This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. Every review you see on this blog is bought with my own money. I have no affiliation to any manufacturer. The stones in this review were bartered for – a set of mine vs a set of these.

Review

Today’s sharpening stone is something very special. I’m frankly quite giddy as I am writing these lines – gentle readers, I am ecstatic to present you the review on the brandnew “Grain&Bond” – Sol Gel (SG) Sharpening stones – from Likhovtsov Abrasives Lab.

These sharpening stones were launched in the past 24 hours. They are the product of Alexander Likhovtsov, someone I consider a master in abrasives from Russia. The stones reviewed are two different grit sizes, F120 (120 µm) and F220 (63 µm).

Let’s dig into it:

The bright blue “F120” and “F220” SG stone. Do note: The stones being sold have a different laser engraving on the anodised aluminium blank.

The “SG” stands for sol-gel, the production process of the Al2O3 (Corund) abrasive these are based on. To expand, why this is exciting, you have to understand how aluminium oxide as an abrasive is made:

There are basically two methods in producing the popular abrasive. Large scale, one can melt Al2O3 into a large block, cool it down and then crush it into small pieces. These are then sorted by size, which makes for a very economic, hard powder. The individual grains themselves consist of only a few crystals, often micrometre sized.

The second industrial method is to mix precursors together, dry them until they form a gel, and then sinter the mixture before crushing and sorting for size. Here, each individual grain is polycrystalline, consisting out of a large number of often nanometre sized crystallites.

In their behaviour, they differ wildly. The molten Al2O3 dulls, and at some point fractures into large segments. The sol-gel Al2O3 meanwhile constantly exhibits micro fractures, that renew the cutting edge. This gives less of a glassy, dull feel during sharpening, but also a more homogeneous result. The downside to SG-Al2O3 is of course the cost – it costs multiple times more than regular melt-produced Al2O3.

You might ask: how does this translates to visible grain morphology? Don’t worry, I got you covered. Compare the SG grain with a similar sized molten Al2O3 grain, in the same binder:

Comparison in grain morphology between F220 sized grains – left/first picture is the SG-Al2O3, second/right picture is the molten AL2O3.

You can see that the SG-Al2O3 has a much smoother, flatter, and less ragged appearance. The molten Al2O3 initially shows a lot of ragged cutting edges from the crushing of the grain, but is also much more blocky – this is an increase in engagement volume, which makes cutting of hard steels more difficult, and typically quicker leads to a dull, burnishing feeling.

Let’s take a look under the optical microscope!

Optical micrographs of the Grain & Bond SG F120 (first/left picture) and SG F220 (second/right picture) stone. Instrument: Marvscope

The bright blue colour comes through very nicely in the optical microscope images. On the F120 size, we can make out the individual grains very easily. The are elongated, smooth and flat ones. The finer F220 stone meanwhile shows a few more white grains, as well as smaller, more blocky and square abrasive grains.

Let’s take a closer look in the SEM, first for the SG F120:

SEM micrographs of the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560.

The stones shows a large number of grains. They are a mix of flat, elongated grains and some blocky ones with multiple, ragged cutting edges visible. The overall concentration is quite high. Between the grains, we can see a grumbly, very small and dense binder. Some controlled and evenly distributed porosity is visible in the stone, which is a good sign on such a large grit – this gives some space for lubrication and swarf!

Let’s look at the chemical composition! For this we are going to use an advanced SEM technique called EDS. If you want to know more about this, I’ve written extensively about SEM microanalysis here on this blog.

EDS analysis of the Grain & Bond SG F120 stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The EDS analysis shows a large concentration of AO as abrasive in this stone, with some minor, very small SiC distributed on the surface – I would guess, probably from the manufacturing process. The binder mostly shows carbon – which to me makes this a resin stone? It has a surprising hardness, more on this later.

Next, let us take a closer look at the F220 stone:

SEM micrographs of the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560.

The finer stone shows a high conecntration of grains. They are a bit flatter, and oriented in a random way across the surface. Size is spot on, and it has a very homogeneous distribution.

Let’s take a quick look at the EDS:

EDS analysis of the Grain & Bond SG F220 stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

A bit more trace particles – we can find some magnesium, some sodium and some more silicon. Not quite as pure as the F120 stone, but at the same time: they are in a size where the AO abrasive still dominates the result.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. I am using a standardised testing procedure, read about it here. Nevertheless, it’s 65 HRC M398, and sharpened to 17 DPS with resin bond diamond stones down to 10 µm. Afterwards, the tested stone is used, first in a back and forth movement until the surface becomes homogenous, and then alternating, edge trailing strokes (5-5-3-2) on each side, for a total of 20 strokes towards the apex per side. No pressure is applied but the weight of the apparatus. Moreover, the same approach is repeated with a blade in NitroV at 59-60 HRC.

