People who sharpen blades with any regularity eventually learn to discern the quality of their edges. We each have the methods that work for us. For some ceremoniously and effortlessly, slicing thin magazines or the nearly extinct telephone book pages are popular ways of assessing an edge. Using super thin paper offers an auditory means for detecting even the most minor chips. Having the blade bite while sliding it on a thumb or fingernail is another quick, simple test. Then there’s the ever-popular – with some males anyway – arm-hair shaving. If you’re showing off, you’ll demonstrate how you can whittle a single strand of hair! So, with all that said, how sharp is your knife, exactly? Great question!
“Adjectively Sharp” or Good Enough
Early on, the problem for me as a self-taught knife sharpening specialist was that I had no relative frame of reference for determining sharpness compared to other blades. I didn’t know what I didn’t know about how sharp an edge could get and how to measure it. Terms like wicked sharp, scary sharp, etc., mean nothing without some frame of reference. I call these terms “adjectively sharp” All I knew was that once I could shave arm hair cleanly, my edge was decent. And good enough.
Objective Standard Frame of Reference
The job was complete once I could shave arm hair after using run-of-the-mill Arkansas stones and oil. For most of us, we sharpen until it’s good enough to perform the intended task, whether that’s filleting a fish or cutting rope. Testing an edge by slicing paper is quick and easy, but the problem is which paper? How thick is the sheet? Is the paper coated? With the grain or against it? Push cutting a blade through thin phone book paper is different than, say, push-cutting 100 lbs printer paper, but what does that mean? Which is sharper? Is shaving my fine arm hair the same as shaving thick bush-like arm hair?
YouTube, Internet Forums, Created Defacto Standard Sharpness Tests
With the emergence of the Internet, online forums, and YouTube channels, knife sharpening enthusiasts began to sort out simple, cost-effective ways to communicate the sharpness of their edges. To assess my edge vs. yours, virtually, clever reference standards have emerged based on specific products like a particular cigarette rolling paper. As it happens, successfully push-cutting a knife blade into a specific brand of cigarette paper means you have a very sharp edge. Anything less is immediately apparent. Of course, this specific test can be fooled with a useless superfine foil edge too, which means it’s sharp, but folds like a lawn chair and dulls if you cut into anything solid. The cigarette paper test offers a standard reference upon which we can evaluate our edges on some level, but this still falls short of helping us to understand what it means.
But, How Sharp Is The Blade?
For me, the problem is both determining relative sharpness against some consistent, repeatable standard. So, while I know my polished 6000 grit chef knife-edge glides effortlessly through a light catalog sheet of paper, what do I know? Well, I know it’s certainly a useable edge in the kitchen. And, I also know that there are no chips I’dI’d hear them slightly interrupting the slicing. I could achieve this test with an improperly de-burred edge too, which means it would dull during first use on a cutting board, assuming that the knife is sharpened adequately for durability too (i.e., de-burred).
Needed: A Standard Scale and Measurement Method for determining Sharpness.
What’s missing is a way to know, beyond doubt, that a particular effort or sound or feel of the paper test is akin to some objective and quantifiable standard. Moreover, it would be nice to send our sharpened knife to another person knowing they will get the same result when they test the edge using the same method & scale. So we need a replicable process with as few variables as possible, and we also need a means for quantifying the results. We need a method, and we need a standard measuring scale. If I measure and conclude a sharpness of 10 using method ABC, you should also get the same result using method ABC. Make sense? Once you know that a particular sharpness method equates to a well-known and repeatable standard, you know the relative sharpness of your edge. So, what standard should we use? Another good question. That’s where BESS comes in. Let’s meet BESS.
The BESS Sharpness Test System
The BESS system is relatively easy to understand. You have a specially modified scale that measures grams that records the downward force required to sever a certified test media (resembles a piece of fishing line). After recording the amount of force in grams, the result compares with a published scale equating to common commercial edges indicating relative sharpness. For example, I believe most people would agree that a double-edge razor blade, out of the package, is very sharp. It is very sharp and requires very little force in grams to sever the media, which results in a low BESS number. Conversely, a regular butter knife is quite dull and requires a significant effort to sever the test media resulting in a high BESS number. As you might imagine, there are many levels of sharpness between a dull butter knife and a fresh double-edge razor blade. That is where the BESS C-Scale comes into play. The BESS C Scale is our standard of reference. Once you’ve sharpened and tested enough knives using a BESS tester, you quickly learn how to gauge sharpness using more straightforward quick methods. In other words, experience tells you that a 200 BESS edge equates to a particular sound as it slices through your favorite catalog paper. A 200 BESS edge is dang sharp. Really sharp. I would venture a guess that most people think that they’re getting a sharper edge than reality. I know this was true for me.
