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recently obtained another Coti at a flea market. This is the third one that I've had no luck with. I lapped it up to 1000 grit wet-dry. Had a rough feel but I tried it anyway with lather and then running water to refresh a razor. It shaved but was rough. The scratch pattern looks coarser than my 1k Naniwa. I was sure it was used as a razor hone as it was in a box including a Swatty. Is this normal for a Coti or is there something else i need to do to to prep the surface?
Coticules are all over the place.
I have one that is terrible - maybe 1k but even thats a stretch. I can't in good conscious sell it.
I have a few that are incredible, as good an edge as an Escher. These are rare for sure!
One found at an antique store and two labled Pike Coticules, one "Superfine" and one "Extra Choice Select"
I also have a 4x2 that is just as good but doesnt get used as much due to size.
They are the most variable stones given they all came from the same place.
Some claim that if you contact Ardennes and ask specifically for a razor hone they will find one for you. I'm sure it would set you back some.
If you are planning on picking them up anywhere it is a crapshoot. Good luck!!
I don't think that the wet dry is going to smooth the garnets no matter what grit you go to.
Volcanos and sediment at the bottom of the ocean are hard to predict.
Bacically with these you have to learn the hone.
Not make the hone do what you want.
Contrary to popular belief, not all coticules are razor quality.
I have heard many say you have to learn the coticule and any coticule can be made to make a razor shave well.
I have to call bullsh%$t on that one!!
Really really good razor quality coticules are not common. Many will be "ok", a far cry from excellent. Some are down right crap.
Lapping with w/d will work but it wont make the stone something it isnt.
Many still use a finisher after their coticule so that might tell you something.
I would say, like some, that an average coticule might be 8k equivilent or less.
The really exceptional ones are rare but they are out there.
Ardennes has stones marked standard, select and select plus. They claim the only difference between standard and select is appearance and all have grit ratings between 6k and 8k. The select plus are from veins known for superior razor honing capability.
They also have unmarked coticules and BBSs they recommend for use on tools. Cotis were also used to keep carpentry tools true and sharp.
I have been lucky in that all the coticules I have produce a decent edge on my razors, but some are clearly superior to others. I go on the assumption that the edge I get from a coti is from a hone in the 6K range and use a finisher or chromium oxide pasted strop after that.
They are natural stones and can vary significantly. In my experience, lapping a coticule is useful for ensuring you have a flat starting surface, but it won’t impact the abrasiveness. The garnets in the coti are the shape, size and are distributed how they are and lapping will have no effect on that. Some are hard, don’t self slurry and can be excellent finishers while others are soft and slurry easily and can be used to reset a bevel.
Articles I’ve read indicate there is greater variation in abrasiveness and hardness amongst coticules than can be found in BBWs even though they come from the same quarry.
Okay. still seems odd that people for ages past used them to maintain their razors. Was that the best they could get? (I did get a smoother feel on the stone after I rubbed a small fine diamond hone on it. Afraid to try it on a razor again though)
You may have had stray grit on the stone. Do not use slurry on it. Dress it to 1k, clean well.Quote:
Originally Posted by tintin
Do not use anything but water to test it. You do not have to use running water!
Use a razor that already has a decent edge. If you have magnification you can see if it improves the edge visually.
A coticule may feel very nice on the face even though the edge doesn't look too good under magnification. It will not be the closest shave but will be face friendly, so shave anyway.
An excellent coticule will leave an edge both looking great under mag. and shave great.
When you raise a slurry on the coticule, which you did with the diamond hone, you lower the initial “grit rating”. As you hone with water, the activity causes the loose garnets to break down and the grit gets finer until you finish with just water and reach the limit of the stone’s grit fineness. It’s that final abrasiveness limit that determines how well the coti will finish an edge and whether you need to move to another finisher or paste.Quote:
Originally Posted by tintin
Some cotis are just better for razors than others and the Ardennes stamps indicate how they rate each stone. I’ve found their ratings to be pretty accurate.
I don't believe garnets break down in use.Quote:
Originally Posted by DZEC
You are using slurry to quicken your work and flushing them away till you are on the stone itself.
I stand corrected. Thanks.Quote:
Originally Posted by stoneandstrop
This is one of the best summaries of coticule honing I’ve seen.
https://www.badgerandblade.com/forum...254715/page-24