The Belgian hones (Coticule and Belgian Blue Whetstone, commonly abbreviated to BBW) are very closely related. They are mined together. Actually is is impossible to extract any Coticule without also extracting massive amounts of BBW. Traditionally, Coticules were always backed by a piece of BBW. Some bonded together by nature, but most of them glued together by man. The main reason for this is to reinforce the Coticule part with the stronger Blue stone. Nowadays, Coticules are backed with a piece of Portuguese Slate, because it is more cost-effective to use easily available slate tiles for backing a Coticule than to produce labor intensive backing stones out of BBW rocks. The BBW stones are now sold separately, because they posses honing qualities of their own. Both the Begian hones are used with “slurry” This is an abrasive milk raised on top of the hone by moistening the surface with water and rubbing it with a small piece of Coticule/BBW The slurry of the Belgian hones contains spessartine garnets. These garnets are extremely hard mono-crystals with a very typical shape.

They are hard enough to scratch steel. A slurry is not  made of garnets only. It also contains water (obviously), and a great deal of phyllosilicates. Phyllosilicates are minerals that are much softer than steel. These minerals bonded the garnets together before they were abraded off the stone by rubbing with the slurry stone.
On a hypothetical note, that explains what we have found in frequent observations, small garnets can easily sink in the steel. Larger garnets can’t sink so deep in the steel, because the honing pressure is spread out over a wider surface area. Try scratching a table with a spoon. Now try the same with a fork (Don’t send your wife or mother to me when you run into trouble over this important experiment;-)) Back to the garnets: with the size of the segments at the garnets’ surface being roughly the same, smaller garnets are less rounded than larger garnets. That makes smaller garnets more “spiky”.
Conclusion: large garnets leave slightly wider but also more shallow scratches, while small garnets cut more aggressively and deeper.

Coticules contain a high concentration of small garnets (5 to 15 micron in diameter): up to 40% of the entire volume of the rock.
BBWs contain a lower concentration of wider garnets (10 to 25 micron in diameter): up to 25% of the entire volume of the rock.

That makes BBW’s slower than Coticules and if we are aiming for serious steel removal during the first stages of honing, the average Coticule will perform a great deal faster than any BBW. Hence, if the choice to do serious bevel correction is between Coticule and BBW, pick the Coticule.

But there’s more to the picture:
The loose garnets in the slurry also abrade the very edge, while it plows through the fluid. The thicker the fluid, the higher the concentration of garnets (less water) and the more the thinnest part of the edge deteriorates from the impact with the garnets. That is a dulling action. At the same time, the garnets remove steel from the bevel sides, which is a sharpening action. As long as the edge is not very sharp earlier during the honing process, the dulling effect is negligible, because the tip is not as fragile. When the edge becomes sharper, the tip becomes more fragile and more prone to “slurry deterioration”. At a given point, there’s a limit where the edge looses as much keenness as it gains. You could hone the razor into oblivion and not ever get a sharper edge than this limit. One of the advantages is that you’ll never “overhone” a razor on a Belgian slurry, allegedly a common danger on synthetic water hones. With normal pressure and regular razor honing methods, we have never been able to see any evidence of “overhoning” on the Belgian hones.

At equal slurry thickness, a BBW with its lower concentration of less aggressive garnets, has a sharper limit than a Coticule.

Of course you could use thinner slurry on a Coticule, but for the inexperienced user it’s still easier getting more keenness of a BBW with slurry than hitting the same level on a Coticule with thinner slurry. With experience it can be done, however, and the BBW becomes pretty redundant for razor sharpening at that point.

When no slurry is used, but plain water instead, we get a different story. The garnets remain halfway or more embedded in the surface of the hone. A Coticule with its small garnets in higher concentration offers a very finely textured surface. The BBW, having more sparsely spread bigger garnets offers a less fine surface. Both hones become very slow. The BBW becomes so slow, that it seems to loose most of it’s honing qualities. It almost behaves like a piece of marble. It seems to very slowly dull the edge rather than sharpening it any further. That’s why it is not recommended to dilute the slurry to plain water on a BBW.
But Coticules just keeps on going, albeit at an extremely slow rate.

No slurry, no slurry deterioration either.

