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Coticules are a relatively popular finishing stone from the Ardennes region in Belgium. Historically, they’ve been more popular as a multi-use stone in continental Europe (finishing tools, razors, knives, etc), but most of the references that I see in catalogs in the US are for branded razor hones. That is, those sold here before hobbyists became the main buyers of everything were sold as fine graded razor hones, often fairly small. Pike and Carborundum come to mind – I’m not a huge collector of them and only have a couple, so the list of US distributors branding coticule razor hones is probably pretty long.

The advent of shaving forums brought interest back for these stones. They’re overpriced for what they are in my opinion, but so is just about everything used for shaving. Despite the nostalgic mention here and there of someone recalling a Dutch woodworker they knew, I’d also put coticules at the bottom of any list of natural stones to try for woodworking. At one point, there were at least 7 different mines bringing out coticule material, and generally at the seam where the cream colored abrasive meets a blue stone layer. The blue stone also hones, but it’s generally not present on modern-mined hones. The tell for a stone you’re looking at is whether or not you can see a layer of glue, even if the dark backing is scuffed or dusty and not discernible. The natural blue stone when wet and smooth often has a bluish or purplish tone and markings that look like peacock feathers.

There are also glued stones older in age with a blue stone (abrasive natural) backing instead of slate. The reason the stones are cut at the seam is probably two-fold, but at least one is that the yellow abrasive layer by itself is unstable and can crack, and age isn’t a guarantee that the stone won’t crack as I had a natural combination “Old Rock” labeled that hadn’t been used, and over the 6 or 8 years I had it, visible cracks started to form. Cracking makes the stones harder to resell.

To my knowledge, only Ardennes is mining and cutting coticule hones, and the stones vary a lot in cutting speed, feel and fineness. A relatively small glued hone is generally about $100, and the sky is the limit above that. Anyone buying an 8×3 glued stone for $400 or more will be disappointed unless their objective is to use a coticule no matter what. Unless there is a secret somewhere, the typical customer for an ardennes hone is a straight razor user.

That said, it’s possible to get one that is very good and that creates a comfortable shaving razor, and it’s also the case that an experienced shaver is rarely going to hone (the linen and leather will stretch an edge for a year without much degradation – a good linen and leather, that is – and an experienced shaver will not do much honing, and certainly not the heavy handed honing we do for woodworking tools to remove wear. A properly maintained razor doesn’t wear much and the honing just keeps the bevel and apex from getting fat).

The abrasive in coticules is apparently garnet or something similar, and the abrasive is sort of tubby and round as opposed to disc shaped or more pointed like alumina will often be. That means that you can’t judge much by particle size (coticule abrasive particles are generally fairly large and not the more typical 3 microns or so that most fine natural abrasives land near).

Long story short, if you go out and buy 10 coticules hoping for 8 wonderful users, you’ve been warned. If you buy large older stones, there’s a fair chance you’ll get sandstone that looks like coticule, or a hard coarse actual coticule that was never intended for finishing (these are no longer marketed).

Typical use honing with a coticule is like a slurried arkansas stone. With slurry, the stones will be faster, but there will be something referred to as slurry dulling (the rolling particles will round the edge somewhat and leave it a little bit uneven).

While I’ve probably had more than 10 coticules, I have two right now, and that brings to mind a third very thin yellow layer stone, so I guess that makes three (thin yellow layer meaning someone used most of the preferred yellow side – it’s an older stone with a blue stone backing, and only a very very thin layer is left – it was cheap).

Of the large group of stones, I had one natural combination stone that was large and that did a nice job polishing an edge and had good cutting power. Every single stone I’ve had is markedly different in feel and speed, though. That stone was expensive and when I leveled with myself about it not really being better than any other typical stone (for example, a black arkansas still results in a sharper razor), I resold it fearing the fad would go away if the razor forums lost traffic.

I’ve kept one bout #10 (an odd shaped stone about double the area of a deck of playing cards) and then a really fine slow coticule that hardly cuts. The pictures below are from these two.