My Case for the BESS Sharpness Tester
I bought into the BESS system not because of the mechanism but because of the standardized test media. We MUST have widely available and highly consistent standard test media for this system to work. In this case, it resembles a kind of suture material or monofilament fishing line. Several folks have approximated various off-the-shelf fishing lines as low-cost bulk test media alternatives, but the inconsistencies of nylon monofilament are well known and documented. The BESS test media does more than test for relative sharpness vs. a quasi-standard BESS C scale. The test also exposes an improperly de-burred foil edge instantly too. Still, there are flaws with the BESS system. For example, knowing, for sure, that you have identical test media tension for successive tests takes some special effort. The community overcomes the variable tension concern by using a standard laboratory weight to tighten the line between each new test consistently. As for me, I use a 100-gram certified calibration weight to tension line when improved consistency is needed. The challenge has been establishing a reasonable repeatable standard to communicate relative sharpness in a quantifiable manner. Right now, other than cigarette paper push cuts, the BESS standard, method, and test media seem to be the standard to beat.
BESS System Cost
The equipment and test mechanism costs aren’t what I consider ridiculously expensive. However, depending on the options and test frequency, the BESS system is certainly not what I would call cheap either. Then again, if you are into excellent knives and hand sharpening, I’ll wager you spent a fair amount of money on that stuff. The entry-level PT-50c will set you back around USD 150.00 as of Jan 2022. The Pro is around $180.00, and Industrial PT50A goes for about $269.00 and offers 1g measurement increments if you want more detail. The cost of a decent or real-decent new knife. You get a fair amount of test media and all the stuff required in the kits above. Additional spools of test media are relatively low cost, and all the above is available directly from Edge-On-Up online, which is how I bought mine. It’s worth noting that this is NOT an advertisement for the product, and I do not profit if you elect to buy a BESS PT50 tester. But, I do believe in what the product does and offers me.
Note: Whether you agree with the usefulness of the BESS system or not, there is no denying that most understand it. Any seasoned sharpener quickly assesses and knows the degree of sharpness and quality of a polished or toothy apex without the BESS scale. Still, having access to the BESS system, or some kind of easily replicable standard, only serves to keep you on top of your game and communicate the quality of your work a little more meaningfully than random paper or arm hair shaving demonstrations. By nature, many people do not like to be measured. Ignorance is bliss for some folks, I suppose. That’s ok, as far as I’m concerned. But it does get me riled up when detractors say the test is useless or meaningless. Not only are they wrong, but I can almost guarantee that their edges are not as good as they think they are, yet they’ll never know. These are the same people who believe all kinds of myths and misinformation about abrasives and steel. Ok, enough of the soapbox, where was I?
BESS Limitations For Knife Edge Testing
The BESS system measures the sharpness of an excellent durable edge using a push cut. Each measurement is one tiny spot along the edge on the apex of the blade edge. It does not test slicing; at least the BESS PT50 systems don’t. However, Edge-On-Up has introduced some testers that do test slicing and push cutting sharpness in one system. For that system, you’ll now be forking over some pretty serious cash ($500+), that’s well outside my semi-professional sharpening needs.
Further, the PT50 system does not evaluate the durability of a given blade either. Even though the BESS PT-50 exposes an improperly de-burred or foil edge easily with a terrible BESS number. Also, you can easily see the divot where the test media digs into the foil edge (improperly de-burred edge). Other than exposing foil edges, there is no way to know durability other than to retest manually after iterations of controlled test cuts on something like rope or cardboard and to compare the degradation results over time with other blades sharpened at the same bevel angles. In other words, you can evaluate blade durability by measuring the knife and then test cutting a control material a controlled number of times, using a controlled level of pressure, and then retesting to assess impact. There are folks out there that do this sort of thing and report their findings on the Internet. Knife designers, for example, might like to evaluate various steel options for a new knife, and durability testing would help them choose.
So, I ask you: how sharp is your knife, exactly? I hope this has been useful to you in your knife sharpening odyssey. I believe BESS is good for some of us obsessive edge types, but it’s certainly not for everybody. Either way, let me know your thoughts on the topic, especially if I got any of this wrong. Just be civil about it 😉