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

First, let’s take a look at the F120 (120 µm) SG stone:

Let’s start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560

Most AO and natural stones struggle a lot with the M398 I use for my reviews. While sharpening the blade for the analytics, I was quite surprised by the amount of black swarf that was created – but also by the delicate, fine apex. Typically, on non-superabrasive stones, these blades maybe get burnished, but the apex is dulled and rounded over. The SG can’t compete with diamond in this steel – but it leaves all other AO stones I’ve had on this blog far, far behind. I’d say the result is even better than comparable sized chinese OEM diamond resin stones, which is…wild.

THe morphology shows large, burnished sections, but also some clear cutting action near the apex. A couple deeper scratches and a slight waviness, giving a toothy edge can be made out and are of course also reflected in the optical micrograph:

Optical micrograph of the M398 bevel finished with the Grain & Bond SG F120 stone. Instrument: Marvscope

Which is further visible in the white light interferometer measurements of the bevel: a smoothed over surface, with a couple of deeper scratches.

3D surface height map of the M398 Bevel finished with the Grain & Bond SG F120 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

The surface roughness is exceptional for a 120 µm sized stone:

Sa	0.1752	µm
Sq	0.2636	µm
Ssk	-1.605	–
Sku	7.810	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edgefinished with the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560

The softer steel is, quite expected, a much better target for the SG stone. We get a very fine apex for this grit size, with a regular appearance and morphology.

Optical micrograph of the NitroV bevel finished with the Grain & Bond SG F120 stone.. Instrument: Marvscope

The optical micrograph shows a super smooth, regular bevel with some toothiness to the cutting edge. It is very pleasing, a matte, regular and homogeneous result!

3D surface height map of the NitroV Bevel finished with the Grain & Bond SG F120 stone.. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With the surface roughness parameters being a bit lower compared to the M398 steel:

Sa	0.1205	µm
Sq	0.1649	µm
Ssk	-1.209	–
Sku	5.458	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Next, we’re going to look at the results of the F220 (63 µm) SG stone:

Let’s start again with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560

The stone improved the surface finish noticeably. The bevel still has some deeper scratches, but overall it is very smooth already.

Optical micrograph of the M398 bevel finished with the Grain & Bond SG F220 stone. Instrument: Marvscope

The optical micrograph shows this in the form of very little contrast – besides the deeper scratches.

3D surface height map of the M398 Bevel finished with the Grain & Bond SG F220 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

Which also is reflected in improved surface parameters:

Sa	0.1498	µm
Sq	0.2226	µm
Ssk	-1.34	–
Sku	7.385	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edge finished with the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560

The difference is not quite as stark as it is with the M398 steel, but some refinement can be made out. Moreover, a higher amount of cutting traces instead of burnishing can identified. The apex is further refined – this was already quite the sharp knife!

Optical micrograph of the NitroV bevel finished with the Grain & Bond SG F220 stone. Instrument: Marvscope

The optical appearance of the bevel is a lovely, matte and diffuse, very regular scratch pattern – also exceptionally regular under the WLI:

3D surface height map of the NitroV Bevel finished with the Grain & Bond SG F220 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With quite low surface roughness parameters – keep in mind this is a 63 µm sized stone!

Sa	0.1170	µm
Sq	0.1574	µm
Ssk	-1.113	–
Sku	5.905	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

The stone itself has a high & wonderful feedback. I’m very much reminded of a Shapton Glass, which (up until this stone!) has been a favourite of mine. The stone pics up speed after a couple of strokes, with some slush being created and accelerating the sharpening action. From time to time, a larger grain comes loose – this can be felt and probably explains the deeper scratches. I found that during the couple of hours I spend with this stone, that the speed stayed identical. The typical glazing over that AO stones experience did not happen on this.

I would classify the binder as resin, based on the chemical composition visible in the EDS, even though it is unbelievably hard. I think this is probably the hardest resin stone I ever had on the blog – and this just screams at the manufacturer that there should be a benchstone coming soon, for the freehanders.

The results speak for themselves – a surface finish, factors better than I would imagine an Al2O3 stone could produce. Still working in what is widely considered a difficult super steel. Sharp edges. Wonderful feedback. Good lifetime. Available in 1×6″ format. Affordable price.This stone, to me personally is the “Shapton killer”.

There is very little that could be improved – and so I can only advise you to buy these, with no idea how you would get about doing this outside Russia. Let’s hope they arrive on our markets soon!

I can only end this review by taking my hat off to Alexander Likhovtsov – Моё почтение! Шедевр!

What a wonderful stone. I love it.