Compare this Picture to the 8,000 Grit Waterstone

First, the coarse coticule

And the edge of the same iron off of the finer of the two

At this point, there may be a person or two who mostly shaves or maybe someone who uses coticules as a finisher for woodworking. As with all stones, of course, you can use them for woodworking, and of course they’re suitable for straight razors. Part of the interest in sharpening stones is all of them work. If I chanced across a large coticule at a flea market for a reasonable price, I’d probably buy it and plan to just unload it when the thrill wore off. The lukewarm thoughts about this type of stone aren’t whether or not it can be made to work just fine, but rather whether or not it makes sense when there are better options that cost less.

Looking elsewhere will also save you from the strange fascination with giving different layers names, much like the “in the club” kind of thing with japanese natural stones where the true users of the stones don’t care that much what the name of the stone is, they care how it feels and works. If you are on a woodworking forum or a shaving forum, someone extremely enthusiastic about arbitrary titles will be correcting you when you’re trying to convey from a sense of doing. They’ll tell you that “you have to learn what you’re talking about” with the various layers and labels before you can talk about your own stones or ask questions – you can ignore that stuff.

The one thing these stones do have in their favor, especially if you manage to find an older natural combination with a label on – and you manage to luck into such a thing where it’s being sold for a song. They’re pretty, both the yellow layer and the natural blue layer when the blue has a lot of birdseye-ish pattern.

Same idea as the prior posts examining whether 1 micron diamonds improve the sharpening (for the user, not the tool) and resulting edge on a black arkansas stone. In that case, I think 1 micron diamonds do improve the outcome, and though I didn’t go up the ladder in more complex steels, but the diamonds probably make the oilstones more capable of dealing with those (where complex means microstructure full of carbides that are harder than the oilstone). It does seem to be the case, though, that on wood or well machined cast iron, the resulting edge with 1 micron diamonds is still better, so maybe it boils down to whether or not you like the feel of the stone better than either of those. I do.

But, what about more coarse stones? First, if you need to go very coarse with oilstones, or even to something similar to a 1k water or broken in diamond stone, a well-used india stone is a good idea. A stone like a soft arkansas or washita will easily follow and set up an edge that is short work on the finish step.

So, that leaves me to define more coarse as something like a washita or a “smith’s hard” which looks kind of like and feels kind of like a washita, but doesn’t seem to have the same cutting power. I have one of these that came in a box for $10 on ebay. If they climb too much past that in price, they’re forgettable. I found the same with 2.5 micron diamonds on cast iron -the edge isn’t that great for the fineness and I can’t think of a reason to use them unless they’re dropped on wood until the fun of that wears off (autosol is easier to use in that situation).

So, figuring I had two forgettable sharpening media, I put the 2.5 micron diamonds on the smiths hard and charged right in. Which negates the ability to take “before”. Luckily, I have some on file from prior tests – so this isn’t a great comparison in terms of same item, same time, but it’ll do.

Here’s the result of the “Smith’s Hard” on a plain carbon steel iron that’s not terribly hard.

You may start to notice a theme – the visual differences between finishing stones aren’t that great. In this case, the edge is very even, and the result is better than one would expect. I think this is helped (this positive result) by the fact that the stone is a bit slow. If you have harder steel, the result is finer yet, but it’s also the case that this middle stone needs help before it on harder steel. As in, if you have much work to do with the stone, the slow speed gets annoying and it goes back in a drawer, replaced by a washita which does the same thing but cuts faster.

Following that with a perhaps-too-generous charge yeseterday while using a paring chisel (for real work, no less – paring the back side of a guitar neck heel), this is what the microscope reveals.

Once again, we have two unlike pictures and it’s difficult to look at the two and know which edge is better. Well, just from using the tools, the edge shown in the second picture is a lot sharper. Paring hard maple to fit a neck heel to a guitar body was extremely pleasant (paring hard maple in some thickness beyond that, not always so pleasant).