Obviously the edge won’t gain sharpness infinitely. As with any hone there still is a limit. That limit is defined by how deep the hone cuts in the steel. A hone that digs 0.5 micron into the steel will never define an edge thinner than those 0.5 micron. That’s one good reason to use minimal pressure during the final stages of honing. Coticules on water are slow. They remove almost no steel with each honing stroke. For that they can define very sharp edges. But they are so slow that it takes ages to catch up if you weren’t already at a very decent keenness when you decided to start working on water only.
A Coticule with water is a finishing hone. The majority of them can’t be used to make up for much neglected keenness earlier on in the honing process.

There are differences in Coticules, mainly in speed, and – correlating to that – the sharpness level you can manage to get from the hone when it’s used with slurry (an abrasive milk formed by a mixture of water and stone particles that are released by rubbing the surface with a smaller piece of Coticule). After the slurry stage, Coticules are always used with just water to refine the edge further and achieve the maximum keenness that can be reached. If done correctly that keenness will always be more than adequate for a smooth shave without any “pulling” discomfort.
During the slurry phase, faster Coticules level off on a less sharp limit than those who approach their goal at a slower pace. This happens because there is a higher concentration of abrasive garnets present in the slurry of fast Coticules and presumably they are also more aggressive. These garnets impact with the very tip of the edge, which causes it to loose some of its definition. The keener and fragile the edge becomes during the honing, the more it is affected by this process.
Slower Coticule display less off this behavior, and they generally do leave a sharper edge, coming right off the slurry stage.
But either way, slow or fast, the edge won’t be keen enough for a comfortable shave after honing on slurry. The slurry is just used to vastly speed up the first part of the honing. You always have to finish on plain water, preferably after some additional procedure to bridge the gap between the speed of slurry and the very slowly developing superior edge on plain water. There are several different options to pursue that, and they are presented in the razor honing articles found on www.Coticule.be
Most Coticules that abrade steel fast with slurry are also relatively fast with just water, so although they start with a handicap after the slurry stage, they are quite capable of catching up. Slow Coticules start with sharper results off the slurry, but they require more work to further refine the edge. Of course, there are not just two categories, but rather two ends of a universe, in which all Coticules are located. It must be clear by now, that every specimen of these natural whetstones asks for a slightly different approach and amount of work required to get the best results.

The answer is yes and no.

Till the second half of the previous century, Coticules have been mined at several different locations, all within the wider area of the Belgian town Vielsalm, by several mining companies. They all extracted raw Coticule rock from either one of 2 principle deposits, one extending from the village Regné all the way to the village Ottré, and another one extending from Salm-Château to the South of village Lierneux. There are a few additional, minor, deposits in the vicinity of the village Sart. The geological origin of all these Coticule deposits is the same. In spite of popular belief, the fomer mines were not abandoned because they were depleted, but because extracting the narrow Coticule layers is so labor-intensive that it eventually became no longer economically feasible in a shrinking market, with the laboring costs within a post-industrial country. It is in all fairness, not possible to assess the distinct properties of the hones produced by mining companies that closed long time ago. All the more because some wholesaling companies obtained Coticules from several mining companies and branded them with a large number of labels, sometimes marketed towards different user groups.

With the above in mind, the anwer is “yes”. There are vintage Coticules that come form layers that are currently not under exploitation, mined at locations that are long abandoned. Although it is not possible to identify them, “vintage” Coticule can be bought that originate from obsolete layers.

On the other hand, the answer is also “no”. From the currently mined layers, there is no single reason why the rock that is mined today would be any different from the rock that was mined 100 years ago. Coticule rock was formed approximately 480 000 000 years ago, a few 100 years more or less won’t make any difference. One could argue that “they picked the best rocks first”, but such an argument forgoes the fact that Coticule rock runs as thin layers almost vertically in the underground. Mining it is not a matter of grabbing what is best, but primarily a matter of what comes first and what is the easiest to extract.

Furthermore, elaborate comparison between a number of randomly obtained “vintage” Coticules and a large group of recently mined ones from all currently active layers, has not revealed any additional differences between “vintage” and “recent”, other than the variance found within the recent production. That variance is mainly a matter of abrasive speed. There are vintage Coticules as fast as the fastest recently mined Coticules, and that statement can also be made for the slowest Coticules in the spectrum. When it comes to edge finishing properties when the whetstones are used without raising an abrasive slurry, the differences between Coticules, both vintage and recently mined are too small to be quantifiable within any scientific bearing. Such assessments remain in the field of vague impressions, easily overruled by differences in the steel of the tool and other external factors that interfere with objective assessment.

