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Cotcarb - an earnest review


Well-Known Member
About a year ago, I brought 2 so-called "Cotcarbs" with me from one of the visits to Ardennes. I had seen them over there before, knew what they were, but never really got around trying one. Around that same time, a few of our members were looking for a cost-effective hone to repair damaged razors' edges and jump straight to a Coticule after that. Sliced bread for a DMT-600grit, but there are plenty of equally great alternatives on the market of synthetic hones. But what about the "Carb" side of a "Cotcarb"?

For those who've never heard of it, a Cotcarb is a thin BBW glued to a thin carborundum stone of approximately 600 grit. It is produced by Ardennes Coticule and aimed to a pocket/kitchen knives market. It is sold in several dimensions, from small pocket models to large bench stones.

Here's a picture (from Ardennes' website):

There's also a variant, glued to a wooden paddle:

It sounds like an excellent idea, and I wondered about the quality of the Carborundum side for razor repairs.
I tried it a couple of times and came to the conclusion that the carborundum is really not of the best quality. It's rather gritty, and doesn't survive a comparison against my DMT at 600 grit, which has not only a smoother action but is also faster, doesn't need lapping, doesn't glaze and blablabla. But for sharpening pocket knives the Carborundum side functions, and I wouldn't mind carrying a small one in my backpack during a long hiking trip. It would not only serve to repair the occasional chip in the edge of an abused camp knife, but as we now know, the BBW also puts an edge on a straight razor that leaves nothing to be desired. Sharpening and shaving in the wild, do it once and become addicted!

Nevertheless, as sound as the idea may be, it appeared to me that this product can be improved. Personally, I found the carborundum side a bit too coarse to hand over the edge to its BBW counterpart. For softer pocket knives there's no real problem, but for harder steel, the BBW struggles seriously while dealing with the edge roughness left by the Carborundum. Were it one of the faster Coticule layers instead of the BBW, the story would be different. But even then, the Cotcarb concept would *really* benefit from a better grade carborundum or other synthetic stone in the 600-1000 grit range.

I have sent a Cotcarbs to one of our members, MarkinLondon, and here's his verdict, shared in an e-mail a couple of days ago. (Note that Mark may not have been aware that Cotcarbs exist in larger dimensions as well):
MarkinLondon said:
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In conclusion, a good idea, certainly when it comes to portability in situations where a very fine edge may be required (the BBW), but the "carb" they've glued it on doesn't really do it justice. It cannot be called an strong marriage and will therefor probably never fetch the reputation of, let's say a Norton 1K/8K combination hone that sits on many tool benches. A bit of a missed opportunity.

Best regards,


Well-Known Member
Thank you for the review, Bart. I'd been curious about them. Unfortunately, no one in the US seems to sell them, and, considering how readily available carborundum hones are here, it didn't make sense for me to order one from Belgium.

I've heard some good things about some Japanese-made low-grit carborundum waterstones. I wonder if it would be economically feasible for Ardennes to look into those as an option.


Well-Known Member
hhmmm. Very interesting, indeed.
Thanks, from me as well, Bart.
I have to admit, i'm not a fan of synthetic stones, in any shape or form, that being all I used for the vast majority of my life.
It's unfortunate that the Ardennes has paired two such disparate stones together. Have you mentioned anything to them about it? I can't help but think that the problem with it isn't that it's a crappy stone, rather that the BBw hasn't got the speed to overcome the roughness left by the Carbo side. I wonder if the coticule wouldn't be a better pair than the BBW?;)


Well-Known Member
Tri-hones as shown below with one synthetic, and two Arkansas stones seem to sell well in the US.
One thing going for it is that it traverses a bigger grit range.
For Ardennes, a tri-hone with one interrupted-surface 600 grit DMT + BBW + Coticule will be perfect.
Thanks for the review.