Is it an improvement? Definitely. Is it better than anything else? I don’t know – what stands out to me for ease is still autosol on wood. It’s difficult to beat in terms of creating a sharp and durable edge.

From sharpening, the diamonds do create sort of a rolling slurry/sludge on the stone even though they’re just dry diamonds. I don’t know if this is all metal swarf mixed with WD-40 or if it’s also stone particles. But it’s fairly obvious from the picture, the cutting mechanism isn’t the same – the matte type finish is more indicative of some rolling/moving particles vs. abrasive staying in place. If the sludge gets to be a bit much, then a drop or two of WD40 allows it to move again. It’s not, by any means, fast compared to diamonds in cast but the edge is surprisingly excellent from two bits of sharpening material that don’t seem that great on their own.

Since I have them on hand – here are two pictures of the stone box and the stone. Note that it looks relatively fine (it is, and so are some other soft arkansas stones). This stone is not, however, similar to a Norton or Dan’s Black or Translucent arkansas stone. Smiths is a name that’s still printed on stones. I can’t comment on the stones beyond saying that they appear to be a little bit less fine now and I have no clue whether the company has been bought and sold or doesn’t exist and it’s just the brand name.

Smith’s Hard – Not an 1800s stone, but not a new stone, either. Finishes about as finely as a good washita stone, but is only half as fast or less.

Some years ago, I heard about Garrett Hack charging oilstones with fine diamonds. But, I didn’t hear it from Garrett. I heard it from someone who disapproved of it and was sure that it would result in less fine edges.

When doing the “sharpening omnibus” the first time, I found that lightly abrading a broken in translucent arkansas stone didn’t result in the decline in edge quality that I expected. As in “making a slurry”. So, I’d forgotten about diamonds in fine natural stones (not friable ones, but hard ones -why bother putting diamonds on a stone that self slurries – they’ll be gone quickly) until then. Previous tests (for me) of diamond grit found that there’s no real benefit to using diamonds to finish something unless they’re really fine. As in, I tried 5 micron and 3 micron diamonds to see if there would be a fast but fine medium where someone (including me) could grind and use one honing grit and that’s it. It didn’t work out well – a 3 or 5 micron diamond edge is coarse unless the diamond is on a soft substrate. I never tried it on pine, but maybe it would work. The reason that I didn’t try it is simple – 1 micron diamond doesn’t cost any more and it works finely on anything.

How finely? it outlasts any natural stone that I have (and I’ve had hundreds) in planing edge life. Not enormous amounts, but measurable, and the initial sharpness is greater. You can be as good as you want to be with natural stones, but you cannot practically make them match smaller oxides and diamonds if you’re just chasing the limit.

After doing the slurry test mentioned above, I lost my vial of 1 micron diamonds and until this week, never got another one.

Now that I have 1 micron loose diamond (which costs all of $8 shipped on ebay), I figured I’d give them a whirl on arkansas stones – knowing that I have zero interest in using coarser diamonds.

The test subject in this case is a Buck Brothers socket chisel – but an old one and one that’s harder than Buck Bros Cast steel tools typically were. Subjectively, it’s about like better old English tools, and comparable to the best O1 tools you’ll find (like iles bench chisels).

First picture – Dan’s Black and 20 seconds of work and then hone the bevel. No stropping is done in this case, and no buffing (the buffer would run enough off of the edge of this that the disturbance at the edge would disappear in favor of a perfect line – it’s good for that, but it makes comparing the stones themselves a little harder). No diamonds are used for this edge.

Dan black Only – 150X – nice uniform bevel

It’s possible to use an oilstone and finish an edge better than this, but the reality is it will take successive sharpening and a lot of care. Since this is a hard chisel, the stria are close together and small, and despite not stropping, there’s little disturbance at the edge. When this is done in the next blog post, I’ll work back around to refinishing this edge with the black stone again just in case the little spots are minor pits (very minor). A black arkansas is a slow stone, so the practical part is you can use a lighter and lighter touch quickly, but to use it to get a much brighter polish would take minutes just on the back of a tool at each sharpening session. Practical is to apply directed pressure and then lighten that pressure.