The bottom line is that, unless you are a collector who esteems the historical value of a yesteryears whetstones, their labels and boxes, the word “vintage” is out of place. For sharpening practices, it is fair to speak about second-hand Coticules, and if you can buy them at a second-hand price, they are as good a deal as a recently mined one.

No. This is a myth, launched by people that don’t know how to use them. It’s easier to say that the fault is in the hone…
Coticules do take a different approach than synthetic water hones.Translating the methods for synthetic water hones to Coticules yields poor results.
During one of my visits at the quarry I have seen that sometimes (rarely) quartz inclusions can be present in the raw rocks. Should these inclusions be present in the hone, they would cause damage at the very edge. That’s why the people at Ardennes Coticule cut the hones out of quartz free chucks, and if they do spot a small speckle of quartz in a hone they would never let that one to pass for sale.

If money is an issue, opt for 150mm X 40mm, That’s wide enough for inexperienced fingers to keep the razor comfortably in touch with the hone, and long enough to perform a decent honing stroke. Anything more is a luxury, but the resulting edges will not be better.

No. It is a matter of preference. Just like you don’t really need a straight razor in order to get a clean shave, you don’t necessarily need a Coticule to sharpen a straight razor. There are many other options to put a great edge on a razor. But as straight razor shaving is the most artisan way to shave, we at Coticule.be feel that using a Coticule is the most artisan way to sharpen a razor. Coticules have a legacy that goes back to ancient Roman times. Some people find that appealing. Yet the shaving results of a Coticule edge can easily meet those obtained from modern high-tech synthetic hones and it remains one of the most skin friendly edges one can ever shave with.

Many synthetic hones tend to glaze rapidly with abraded metal debris, sticking to the surface. Regular cleaning is required, to reclaim the full performance of the hone. Coticules, however, do not glaze. They are non-porous and therefor metal particles have no recesses to stick on to.

Another reason for lapping whetstones, is to reinstate a trued flatness. Yet it is not necessary to be persnickety about such flatness. For the honing of straight razors, that need perfect edges, because no razor can bluff its way through a shave, tests did not reveal any advantage for a mathematical flatness over a trueness “at first sight”.  For chisels, gouges, and other tools that have a way of wearing a transverse hollowing into a hone (as opposed to longitudinal hollowing caused by sharpening razors and knives, lapping needs to be done at slightly higher frequency. The wear rate of a Coticule depends on its purpose: sharpening chisels being one of the more eroding tasks and sharpening razors the least eroding. If you adhere to a few habits to keep your hone flat within good reason, depending on its purpose of use, it may stay serviceable during its entire lifetime, or only rarely demand lapping. These habits are:

1. While raising slurry, spend extra time on the far ends, notably the corners of the hone. Secondly, concentrate on the “high” spots. They can be identified because you’ll feel less resistance rubbing over them. At the lower spots, the rubbing stone will suck itself to the hone.

2. If possible don’t use the hone in the same direction during the regular slurry stage of honing. Once you arrive at the “refining” stages, do keep the stone oriented in the same direction. (You don’t want slight variations introduced in you honing at that point)

Should the Coticule arrive at a state where the out-of-trueness affects the quality of the resulting edge, it is time to lap.

There are several viable options:

1. Lapping with a dedicated lapping plate and abrasive powder, usually carborundum.

2. Lapping with a diamond hone in the 100-400 grit range.
Rub the lapping hone and the Coticule together under a slow running tap.

3. Lapping with sandpaper (in between 100 and 400 grit) on a known flat surface.
This can be done dry or wet. For dry use, spray-glue the sandpaper to a flat surface, and rub with the Coticule over it. Brush the sandpaper clean regularly.
For wet use, stick moistened sandpaper to a slick surface and work under a slow running tap.

To control for flatness, draw a pencil grind on the surface of the Coticule and check if you can remove the entire grid with just a few lapping strokes.