Well-Known Member
wdwrx said:
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Technically, I think you're right, but I think it will always be problematic to combine a subpar product with a high quality one. The sum of that exercise will always reflect badly on the higher quality product. I think it is the weakest link that demands to be upgraded.
I also think it is a matter of opening new markets. They don't really need to open new markets for Coticules, as the demand exceeds the rate at which they can mine and produce Coticules. But for the BBW, I think it is different, hence the creation of a product line that could meet new demands.
The core of the problem is that they have, in my opinion wrongfully rated the BBW as "4000grit". I am personally opposed against grit-rating natural hones, as this usually makes little sense, but I understand that it is necessary for the sake of selling hones in today's "grit" oriented market. Yet rating the BBW "4000" is in my opinion a mistake. It is considerably finer and also slower than the average 4K synthetic hone. If you put a shotgun to my head and make me rate it, I would say "10K". It is comform with the kind of sharpness and smooth cutting action that can be obtained from this stone, and it offers a more realistic prediction of the speed that can be expected.
If looked at it that way, the synthetic side of a combination BBW would better be a good 3K hone. It would be a stellar combination for razors and also for other cutlery it would perform very well. When free handing kitchen knives and woodworking tools, most people don't want to do many laps, for the simple reason that it demands so much attention to maintain a correct sharpening angle. On a razor, it doesn't matter, because it maintains its sharpening angle automatically, but for other cutlery you want to make a limited amount of high precision laps and arrive at the desired results.
With what we learned from the BBW-study and how these result are comfirmed by a growing number of users, it is almost a crying shame that so many have treated it as a "4K" in the past, and followed it by hones that obscured the true capacities of the BBW. In that sense, the Cotcarb is the culmination of a failed marketing strategy. All in my humble and at times controversial opinion of course.

Kind regards,


Bart said:
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That has always puzzled me too. Have you any idea how they arrived at the 4000k figure? I'm at a loss to explain it to myself. Also, thanks for the review, I've been curious about the cotcarbs for a while.


Well-Known Member
I think it was mainly marketing. In a world that's dictated by synthetic hones, many insist on numbers for natural hones as well. At the time they started rating Coticule, I suspect that 8000 was about the highest on the synthetic market. And because the results are in no way less than that of a synthetic 8K stone, they rated Coticules at 8K as well, even though there is no direct correlation with the average garnet size of Coticules. The garnets, due to their shape, cut wide and shallow, whereas particles of man-made hones typically cut deeper in relation to their diameter. Coticules have roundish garnets with a hardness of about 7.5 Mohs. Synthetic hones tend to have spiky particles with hardnesses well above 8 Mohs. In its upper region, the Mohs scale is more or less logarithmic, so these are serious differences.

When they introduced the BBW onto the market, it was determined that the average garnet size of BBWs is larger, and the logic of synthetic hones dictated that the grit rating was adapted accordingly. I think "4000" was considered a good marketing point.

But it never made sense to me either. The stone was supposed to be coarser, but it was slower at the same time. And it never appeared to be coarser in the results it delivered.

Kind regards,


Thanks. Nice to have my puzzlement confirmed by one who knows better than me. 4k? A mystery. Thanks again.


Well-Known Member
The idea is great & I thank you for the review Bart!

I have been suspecting that the Carb would be inferior, because of the price.
And now I know for sure.

There is actually rather big differences in various carb-stones.
The cheap ones can be ha for next to nothing, but they perform cheaply too,
pretty much like the one in your test.

However, if you drop around 15-20 bucks you can get a good carborundum that actually works well
as a bevel correcter, both on knifes & razors.
If one of those were to be coupled with a BBW, you'd have your ideal "Kitchen hone"
Infact I do most of the kitchen knifes I sharpen on my carborundum & then on to the BBW.
So it's a great idea for a product, they just have to get themself a better carb-stone.

Here's a (in my opinion) good carborundum. About 1/5 of the cost of a DMT
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Let's not get carried away with creating some sort of mystically perfect combo hone when many of us already have the tools we need to maintain kitchen knives. What my tireless reading has revealed is that a bevel can be set by anything from 600 - 1200 and that hones capable of sharpening razors can be used to finish a chefs knife.

So: grab your Namiwa 1k and your favourite BBW and attack your kitchen knives with verve. Tomatoes will cower in fear at the sound of a knife being pulled from the block and are very likely to slice themselves wafer thin rather than wait for the steel. I know things. I know how things are.