Second picture – same stone, same edge, but after sprinkling 1 micron diamonds on the stone and adding a drop of WD40. This created a slurry, but the more dry stone (less oil and not a puddle is nice with fine arkansas stones) acted as a brake with the diamonds and literally kept from being able to move it.

I noticed two things after 20 seconds of work – there was no grip on the stone with WD40, so something between nothing and what I had may be nicer. But second to that, no wire edge formed when honing the bevel on the opposite side. A black arkansas stone will form the finest of burrs, but you can still feel it if you don’t work it off of the tool or strop it off. It’s not there with the diamonds.

Same as picture 1, but 20 seconds of work on the back of the tool with 1 micron diamonds on the oilstone. A small improvement

How much of a difference does this make? Visually not enough to conclude anything. Less lubricant would’ve made it a little easier to get the diamonds to bite.

Third picture : so, I went back for another 20 seconds hoping to see if I could hone off any disturbance at the edge.

20 more seconds of back work and more refresh of the bevel – 40 seconds total of polishing on a fine black stone with 1 micron diamonds loose on the surface.

Some actual testing of the edge in something comparable is probably needed to really be able to tell if it’s an improvement beyond just different visually.

Again, no wire edge.

My head is full of thoughts or questions about what’s happening with 3 micron natural particles fixed in place and 1 micron sharp particles moving around. I can’t see any evidence that edges are degraded (no surprise). But before using no diamonds: Fourth Picture – one more shot with the slurry dried off a bit so that it’s stronger cutting.

This suggests that the tip of the tool above just wasn’t yet honed off (either from the back, or more realistically, by shortening of the chisel with successive honing).

The lack of any real burr is kind of a treat. That suggests that if you’re using a two stone regimen, you can eliminate teasing the edge off or stropping. Will that last forever without a fresh slurry of diamonds? I don’t know. That’s maybe beyond my scope here. Next item for me is to see if the diamonds that come from china in 100 carat lots for the same price as 25 from the US ($8 or so) are equal in quality.

While these pictures all look different, I can’t say definitively any of the above differ much – none looks like a laser cut edge, but all are very good quality edges suitable for anything, and super uniformity can be had with very light buffing if needed, or removing any remaining burr with autosol on wood. I will make a note for myself to do this same treatment to a plane iron – ark only, ark and diamond and then ark and autosol – and see if anything creates a drastically finer smoother shaving.

It’s worth going back now and honing this chisel on the arkansas stone only now that any initial anomalies should be honed out (be they lagging minor corrosion or whatever else, so here’s Picture 5 – honing again on a section of the stone that has no diamond (luckily, this is a 3×10 stone so there’s fresh space remaining).

…….

later add: I was interrupted just as I was about to post this blog entry, and the interruption made me think. Maybe I should compare diamonds as I do have a high quality cast plate (recall prior posts that if you just try to turn a plane bottom over and use it, especially if you have to abrade it, you’re not going to get ideal results).

So, Picture 6 – diamonds on cast. In this case, there’s a load of diamonds on the surface and if allowed to embed in the cast, the cutting speed would slow some over time before refreshing is needed, but this cut will also get finer (as in, this should get closer and closer to uniform polish). This plate has been sitting for over two years, so there could be all kinds of things on it that I don’t know about that are leaving deeper scratches (Dirt, little rust particles, etc) – who knows.

I’m not sure we learned anything I hoped we would, but the pictures do make it clear that if you’re sharpening to this level of fineness, you can’t damage edges and expected the fine abrasives to recover them.

