superior in any practical way, but because it is “correct”. That is no better or worse a reason than my own absurdities. I am just glad that this particular form of madness has no hold on me. The natural history of these stones is more biological than most, their abrasive particles being the shells of long-expired microscopic ocean animals, deposited in layers on the sea floor and swept ashore in geological displacements. And now, in their posterity, they sharpen the world’s finest seafood cutlery. The Japanese sure do take things littorally.

On the synthetic side of the sharpening aisle, materials have advanced to the point where diamonds are not clearly the supreme substance, nor are they a particularly expensive option. As a by-product of grinding large diamonds, very small diamonds (from 100 to 0.1 microns) are in fact quite plentiful and cheap, though none of them would stand out in a Tiffany’s display. Synthetic diamonds are also cheap and plentiful (don’t let the legacy diamond mafia tell you different). If diamond isn’t good enough for you, there’s cubic boron nitride (CBN), not quite as hard but a good bit tougher, and more expensive. (More expensive than diamonds, yet still quite reasonable, all things considered. That’s the conceptual space I inhabit, folks.)

The rub for abrasive applications is that, while diamonds and CBN and are very hard and stable, it is difficult to affix them to a host surface in a manner befitting their own strength. This usually means embedding them in a molten layer of nickel atop a steel plate, or in a resinous film. But the new kid on the sharpening block, the ne-plus-ultra of scraping small bits of expensive stuff with other small bits of expensive stuff, resembles the natural tricks exhibited in the coticule. The abrasives are mixed into a resin and cured, or, for even more money, they are mixed with ceramic filler which is then molten and vitrified, creating a diamond-impregnated glass that cuts the hardest carbides without noticeable wear. All of this is a curio and a luxury, unless you have voluntarily burdened yourself with the necessity of sharpening absurdly hard-wearing steel. Or, perhaps you sharpen other people’s absurdly hard-wearing steel for a living, although I have never heard of such a person who did not also own an unreasonable amount of knives and sharpeners for themselves. The professional is a post-hoc justification for the personal.

As you might imagine, I have considered getting some of these state-of-the-art trinkets for myself. As luck would have it, the cheap ones are Russian, and thus morally untenable in the present situation, while the expensive ones are sold out (and very expensive indeed), and thus unobtainable. Given the internal illogic that characterizes this hobby, such external impediments are the only real source of restraint, and I am thankful for them. Grant me continence, but not for too long. I am also in a stable equilibrium with my current collection, in that I can sharpen all the knives I have with all the sharpeners I have, and there are no new knives that I find irresistible at the moment. Well, not quite. As a materials nerd, two developments have piqued my interest, though neither compel me to be an early adopter just yet.

The first is high-impact ceramic, a special blend of zirconium oxide and yttrium oxide that has the hardness of tungsten carbide and the flexibility of steel, while also being completely stainless. In addition, it can be softened for ease of machining, then hardened for final use, just like steel. I witnessed glimpses of its development on Youtube, as one of my favourite steel experts (Roman at Kasé Knives Switzerland) was asked to consult on how to process it into blades. It’s a strange kind of pride to be one of a few hundred people in the world (going by Youtube views) to witness a new substance being born, first hearing explanations of the how and why of its composition, and then seeing it manifested in an object and tested to reveal its actual properties. As of yet I’ve only seen it used by a single Swiss company, and Swiss shipping rates are eye-watering. Between my cheapness and the possible-but-punishing sharpening characteristics of this new material, I will stay firmly planted on the fence for now. I am curious to see what kind of industrial applications this materials finds its way into; its development seems far too laborious for a mere culinary niche.

The second wonder material is another substance whose birthing I witnessed, not long after the first. As long as there has been stainless steel, there has been a problem with stainless steel. That problem is chromium carbide. Chromium makes steel stainless, while carbon makes steel, well, steel. Add about 0.3%-1.0% carbon to iron and heat it to around 800°C, and it transitions to a phase called austenite. Quench that austenite rapidly in water or oil, and it turns into martensite, which is the hard phase used for blades, springs, files, and other demanding applications. In a stainless steel (13% or more chromium, generally), any carbon added over the iron matrix’s saturation point (about 0.7%) will form chromium carbides, pulling chromium out of solution and reducing stainlessness. One solution is to keep the carbon and chromium at just under the threshold for creating carbides. This limitation of this approach is that you often want carbides, because they make the steel harder and more wear-resistant, like aggregates in concrete. You don’t necessarily want chromium carbides, though, because they are softer than more desirable forms like vanadium carbide, and because the individual carbide chunks can grow to the point that they weaken the steel, like oversized chocolate chips in a cookie.

For over a century, different balancing acts have been attempted, adding more chromium and more carbon along with various other elements to avoid the worst consequences of exceeding the carbon saturation (or “eutectoid”) threshold. Some very good steels have resulted, but none of them matched the toughness of stainless steels below that threshold, or non-stainless steels of both low and high alloy contents. Until last year, that is, when a metallurgist named Dr Larrin Thomas, whose blog I have been following religiously (aptly named “Knife Steel Nerds”) announced that he had designed a steel of his own, called “Magnacut”, which solved the chromium carbide problem. As with the high-impact ceramic, first came the explanations of how and why this solution would work, which seemed quite credible to my own lay self but could have been an extremely elaborate prank. The short version is that, by carefully balancing elements using computerized thermodynamic modelling, he was able to add just enough chromium to inhibit corrosion, while using other more powerful carbide-forming elements like niobium and vanadium to bind up all the excess carbon. The result, in theory, is a properly stainless steel than is as tough as non-stainless steels with comparable levels of alloy. The result in practice is the second-most stainless steel on the market, with toughness and hardness exceeding predictions to boot. (It is fairly easy to sharpen, too, so if I were to get some, I wouldn’t need more sharpening equipment. Just saying…).

This may not excite those of you with well-ordered habits of conspicuous consumption. To me, it is cause for wonderment, that a single person could solve an engineering riddle that has stumped the steel industry for over a century. (It should be noted that developing cutlery steel is not Dr Thomas’ job. He revolutionized stainless steel in his spare time). Granted, he stood on the shoulders of giants, and computers did a lot of heavy lifting. But his solution is such a lateral step from the incremental shufflings of previous approaches, it serves as a reminder than some problems, however seemingly intractable, can be solved. Cases such as Dr Thomas’ wonder-steel, or the flexing fantastic ceramic, remind me that some new solutions are still discoverable, and that some zero-sum games are escapable.

I am only talking about engineering problems, mind you. We’re still a dead-end species. But we can still pull off a few more tricks before the show is over.