Knife Edges Under Magnification

Fallkniven White Whale

 - This specimen comes straight from my kitchen, nothing folding or tactical here :) However, this guy sees more use then few of the knives above combined. Well, what can you do, kitchen... We all have to eat. So, now you know this knife is a user.
Another important piece of info, this is VG-10 stainless steel. Rockwell hardness around 59HRC. Which is pretty high for a kitchen knife. However, I have no complaints, works like a charm. What's special about this blade is the fact that it has mirror polish. In general I don't use mirror polished edges in the kitchen. Since mainly I do slicing in there, and not chopping or push cutting. However, this santoku gets used mostly for vegetable cutting or chopping, and whenever it's cutting, the motion is still push cutting, not slicing, thus the mirror polished edge. Here it is in it's original state. The edge itself had nice satin finish originally and was rather convex. After I've sharpened it several time using the same mousepad/sandpaper method (to be precise mousepad and abrasive films for last year) it acquired mirror polished convex edge. As for its sharpness, well it's a match for the looks. You wouldn't say that looking at those pictures anyway. It's hard to tell from the pictures, but the yellowish part of the edge is the satin finish, and the lighter part, which looks more scratched is the mirror polished convex section. Coloring is different because the difference in light reflecting properties of two different sections of the steel. For this picture I was using natural light. Magnification for both of them is ~32x. In other words those are 1024x768 crops from the original image of 3072x2048 size.

SRKW Bog Dog

 - Yet another field knife that ended up in my kitchen because it was performing well in there, and of course because I had to use it more often. Anyway, Bog Dog is one more D2 blade I have in edge macro study. As a kitchen knife that little knife sees a lot of use, and because it's the kitchen it is a lot of abuse as well. D2 being semi stainless means it needs more care then stainless steels. As a reminder stainless steel doesn't mean it won't rust if you don't take care of it. Anyway, D2 steel blade, sharpened first with edge pro to 15 degree edge per side, making 30° included. Later the usual maintenance with abrasive films, 5µm SiC and then 0.3µm Al₂O₃. To see how this blade looks in real life check out this picture. As you can see it is mirror polished, gleaming sharp and all that. Now let's take a closer look.
As you have already expected the close up 32x doesn't look as pretty. Multiple scratches, swirls and all the mess is there. Still, compared to some other edges that look same polished visually this one looks smoother under strong magnification. Once again, grain size didn't play any significant role in polishing and smoothness, at least up to 32x factor. Details are good enough to clearly see convex edge tip which is a result of using mousepad/abrasive film combo on this knife for continued time. Original edge was standard V shape thanks to Edge-Pro, but later abrasives on soft base produced nice convex edge. In general I wouldn't use mirror polished edge on the knife intended for the kitchen, but this one, i.e. Bog Dog didn't start its life as a kitchen knife and then I was experimenting with various edge types and polish levels in the kitchen as well, so for the time being I just keep it like that, to do comparative cutting tests. In the end, even though it looks pretty toothy at 32x magnification the edge behaves as it looks to unarmed eye, that is mirror polished one. Very good push cutter, but has sliding problems on certain cutting mediums, such as tomato skin...

Rinaldi TTKK

 - That was the only custom piece in my collection that was made specifically for the kitchen use for a long time. Today I have 40+ kitchen knives, most of them custom and semi-custom (see kitchen knife reviews). And that is where it lived all the time, ok minus shipping :) As you can guess the blade has seen a lot of use, rather abusive use. Even though, I do take very good care of my knives, there's nothing one can do in the kitchen, blades get in not very friendly environment, and have to work there. Although that one(TTKK) has no problems. I asked the maker to use S30V steel, which back then was the newest and hottest super steel that one could supposedly get and dream of :) Well, it's still hot today, but less hyped. It's a good steel overall. As usual, let's see what was the edge look like in the beginning - this is the photo depicting TTKK in its original working condition.
As I've mentioned few times, in that period(2004-2008) I don't have mirror polished edges on kitchen knives, so TTKK had the edge finished at 600 grit sandpaper all the time. Unfortunately I don't have magnified picture of that. Later, once I started experimenting with macros I decided to study edge degradation in the kitchen and TTKK was the subject. Results of that study are yet to be published here, but for starters I resharpened TTKK to 15° angle edge (per side) and mirror polished it using Edge-Pro Apex sharpening system, then I've used 0.3µm Al₂O₃ to finish it, and convex the edge as well. The result is top picture in the stack on the left. I'd say pretty clearly mirror polished, relatively thin edge.
And the next two pictures show the close up with 32x magnification. By know, you already know it's gonna look scary :) But not too scary for some reason. Second picture, or in other words first macro view shows mid section of the TTKK. As you can see mostly it's pretty smooth, I mean the edge. However satin finish on the blade does look rough, especially compared to Lochsa blade, which is also satin, but the difference is visible with naked eye as well. As for the TTKK edge you can clearly see scratches from Edge Pro rough stone at the edge base, which demonstrates why you should cover the blade with painters tape prior to using edge pro :) That is in case if you mind those scratches. The edge itself does have lots of scratches as well. Those are not easily visible with naked eye though. Still, closer to the right, you can see where I applied excessive pressure on edge pro 120 grit stone the scratches formed too deep and later higher grits were unable to polish them out. Another point, don't use too much pressure when sharpening, especially with rough stones. And finally we see the convex formed by 0.3µm Al₂O₃ abrasive, that's the darker line marked with two red arrows.
And the last picture, the third one in the stack, shows the TTKK blade tip. This looks rougher than the mid section. Again, that's because of high pressure when using edge pro, low grit stone. All in all, this is a good illustration of what excessive pressure can do to the edge, even if you don't see it with naked eye. Because those rough spots do matter when cutting and especially chopping. Less likely I'll have to chop with TTKK anything significant (if anything at all) having over a dozen Kukris and dozens of large field knives, but still, if you want fine, nicely polished edge, light pressure at all grits is the key.

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