Long in the past, a vendor of sharpening good sent me a tube of dursol. For purposes of this article, you should consider it the same as autosol. Why? Because, for sharpening, it’s the same other than smell. I didn’t have autosol handy at the time that I did this comparison a couple of years ago, and didn’t consider that many would follow with “how does this compare to autosol?”.

That aside, another thing that I think many fail to grasp is when you’re comparing micron sizes, etc, you’re seeing an incomplete picture – the complete picture is the agressiveness of the abrasive and then how aggressive the substrate allows th abrasive to be. Autosol or Dursol will cut as finely as almost anything else when they’re used on wood or MDF. The substrate is soft enough that the particles stick in it and then they  rub the steel. Quite effectively. The other nice side benefit is that when they do, if there’s a foreign spec of dust, it also gets pushed into the wood and won’t automatically notch an edge (but sometimes it does).

Autosol and Dursol are, to the best of my knowledge, about 3 microns and made of an alumina type that’s more like flat discs, so they’re not 3 micron round balls. But the alumina is hard and I’m not sure it fits the desire to make it out like it works finely because it breaks down (plenty of abrasives that are described as breaking into little pieces don’t actually do that).

When used on wood, the action of Dursol or Autosol is lovely. When used on cast, it’s aggressive, but only a little faster. What’s the virtue of cast iron? It’s not universally useful for honing with things like alumina. It’s wonderful with very fine diamonds (like 1 micron or finer). But it’s not good for finishing edges unless abrasives are very small and strong cutting at the same time. It’s also very unforgiving with settled dust or particles (you’ll hear the noise as those notch edges and cause you to go back a step in your sharpening routine).

If you have an interest in using cast iron with small diamonds, then you’ll want cast that’s ground finely, and not just a spare plane sole, but that’s a different subject. I’ve tried both, and a self-made plane sole will generally have abraded ridges (that prevent uniform fine edge finish) while a blanchard ground piece of cast will be relatively smooth, and in a hone sized piece, likely much flatter.

Back to the subject of this blog – pictures of edges prepared with Dursol on cast iron first, and then Dursol on pine. White pine is a bit soft, but the pictures look the same with medium hardwood and harder softwoods (like dry yellow pine).

Dursol on Cast Iron

Compare this Picture to the 8,000 Grit Waterstone

Dursol on Pine

Dursol used on Pine: The abrasive is still reasonably fast (and to get a finish this could, should follow something finer than a typical 1000 grit stone – like a washita stone or a 4000 grit or finer waterstone)

There’s one use consideration – once your edges are relatively sharp, they’ll cut wood, so you’re using the iron on wood flat or dragging, but you can see there’s no burr left behind on wood. On cast, you can do whatever you want – the risk is damaging the edge with rough handling, not damaging the cast.

If you’re curious about the level of finish from 1 micron diamonds on cast vs. the dursol on pine, i can’t find a functional difference – unless you’re using steel with a lot of vanadium, and then there’s no reason to use media other than diamonds for any part of the honing process.

I made this post because fine sharpening isn’t expensive, and Autosol and Dursol aren’t the only way to get these results. Buffing bars with a drop of oil for lubricant will do the same thing when you scribble their composition onto wood.

What often comes after I make the recommendation of one of these polishes on soft or medium hardwoods, though, is: “Can I do ___ instead?” (use the polishes on leather, brass, aluminum, cast – whatever it may be). Most of us have offcuts of wood, and if we don’t – that’s a little odd. The desire to take a suggestion and do something different immediately is kind of annoying, though, but it’s the internet.

All that said, seeing the difference in results above isn’t just a comment to avoid cast with alumina. That’s probably not universally true, either – it’s understanding that the substrate makes a difference, just as abrasive type and size makes a difference. If you have something fast (like the gold bar that works well with unicorn), maybe it’s not so great on a hard surface, but would provide a great combination of fast and fine on a scrap of wood (in fact, it does).

One more for the natural stones. This is a dark green hard but strong cutting and fine Japanese natural stone that I got off of Buyee (proxy service that allows you to bid on Japan’s version of Ebay).

