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Sharpness question from a newbie - tomato problems
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Thread: Sharpness question from a newbie - tomato problems

  1. #1
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    Sharpness question from a newbie - tomato problems

    Hi all, I'm new to the board and relatively new to Japanese knifes and sharpening with whetstones.

    I'm a home cook based in the UK. I recently purchased a Hiromoto AS gyuto (240mm) from JCK as well as a JCK 400/1200 grit combo whetstone and a JCK 6000 grit finishing stone. I previously used a stainless Sabatier and have practiced my sharpening a few times (using online video tutorials) on that before trying out my Hiro on the stones. I think I've got the basics but there's so much to learn!

    I'm a lefty and asked JCK to adjust the asymmetrical bevel on the Hiro from 60:40 to 40:60 (not something I fancied doing myself having never sharpened a knife before!). The OOTB edge seemed quite good to me but my frame of reference is somewhat limited by inexperience. After a week or so of use, I touched up the edge on my 6000 grit stone. I only recently sharpened the edge properly (i.e. 1200 grit followed by 6000 grit, followed by deburring with a cork).

    Since then, I have used it to chop veg and it goes through onions very well; much better than ever before. It seemed really sharp but I haven't done any of the normal tests that people recommend (I did rest the knife edge on my thumb nail and it digs in a little and leaves a small scratch. Not sure if this is a formal test, or what it shows exactly!). Yesterday - and here is the crux of my question - I used it on some slightly overripe cherry tomatoes and it didn't go through them as easily as I'd expect (or as it did with the OOTB edge). It took a good couple of centimeters of pushing to break the tomato skin. And it even squashed some of the more overripe tomatoes. I then tried it on some quite overripe normal tomatoes (that went past their best before date over a week ago) and, again, it didn't break the skin immediately but required a couple of centimeters of movement to break the skin.

    My question is: has anybody encountered similar problems with a seemingly sharp edge and overripe tomatoes? And if so, how can I remedy this? Given how the knife performs with everything other than overripe tomatoes (the edge is certainly sharpener than it was OOTB), I am minded to think that one of the factors contributing to the issue is the overripeness of the tomatoes but want to know how I can fix it.

    Any tips would be greatly appreciated

  2. #2
    This video might be helpful
    http://m.youtube.com/watch?v=lqsbO1w8rXE
    Huw
    In order to make delicious food, you must eat delicious food. Jiro Ono

  3. #3
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    Great. Thanks for this. So it looks like I probably polished my edge a little too much.

    I guess the best way to fix it is to take it back to the 1200 grit stone again and spend less time on the polishing stone.

  4. #4
    Quote Originally Posted by Von blewitt View Post
    This video might be helpful
    http://m.youtube.com/watch?v=lqsbO1w8rXE
    I'm not entirely sure this video is accurate. He makes good points, granted, but an edge DOES cut even when there is a mirror finish. The reason the knife slides in the video isn't because the knife has too high a polish. It is likely because it was not sharpened properly, specifically the apex was rounded.

    Just make sure you're paying attention to geometry and do a little more research.

  5. #5
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    I love a polished edge for most vegetables, so I keep one knife at a mirror polish and another one toothier for soft tomato skins and the like. If you do this, you will have to keep your polished knife pretty sharp, because as many here will tell you, a dull polished knife is inferior to a dull toothy knife (but, IMHO I'd take a sharp polished knife over a sharp toothy one for 90% of tasks).

  6. #6
    New sharpeners wobble and thus round over edges easily. Also, some stones in the medium grit level will over polish the edge. When combined these two factors make for a sharp but slick edge, an edge that will slice but not push cut.

    To combat this effect take it S_L_O_W and be deliberate, try to not cut in multi-bevels as these can turn into a rounded over bevel easily on the next stone up in the progression.

    Also, it's best to not go much higher than a medium-coarse stone like a 2-3k (max) at first. As you get better introduce a medium-polishing stone (4-6k) that is known for leaving a bite to the edge. No need to go higher than this for a gyuto.

  7. #7
    Senior Member Mrmnms's Avatar
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    A while back, Will Catchside, an awesome maker here suggest I tried stopping lightly on a 2k stone after I finished polished up my bevel, to give some tooth to certain knives. You may try a few edge trailing strokes, lightly, at a lower grit , for soft foods.

  8. #8
    Once you get more accustomed to sharpening, stropping with a diamond spray can really help in this situation. That's fairly advanced though.

  9. #9
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    Thanks for all the tips, guys. Dave - I think you may have hit the nail on the head with me wobbling! Any tips on how to maintain a constant angle (other than taking it slowly)?

  10. #10
    Quote Originally Posted by Mangelwurzel View Post
    Thanks for all the tips, guys. Dave - I think you may have hit the nail on the head with me wobbling! Any tips on how to maintain a constant angle (other than taking it slowly)?
    http://youtu.be/GB3jkRi1dKs
    http://youtu.be/SKeSRDMRpY0

    JKI Sharpening Playlist
    https://www.youtube.com/playlist?lis...ature=view_all

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