Month: January 2022

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).