Without being an expert in Chassidic Judaism, According to Orthodox Jewish Law, “impure” procedures are not allowed for the slaughtering of animals and the processing of meat. This means that Orthodox Jews are not allowed to use oil stones for the sharpening of the knives used for butchering practice, for oil may contain “impure” substances. Coticules that are harvested from deep within the Earth, are considered to be “pure”. “Kosher” means just that. In essence, every Coticule is a kosher one. Jewish law also prescribes that the animals must be killed with one cut. That calls for sharp knives and Coticules have always been acknowledged for yielding extremely sharp edges. Allegedly, the knives are stroked over the whetstone quite often – every few cuts -. This gets blood on the stone, which is no problem because Coticules are not porous. It is important however that the stone is completely free of cracks. For that reason, Coticules are preferred that appear completely perfec!
t. For the way they are used and and because we are talking about knives instead of razors, rapid steel removal is desirable.
Coticule manufacturers used to keep a small – Kosher – stock of stones that met those requirements for their Jewish customers. The designation “Kosher” recently started to lead its own life among straight razor users. Although there is no single reason why Kosher Coticules would put a better edge on a razor than “select” of “standard” grade Coticules, there is a higher demand for them than they are currently available. As a result prices for Kosher Coticules have escalated.

It’s a wrong question, but since so many keep posing it, let’s try to answer it anyway.
Coticules fundamentally differ from synthetic hones in the way they abrade steel. Depending on how they are used, the rate of stock removal is variable, the level of polish is adjustable, and how fine the edge can be defined is changeable as well. How on Earth can that be reflected in a short and simple “grit” designation? For a true understanding, an in-depth explanation about the abrasive particles of Coticules, explains where that versatility originates.

Cutting SPEED:

• heavy, almost paste-like slurry: 1000 – 2000 grit.
• regular, milk-like slurry: 4000-6000 grit
• thin, misty slurry: 8000-12000 grit
• water: 16000 grit – or even slower.

KEENNESS level

• heavy, almost paste-like slurry: 600 grit, although less aggressive because the absence of a sawtooth pattern
• regular, milk-like slurry: 2000 grit, although less aggressive because of the absence of a sawtooth pattern
• thin, misty slurry: 6000-8000 grit
• water: 10000 – 15000 grit

SMOOTHNESS level

• slurry: surface looks sandblasted on a micro-scale
• very thin slurry: can be used to tone down harsh edges, very friendly for sensitive skin.
• water: will add smoothness to the feel of almost any other polish level without removing keenness up to 15000 grit.

Pre-dulling a razors edge on glass is performed by lightly dragging the edge of the blade once over a glass object such as the rim of a drinking glass, or neck of a beer bottle, using only the weight of the blade and no pressure. Afterwards the razor should no longer shave arm hair; if it still does a second, equally light stroke may be necessary.

An edge can’t develop keenness on a hone before both sides of the cutting bevel are completely flat all the way up to very edge.
It is of equal importance that the edge is free from the damage that accumulates at a microscopic level from the impact with coarse beard hairs.

By dulling the edge, and then setting the bevel until the razor shaves arm hairs, we can be completely confident that the sides of the bevel are flat, and the action of dulling on glass can also help with the removal of damage caused from the impact with coarse beard hairs.

Pre-dulling is also recommended when honing newly fabricated razors, because  the bevels on these razors aren’t always as one might expect.

Also, when a bevel has been set on a synthetic hone, it can be useful to re-dull the edge before starting to work on a coticule. The reason for this is that  synthetic hones, up to 2K grit, leave a saw-tooth pattern on the edge of the razor and leaving this edge as it is might not result in the typically smooth coticule edge.

Other than that, there is no special voodoo to the practice of pre-dulling a razor.
It renders a razor barely below shaving keenness. So barely that it can be stropped to shave again. But, if there is any convexity in the bevel, or if the razor was previously honed with tape, then the very edge will not regain a shred of keenness on a flat, solid hone before the bevel is entirely set. Things become easy after the edge has been pre-dulled. No second-guessing, no worrying. If the razor starts shaving arm hair again the bevel is ready for the next step of your honing procedure. It doesn’t matter what bevel setter you use, or what the next hone or step in the procedure will be.

Small nicks can be sanded flush with a good quality sandpaper of 300-600 grit. It is not advisable to use a pumice stone since it can leave grit in the leather.

If the cut resulted in a small loose flap, first glue the flap with cyano-acrilate (CA) glue (“wonder/super glue”). To do this, apply a very small amount at the bottom of the nick, press it firmly together, and wipe off any excessive glue. You will have to be very fast since CA glue sets very quickly, then sand smooth as above.

While not esthetically pleasing, small nicks do not compromise the performance of a strop.