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  1. #1
    Join Date
    Apr 2007
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    Adelaide Hills, South Australia
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    Default Hishiboshi karasu #9k synthetic-natural waterstone

    I recently gave the new Hishiboshi karasu #9,000 synthetic-natural waterstone a test run.

    A synthetic-natural waterstone? How come? Well, it's compounded from "natural stone powder" but fired in a kiln the way that synthetic waterstones are made. This method is not altogether new. I understand that there are other man-made/synthetic stones that have been made with some natural stone content, but in the case of this stone the selection of "high quality" content to optimise the natural stone feel and finish was the primary purpose in its creation.

    To help create a natural stone appearance, the stone has some darker coloured specks through it, thus the name 'karasu' (translation = black crow point) which are the dark areas of mica that add additional abrasive power to some natural stones. I was unable to determine if the dark spots in this stone serve the same function or are just there for appearance/marketing purposes. The speckles do give the stone a nice bird's egg appearance which is not unpleasant even if they turn out to be irrelevant to the stone's performance, and certainly not a disadvantage when identifying the stone amongst others.


    Like natural stones, the Hishiboshi karasu doesn't need much water to get it going; just a light sprinkling or spray of water and a gentle nudge with the diamond plate and it was under way giving an immediate showing of coloured mud from abraded metal particles. This is typical of an aggressive stone, which this one is for a high grit finishing stone. The karasu particles may add to the impression of a quick dark mud, but the higane (hard steel) of the blades did quickly come up to a polish, which is the real test.

    As for feel and finish, this stone is the nearest to a natural stone that I have experienced in a synthethic. It is a very smooth stone, one of the smoothest that I have used, and while slightly on the muddy side (which I like) it was reasonably resistant to dishing. Overall, a real pleasure to use.

    What can I compare this stone to?

    I tested it alongside a Sigma Power #8k stone and some naturals. The Sigma felt distinctly chalky in comparison and without the benefit of my image capture microscope (which had a mishap, but soon to be replaced) I would say just doing a naked eye visual comparison that the Hishiboshi takes the abrasion pattern above the stated #9k, with some variation, as might be expected from its natural stone content. Not surprising is the variation I got in the appearance of the 'jigane' (soft metal cladding) off the Hishiboshi, which ranged from just below a full bright polish to a bit of cloudiness, but I'm not sure that I have worked out yet how to fully control that. But I can say that I have never been able to get that range off any other so-called synthetic. The blades that I was working with had both soft iron and stainless cladding.

    When my image capture microscope arrives I will add some close-ups of the abbrasive pattern off the stone.

    My natural finishing stones all went well above the finish off the Hishiboshi #9k, but so also do their prices. However, the Hishiboshi is the closest to a natural stone that I have experienced at synthetic stone prices. I paid A$85 for it from So-san (here at Japan Tool).

    Here is the competition (from Stu at Tools from Japan) the King Gold #8k for about the same price, the Naniwa Ebi #8k and #10k about the same, the Suehiro G8 (green carborundum) or W8 (alundum) or Cerax #8k for about the same, Suehiro Gokumyo #10k over twice the price, the Sigma Select II #8k for about the same, the Sigma Power #8k for a bit less and the #10k and #13k for a bit more, the Shapton Pro #8k and $12k for about the same, and from Carbatec here in Oz their no-name #8k for $140.

    All of those stones have different characteristics from one another and most are very different from the new Hishiboshi stone. Some of them may suit your purposes and preferences better, but from my understanding of what each offers, if I were to have just one synthetic stone in the #9k range it would be the Hishiboshi Karasu.

    Neil

  2. #2
    Join Date
    Feb 2014
    Location
    Brisbane
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    44

    Default

    I'm so glad you got to test it and your findings have certainly justified my own thoughts on the stone. I enjoyed it from the get-go but it's good to get the opinion of someone with far more experience than my own. For the price, I think it would be hard to beat. Have since used it on a number of steel types and it seems to a good job on all, but my Tadafusa Santoku (Blue 2) loves it.

  3. #3
    Join Date
    Jun 2007
    Location
    Austin, TX
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    Very interesting, this whole topic of a combination of natural stone with synthetic binding. I was guilty of thinking that this was how all synthetic stones were made, from crushed stone rubble plus some glue of some sort. But apparently not so; so how are synthetics made?

    Thanks,
    Pam

  4. #4
    Join Date
    Apr 2011
    Location
    McBride BC Canada
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    Default

    That's very nice.
    What are the proportions of grit to binder?
    What is the nominal grit partical size +/- SD?
    What is the density/hardness of the binder?
    I have some charts on paper(somewhere) for these things.

    But to tell me that you have a Wackafumi organic stone
    needs some expansion.

    These guys do not want to tell you a whole lot about the art-stones that they build.
    They need to sustain the mystery, the cache` of the stones that they sell.
    Bunch of horse puckey, I say.
    Gimme the numbers. I can make up my own mind.

  5. #5
    Join Date
    Apr 2011
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    McBride BC Canada
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    Default

    Thanks for the link to the catalog.
    Time for reading.

  6. #6
    Join Date
    Apr 2007
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    Adelaide Hills, South Australia
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    Hi RV

    Quote Originally Posted by Robson Valley View Post
    What are the proportions of grit to binder?
    What is the nominal grit partical size +/- SD?
    What is the density/hardness of the binder?
    You get more of that type of specification when you buy a high speed grinding wheel, but in my experience the average craft user is unable to interpret such specifications anyway. They just buy a wheel on reputation, the advice of others, or the recommendation of their craft supply shop. If you asked them why they went with a K wheel they just look blankly at you or say, because that is what experienced craftsperson X uses.

    It should be different in industry, but again in my experience in trade training they get taught about these things then go and select whatever their mates are using in the industry. Occasionally you come across a production engineer who understands what is needed for specific applications.

    Quote Originally Posted by Robson Valley View Post
    But to tell me that you have a Wackafumi organic stone needs some expansion.

    These guys do not want to tell you a whole lot about the art-stones that they build.
    They need to sustain the mystery, the cache` of the stones that they sell.
    Bunch of horse puckey, I say.
    Gimme the numbers. I can make up my own mind.
    What can I say, I haven't heard of horse puckey as an ingredient in any of the stones, but you never know... : ~}

    I do have a little experience with high fired ceramics and know that the manufacture of synthetic waterstones is a highly technical and controlled process. I have no doubt that the engineers involved have all manner of specifications for their products. Given my background I could perhaps understand some of those specifications if they were provided, but find something like the following analysis that Stu has undertaken far more useful.

    Waterstone testing, the results. Part I.

    As for the mystery, anyone who still hand sharpens a blade is walking on the dark side and we darksiders can cope with a little mystery...

    Neil

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