I’ve bought a lot of stones, and I’ve sold stones (but only on a break-even basis). The reason for the metallurgical scope in the first place was to resell an abundance of straight razors that I’d accumulate and sort and honestly grade stones. This green stone is really one of the very few “something for nothing” stories, as it’s a near full size stone that’s either nakayama or narutaki mine (but the characteristics match that of nakayama – a hard fine but strong cutting stone that’s very strong on slurry despite not being coarse – on water with no slurry, the stone is a bit harsh feeling. The bottom line is that this is as good of a stone as you will find for a japanese finish stone of the fine and hard nature, and better than a hatanaka stamped stone that I also had (though hatanaka stamps until recently were always uncommonly uniform and aesthetically interesting – I looked on buyee now years removed from selling stones and see that the hatanaka stamp is now being forged as it was present on misshapen and common stones. That’s too bad).

I think the myth about japanese stones being “30k” grit equivalent is finally not the norm when their fineness is discussed. They are similar to the best of the trans or black arkansas stones, but with a little better fineness and stronger cutting power on harder steels (japanese natural stones from the mountain with the best mines are between 15-20% natural aluminum oxide from volcanic ash. If you’re the grouchy western type that thinks that’s mysticism, that’s tough – they do actually have aluminum oxide in them, but not in the same concentration that something like a shapton stone would – it’s mixed in with SiO2 (which itself is in the neighborhood of another 60% of the stone matrix).

So, what was the win? This was an “unmarked” stone sold by someone who picked barber shops and after flaking some of the crud off of the end of this stone, it has a very old stamp that more or less just says “original whetstone” or something of that sort (The kanji isn’t on the stone in 6 places with bright new purple ink and it doesn’t say “nakayama super best gaijin magnet” or anything like that, it just clarifies that it’s from the original mountain and that it’s got its bona fides. This was $32 plus proxy and shipping fees. But no worries, I’ve had plenty of $400 stones that really were $250 stones and when I did finally sell this one, I sold it for less than half of what it should probably have been sold for. You can’t keep everything And I still have somewhere around a dozen japanese finish stones.

I’ve had around 200 japanese natural stones in total. Very few feel the same if you’ve seen enough to start differentiating them. I’ve not had a large stone that was quite as good as this one at what this one is good at (hard, releasing no slurry, but with a fine biting slurry that’s very practical if the slurry is kept).

A picture of what this stone does both on slurry and then on clear water is below. If the objective was to get this picture to near optical clarity, then the stone must be allowed to dry while the honing process continues.

Compare this Picture to the 8,000 Grit Waterstone

The surface of the older stone – a little dry swarf left on top. Many stones have this color of green, but the really good stones are usable and make things sharp. The same appearance is common from a modern lower quality stone that may scuff on the surface and release a clump of particles.

I cannot recommend buying japanese stones for no reason, unfortunately. I don’t think you get what you pay for from dealers, and on average, the new stones are not a match for picker-sold old stones (but the latter is the kind of thing where you buy 10, keep the two you like most, sell 6 and throw away the two that broke or delaminated either before or after you buy them).

What you find on proxy services is a good reminder that people in Japan don’t necessarily think the stones are worth as much as we do aside for some uncommon stones with rare characteristics. And you won’t guess what those are when you’re new, so you’re far more likely to overpay (at one point, I purchased a large atagoyama stone off of the proxy service from a hardware store – i.e., retail – in japan. $235. I saw the same stone, same stamp, same size on a continental european “japanese stone specialist” site for $900. What do you get for the difference? nothing – atagoyama is one of the few mines that had stones in such abundance that the stones were consistent in appearance and cutting properties after they were separate by grade.

Ultimately, if you have tools that can be sharpened by a high quality black arkansas or translucent stone, how much better is the resulting edge from a japanese natural stone? It’s not, it’s about the same. In fact, the best of the natural fine stones all land around the same place.

