Grit and Microscopic Scratch Depth

In this experiment, I honed a razor as best I could with a hone that I will identify later (hone A). Then the razor was given 30 x strokes on a "finisher" that I will call "hone B"

The images are from the same location on the blade. I would like to know what "grit" would you assign to each hone, based on these images. The absolute value is obviously arbitrary, but at least give an indication of which is higher and by how much.

Scratches after the initial honing on "hone A"


After 30 x strokes on the "hone B"

It's very strange because the majority of the bevel done on hone 'b' looks smoother until you get very close to the edge where it actually looks rougher than hone 'a'.

My bet is that hone 'b' made the deeper scratches from hone 'a' more apparent.

I'll take a guess and say hone 'b' is a higher grit by about 3-4k. I'd place a in at around 8-10k and b around 12-15k.

Second part to my thinking is that while there may be more scratches from hone 'b', they look more plentiful yet finer.

For the sake of stimulating this discussion, I'll say hone A is 4000 grit higher than hone B.

These posts and photos are fantastic, thanks for bringing them to us.

Oh, another thrilling episode of 'Name that hone....' I think I can name that hone is 20 strokes Mike....

No guess as to the grit or micron rating but the difference between the individual abrasive grains as well as what can be seen of the edge is interesting. The first hone looks like it has rounder, less aggressive abrasive and judging by what looks like a slight raduis at the edge, was used with a slurry.

The second hone appears to have sharper, more aggressive cutting action. The invididual grain cuts are more pronounced. The second hone appears to have removed very little material but did make the edge much less radiused. So I would guess some type of more aggressive, sharper material such as diamond perhaps.

I would guess the first edge would also be less aggressive to shave with and perhaps feel what some describe as smoother. The second looks considerably sharper but less forgiving and perhaps more sensitive to the angle of the blade to the skid when shaving with it.

As always fascinating images.

Fuzzy Chops said:

In this experiment, I honed a razor as best I could with a hone that I will identify later (hone A). Then the razor was given 30 x strokes on a "finisher" that I will call "hone B"

The images are from the same location on the blade. I would like to know what "grit" would you assign to each hone, based on these images. The absolute value is obviously arbitrary, but at least give an indication of which is higher and by how much.

Scratches after the initial honing on "hone A"


After 30 x strokes on the "hone B"

Click to expand...

OOOOOO, fun.

Ignoring the big gaps in the edge (deep scratch that didn't get removed, pitting, crap on the hone, any idea (looks like a spot of pitting to me)?) and just going by scratch pattern (basing this on what I see with a crappier scope at ~1/10th the mag), I would have to guess that A is the finer hone, and is less than half the particle size. That said, it actually looks closer to a novaculite finish than a synth, with that odd buffed/polished down---rather than abraded look... but perhaps other finishes look like that using a SEM.

The bottom (B) vaguely reminds me of the results on a pasted strop, though that is probably just because I'm not used to seeing perpendicular to edge finishing scratches except from pastes. Whatever the case, the scratches look to my eyes to be much deeper at 5k than finish A's did. And I'd say even saying the particles are twice the size may be understating it. Just based on the 5k pics I wanna say the two finishes aren't even close. To my eyes there is almost no visible scratch pattern on A, and a rather deep one on B.

When will you tell us what these finishes really are?


Super secret bonus guess. Same finish, the background creates an optical illusion that one is different.

No idea really complete guesses

To me the frist one looks more natural, coticule just to throw one out

The second lloks synthetic, more aggressive, going to say Shapton Glass16K

Complete guesses

Awesome pics, I have said this before but I NEED a SEM

I'm very impressed with the replies so far. Let me add this image, showing the scratch pattern from a Shapton 8k GS. Not the same area as the above images but it gives a reference point for grit vs scratch depth.

What device is taking these pictures?

Scanning electron microscope, that's the "SEM" in the image text. An ion beam is used to section I believe, when the image shows a sectioned edge. That's a FIB, or focused ion beam.

I'm guessing the finer edge is around 20k-30k (remember the Gokumyo 20k and Shapton 30k are essentially the same grit), maybe as low as 15k. The coarser one maybe 8-10k.

Cheers, Steve

I am guessing Stone A is a very hard natural stone that is polished to a high shine, maybe just by using a slurry stone on it. Something in the Coti range.
Stone B looks synthetic, probably not polished to a high shine, just lapped with a DMT 325 or similar, that would account for the tight scratch pattern and the disproportionately rough edge. Although this appears to be a finer stone due to the tighter scratch pattern, I am guessing it is in the 8-10K range (American Standard, 5-6K JIS).

