What makes something "sharper?"

What makes something "sharper?"

When I started Vivront I wondered out loud to a friend if I could build it and never sharpen a knife. The idea there was to focus on one thing - selling. However, with true curiosity and a desire to stand independently with expertise in the space, I decided to not only learn to sharpen but also to acquire a commercial machine capable of sharpening, and sharpening well, at scale and with speed.

So, what the hell does it mean for something to be sharp much less “sharper” than before or something else?

Bit #1 • Wood is sharper than metal?

Eight days ago the nytimes.com scored an enormous win for the PR team of some “scientists.” The article was titled “A Wooden Knife Sharper Than Steel? Scientists Say So.” Yet, the URL includes “hardened-wood-knife-history” in it. I suspect that an editor somewhere decided to capitalize on all of us readers and our collective lack of knowledge on sharpness and modified the title to something more “clickable.”

In following knife stuff, I’ve subscribed to the Knife Steel Nerds blog. My goal is to slowly understand metallurgy in more depth. Larrin, who writes the blog, had the nytimes article sent to him by numerous persons, as did I. Yet, with his ninja skills and metal mind, Larrin dug in and wrote about it in this post “Wood Knife that is 3x Sharper than Steel? Spoiler: No.”

It turns out the wood knife in question was being compared to “commercial table knives,” something left out of the nytimes article. That’s an overly technical description that conveniently conceals that the metal “knife” in question is a butter knife.

As Larrin points out, and you know from experience, butter knives are by design not intended to be sharp. Their very construction commonly has a 90 degree blunt portion of the “cutting” edge with some micro serrations. You know, for butter. No wonder the pointed, er sharpened and hardened, wood knife was made to be sharper than “steel” when compared with a notably dull steel knife in their “study.” Sneaky.

Bit #2 • So, how does one measure “sharpness?

On one hand, you can pick up a knife, use it and then compare it to another knife on a similar cut. Likely, since we don’t commonly service our knives, both are “dull” subjectively and experientially. On the other hand, it’d be wonderful to have an external measure of sharpness, one with more objective characteristics.

One of the more objective ways to measure sharpness is a pressure sensor and a uniform piece of media that is cut in a test. In doing so one could measure the grams of force required to cut the same media from knife to knife or sharpening to sharpening.

The frequently used tool for such a measurement is an Edge on Up tester with BESS media. Here’s a screenshot of a testing and a link.

The "Brubacher Edge Sharpness Scale" or BESS, available below, is relatively young. Mike Brubacher, conceived of it in 2012 in his efforts to build an objective measure of sharpness. Check out the common measure of a butter knife at 2000 grams of force to cut the media.

I’ve been testing knives coming into the shop before and after sharpening. I’ve also been testing knives over time and use with the BESS system.

The dullest knives sent for sharpening have measured 1500+. Per the BESS scale, edges above 400 are in need of service. We’re sharpening and returning knives that measure under 300 on a regular basis. No wonder why people experience their knives as “sharp” when they get them back and start using them. They are often 4 times as sharp as when shipped to us. And now we know quantitatively what we knew qualitatively.

Bit #3 • Practicing sharp

A recent customer’s knife sharpness measurement before service.
One of the things I’ve been practicing on the machine is how to make a knife sharp in a predictable and repeatable fashion. I’ve been measuring the same knife in the same session as well as as they dull over time.

In the process of sharpening the same knife over and over I’ve been able to produce an edge that measures ~300, predictably. I’m also learning how to purposely produce an edge at 400, or 500 (BTW, this is not possible with the vast majority of DIY sharpeners from the Amazon or else). Edges under 200, or razor blade sharp, are achievable but not as predictably as I’d like. We’ll work on it. I do know that it’s easier to produce edges under 300 on higher quality knives with higher quality steel right now (reason some knives are more expensive than others). It’ll come. I’ll stay focused.

In the process of using knives and measuring their sharpness over time I’m finding our kitchen knives to lose roughly 50% of their sharpness, as measured on the BESS scale, every 2-3 months when they are also NOT honed. I’m purposely not honing right now because most of us don’t and I want to know how long edges “last” when not honed. Our knives regularly measure in the 500s after 2-3 months when they started in the 200’s.

Ok. So there it is. Three bits for a Tuesday. A PR team dunked on the nytimes last week. A knife’s sharpness can be objectively measured in grams of force to cut a standard piece of test media. The sharpness of a knife can be purposely applied as more or less sharp by a skilled sharpener with custom tools.

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