One more for the sharpening stone omnibus. The Dan’s Black arkansas, and a first quality one at that. Dan’s has the finest black stones I’ve ever seen. They’re not the fastest cutting, which is the way the rules work generally with good arkansas stones. In my book, a good washita does the step just below this well and faster than any “normal” oilstone that’s not a true washita, so I don’t have any soft spot for an arkansas finishing stone that’s a little coarse. They will all break in, but a fine one will continue to be fine even if you scuff it a little.

You can also consider the results of this to be identical to a translucent stone (I’ve had at least a dozen trans stones of decent quality). I’ve also had black stones from Halls, which I believe may be Preyda now – they are decent, but not quite as good as a first quality Dan’s and sticking with Halls, as that’s what I recall their label, the fineness was a bit less and on the ones I tried, a stray clump here or there could come out of the stone. I’ve not had that happen with Dan’s.

Translucent stones that pass light well are a safer bet – the lack of air space to allow light through that easily is hard to fake on a translucent and the only risk is whether someone may be selling you an entirely different stone. If a translucent stone only barely passes light, though, you may be in for something with more cutting power than you expect.

Arkansas stones leave a flatter groove, but are very sensitive to steel hardness. Their particles fight an even battle with 62 hardness iron carbides or steel matrix, or however you’d gauge it. Much lower than that (like a soft pocket knife) and even the stone used for this picture will raise a strong burr. If you run into that, light strokes to thin the wire edge and then go to a compound.

Compare this Picture to the 8,000 Grit Waterstone

It takes some time and skill to get to this finish level whereas the autosol picture, you just need to not have nicks beforehand. I think the day to day use of a trans or black arkansas stone for chisels and planes is more work than the results yield. Why? The washita cuts faster and nearly as fine, and as bloated as they have gotten in price, they’re still less cost (push the lilywhite aside) than a good translucent or black arkasnsas. And once you finish with the washita, have raised a burr and teased it off, a couple of swipes on softwood or medium hardwood with autosol or something similar and the edge is finer than the arkansas stone can create.

Back to the Dan’s black. 2x8x1 is my suggestion, but they’re expensive. It’s a lifetime stone if you don’t drop it. If the price is just too step, find a first quality dan’s combination with a soft stone for one half of the thickness and the subject stone here for the other half. The feel will be the same and 10 workmen would never go through half an inch of black arkansas stone in a lifetime. It’s just easier to use these stones when they’re raised in a case.

Which leads to one more point (aside from one more reminder that these will reward skill and you may have difficulty at first with them) – keep your stones in a case or covered. With the high hardness, one stray piece of anything lands on one of these and the first pull or push across it and you’ll have a tiny notch in your iron.

How long does a stone like this last planing when you take the time to finish the edge as above? about 85% of the footage planed that 1 micron diamond will yield. Yes, I know. It’s not the result that I wanted, either, but the discussion of properties changed in steel and the (other) unicorn to be chased at the edge to find miles and miles of planing beyond just finishing the edge, it’s not there.

But, these are nice stones and they do come into their own with really small tools and crisp corner carving tools.

One more thing (Columbo?) – if you bring a damaged edge to this stone, you won’t ever finish it. You can vary pressure and get different results, but if you lean on a tool too hard, you can actually create small chips along the edge. Firm to light pressure – but keep your feet on the floor. And – they’re not great stones for someone who uses a guide. All Arkansas stones reward touch. When you’re using a guide, you’ve mostly lost the ability to do that. Your skill comes in getting this stone only to work the tip of the tool. This skill is enormously aided by spending $15 for a very small USB hand scope (as in, hand held microscope) so you can see what you’re doing.

I tested plane irons 2 years ago to examine edge life claims. At the time, I also did some extra tests with different finishing stones, methods to see how much extra life is imparted to an edge with finer abrasives. It turns out to be relatively substantial, but also in planing effort – sharper is a large difference in effort keeping a plane in a cut, starting a cut, and in total feet planed). The test was actually a duration test, so I planed somewhere around 30,000 – 40,000 feet as controlled as is possible. The later posted CATRA testing on knifesteelnerds finds ratios much the same as I found.