I would enjoy seeing a bunch of different stones and their corresponding edges under SEM. Maybe someday Fuzzy will have enough pictures to make a SEM thread.

With the slight convex shape of the fist shot, I would guess a slurry was was used but not seeing any normal coticule waste products, I don't think it was Belgian. Knowing you and your 20, Chops, I am pretty sure the finer grit is way up there and was used in conjunction with a lather made of maple syrup and polar bear urine. That dingleberry in the "nick" is the dead giveaway for PBU. Later, hoser. Denny

You guys are pretty sharp. har har.

Let me add the higher magnification images
After honing on stone A:



After 30 x-strokes on "hone B"

As you may have noticed, "hone B" imparts very fine scratches near the edge. In the optical microscope the bevel is reflective after "hone A" but "hone B" significantly improves the reflectivity and the bevel generally looks more polished. In the SEM, you can see that the increase in reflectivity does not correlate to a better polish at sub-micron scale.
Unfortunately, the region I chose to image suffered a small chip - this not typical of the edge elsewhere. If you look closely in the "hone A" images there is a hint that the area that chipped isn't completely solid.






Hone A is a Coticule and the edge was finished with clean water. I will say that this is very unusual Coticule, very hard, smooth as glass and very fast on water.
Hone B is 1 micron aluminum oxide lapping film from Thorlabs.

Now what grit ratings would you assign to these two 'hones?'

Very cool!
Please do one with plain 1um film, and one with 1um film + paper underneath! I am dying to see what the paper actually does in reality!

Wouldn't have thought that the coticule would leave such a smooth edge in comparison to the film! How's your HHT on them edges? Maybe we can clear that debate too! hahaha

Wow, I completely nailed that coti! I would say that was half skill, and half dumb luck .

I was way off on the second "stone", shame on me!

Cotis are commonly thought of as 10K stones. I had a very nice coti edge put on a razor once, sharp and very very smooth. It was not as sharp as the Chinese Natural I had, but SO much smoother.
1 micron is commonly thought to be 12K JIS.

Did you try shaving with both of these types of edges? Any preferences?

pmaster said:

Very cool!
Please do one with plain 1um film, and one with 1um film + paper underneath! I am dying to see what the paper actually does in reality!

Click to expand...

The high grit film produces slight micro-convexity and this may result in a foil edge in the same manner as stropping on sub-micron diamond. I explained this in another thread but the essence is that the flexibility of the edge leads to micro-concavity (and a foil edge) on the way to micro-convexity.

Here, honing on 0.3 micron lapping film (preceded by 3 micron and 1 micron). This razor has a geometrical bevel angle of 16.5 degrees. The measured angle shows a slight increase and a foil edge is evident.


The same film and razor, but with two sheets of wet paper beneath, shows a slightly increased angle as compared to film without paper and no evidence of a foil edge.

Thanks a lot for the explanations!

I'm still trying to wrap my head around things, but if i understand correctly, the paper underneath insures that there is no foil edge left when finishing the razor, at the same time resulting in bevel that is a bit more convex.

Thus I wonder if harsh-shaves (after 1um or other fine synthetics) is simply a result of these foil edges, which are still present and won't go away with simple stropping on leather. But then again there's the bevel angle that also comes into play, and the type of steel...

I never realized that there was some sort of flexibility at the edge, but I guess at this scale its logical.

Thanks again for clarifying a few things! I had been wondering about this for quite a while.

Fuzzy Chops said:

The high grit film produces slight micro-convexity and this may result in a foil edge in the same manner as stropping on sub-micron diamond. I explained this in another thread but the essence is that the flexibility of the edge leads to micro-concavity (and a foil edge) on the way to micro-convexity.

Here, honing on 0.3 micron lapping film (preceded by 3 micron and 1 micron). This razor has a geometrical bevel angle of 16.5 degrees. The measured angle shows a slight increase and a foil edge is evident.


The same film and razor, but with two sheets of wet paper beneath, shows a slightly increased angle as compared to film without paper and no evidence of a foil edge.

Click to expand...

How expensive are these microscopes??

More than most of our shaving dens combined . I think Fuzzy is using a university-purchased SEM (correct me if I am wrong).

Mmmm....Science.

Thanks for posting the pictures! Very interesting.

What is a foil edge and how do you spot it in that picture?