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 Post subject: Nubatama Ume 2k - Olive brick of Joy :)
PostPosted: Fri Aug 03, 2012 11:58 pm 
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Nubatama Ume 2000 grit Waterstone: First Impressions part 1 of 2

I will be reviewing the 2000 grit Nubatama Ume waterstone, one of the latest additions to the Nubatama collection. It is olive or khaki colored, an 'Olive brick of Joy' :)

First impressions (dry) is a very silky smooth, reminiscent of some of the Naniwa stones.

Water absorption - not that porous, essentially a 'splash and go' stone even just misting rather than soaking the stone. I soak it for a moment while discussing some topics.

Why a 2k in general? I feel that between a 1k and 5k, the 2k gives a few advantages. Excellent for touchups where it is unnecessary to go down to to a coarser 1k stone. Also a good intermediary when abrading harder steels. Also for many purposes an excellent final edge when compared to a 1k edge. This stone because of its size should also work well as a superior stone substituting for the 1500 King stone commonly found in Sushi bars as a house stone. The 2k stone also reduces the wear on your more expensive finer grit stone.

Why did I bring in another 2k stone? We have the exceptional 2k Bamboo stone - but it is a more exotic and expensive stone and I wanted something more general purpose and affordable.

I test with a variety of knives in this video: a Sugimoto White steel short cleaver the size of a nakiri but more heavy duty - very handy knife. Next is a Misono Hankotsu - flat on one side and convex ground on the other. Finally a 330 mm Tojiro Gyuto, a stainless steel.

I demonstrate with the cleaver how to determine the existing angle with an edge leading stroke, feeling when the stone 'grabs' the edge 5:28. A very smooth stone.

I comment on not flattening stones in these videos initially - first because these are 'first impression' videos, second because I wish to demonstrate initial porosity and soaking times and third because the stone come out of the box quite flat already. I would certainly not object to anyone flattening these - or any brand or type of stone initially. Flat is always good.

I comment on controlling water volume on the surface of the stone to control and maximize grit density. Note me 'pushing' excess water off the top of the stone 5:44 to reduce water volume, allowing me to obtain a higher grit density sooner, since this stone absorbs water slowly.

The stone does generate a small amount of mud, to be used to advantage. It is a very pleasurable stone to use. The stone is medium hard to soft. When wet it becomes a darker olive or Khaki green color. Rather than waste mud, I wipe it off the blade and put it back on the stone. Brings the knife from slice cut only to ~ 1inch out push cutting. A moderate mirror finish.

Next the hankotsu - a heavy short knife used for a hanging style of butchery. I also use it as a steak knife and this does dull the edge more quickly, which is why the knife requires sharpening. Initially the knife will barely slice cut paper. The back is sharpened just barely less acute than lying it flat against the stone. Using the mud generated from the first knife lets you get a smoother feel. You can cut into the stone on edge leading strokes if you are too sloppy in your control of knife angles. Note that when you feel the knife digging in a bit on edge leading strokes that this more rapidly increases the mud density, adding stone particles to the slurry. I do catch the stone a bit 15:29 in a sloppy stroke, something I have done on the Naniwa green brick stone too. A bit more time on the stone shows improved cutting performance, with excellent slice cutting and close in push cutting.

I also demonstrate stropping on a piece of paper. This should be done with better support of the paper. The finish produced is an appropriate final finish for the intended use of this knife.

Next the 330mm Tojiro DP knife, an HRC ~ 61 stainless VG10 type steel in need of a touchup. I discuss sweeps, fully utilizing the full length of the knife reducing flattening requirements. I also discuss edge trailing only pushing water towards one end of the stone. These long knives I find useful for initial prep of food, breaking down multiple pieces of produce - watermelon, bunches of food etc.

I also demonstrate sweeps keeping the guiding fingers over the stone as the blade sweeps beneath the fingers, sectional sharpening and 'w' strokes, linking a series of partial sweeps together.

I use these highly water absorbent towels - used typically for car washing - available at Costco or automotive stores. A well dried knife gives you MUCH more accurate sharpness testing, since any moisture will decrease performance of sharpness testing - wet paper is useless for testing and a knife retaining moisture won't cut as well. Worth the small extra effort.

The finish on the edge is a slightly matted mirror finish. Edge testing is incomplete and continued on another short video.

http://www.youtube.com/watch?v=S4Yz0eco ... e=youtu.be

This short video is cutting testing after further refinement of the edge from the previous video. The cutting tests at the end of the previous video did not reflect the true performance potential of the stone and were, in retrospect premature testing of the incompletely refined edge. Note in particular the increased push cutting performance.





This short video is cutting testing after further refinement of the edge from the previous video. The cutting tests at the end of the previous video did not reflect the true performance potential of the stone and were, in retrospect premature testing of the incompletely refined edge. Note in particular the increased push cutting performance.

Available at Chefknivestogo:
http://www.chefknivestogo.com/nubatamaume2k.html

---
Ken



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