Because some of the planing was with irons that have vanadium carbides, I used diamonds as the sharpening media. 1 micron diamonds was my practical finishing step – first on hardwood, then on a wonderful cast plate that someone provided along with the test. A cast or steel plate with such fine media needs to be really good – just attempting to flatten a plane sole and use it will not work – the texture on the sole will damage the edge somewhat during use and until you manage to wear the sole to a high finish, it’ll actually raise a burr.

Very few steels will raise a burr on 1 micron diamonds.

It turns out, they will also create an edge that outlasts any stone that I have (15-20% more edge life), but much like the discussions of the true applicability of the tests, in heavy work, you won’t be able to see that gain – only if you are planing continuous clean wood.

So, I haven’t really made any “official” classifications, but I’d call an 8k stone the fine standard, and the 1 micron diamonds, the standard for extra fine (and autosol on wood is surprisingly good at that).

Great edge uniformity – even if a little tooth around the turn, the apex is crisp and wear under normal conditions is uniform (there is no unusual damage that occurs due to the edge being sharpened by diamonds, though diamonds 3 microns or larger do start to result in poorer edge life).

My apologies for the different looking image. Windows versions (changing computers) forced an expensive turret camera replacement and this picture was taken just before the prior PC gave up the ghost. Same magnification, though, and same length of edge shown in the picture.

The one nice thing about very small diamonds is that they will leave a very fine edge on anything, including steels not hard enough to hold it. Natural stones, on the other hand, have much larger particles and steel hardness will go far in determining how fine the actual edge is. The harder the steel, the slower they cut and the finer the edge. Diamonds are like a disposable camera – you just use them.

Typical Price at time of posting (2021): $10 for a vial of dry lapidary grit. Avoid pastes or woodworking suppliers for diamonds – you don’t get much volume compared to buying vials or bags of lapidary grit. Use with any lubricant (a thin oil is nice, WD-40 is fine). Just the same, avoid any “Formulated diamond lapping fluids”. Most specialty fluids targeted at amateur woodworkers are nothing more than hydrocarbons bottled in little bottles and marked up horribly.

So, if they work better (by edge life, and by sharpness), why don’t I use them? I just don’t love the feel of a cast plate, but its effectiveness can’t be denied. A heavy hand on a cast plate can also cause small nicking in the edge (too much pressure), and if there’s any ambient dirt on something like cast, it will notch the edge on the tool you’re sharpening.

First to be shown in the “omnibus” is the typical 8000 grit waterstone finish. This sentiment is now out of date, but when I started woodworking, nearly everyone used waterstones in the hobbyist world and a king progression finishing at 8,000 grit or something similar was a standard paint-by-number suggestion.

I would suggest unless you’re really new and progressive and these types of stones aren’t something you’ve seen, this is your standard to compare other finish stones to. There are finer, and there are more coarse, but there’s nothing in hobby woodworking that this won’t cover.

This stone is the “kitayama” stone sold by imanishi. It’s very inexpensive in japan, sometimes marked up here.

Edge uniformity is decent, but the slurry makes the edge itself a bit toothy.

The stone with slurry dry – the markings on the surface will wear off, but I’ve since sold this stone. This stone works far better with slurry of its abrasive than just with clean water.

If you keep something to level the surface of this stone handy, it’s easy to use and wide for beginners using guides. It will gouge fairly easily, though, and is limited if you move to things like carving.

Typical Price at time of posting (2021): $60.

If you see this stone listed for much more than that, you probably ought to consider what else is marked up. Sometimes that’s an issue of distribution and not retailing, but retailers with prices near or above $100 for a stone like this are generally high on everything. I’d refer to those types of retailers as beginner’s traps – they have catalogues and lots of advertising, and are trawling a net to continuously find new customers.