Forcing a patina on the Shigefusa 240 kasumi Gyuto

This little experiment is a result of the Great Gyuto Shoot-out, where the Shigefusa 240 kasumi gyuto proved to be very reactive to a lot of different foods, and pushing it down to a runner up position beat by the excellent Devin Thomas stainless gyuto.

Using the Shigefusa over time will slowly but sporadicly build a patina on the blade. The result, however, is a long period with a partly reactive, seriously spotted and not very elegant knife. The solution is obvious. To force a patina under controlled circumstances, evenly building a patina on the entire blade layer after layer. Again, Mr. Øyvind Dahle put his precious knives at stake for me to play around with. Thanks, man!

Setup: Knives, mustard, vinegar, lemon, cotton cloth and finger stones

For this test I had access to a second Shigefusa. A nice Kuro uchi nakiri, probably with the same core and cladding as the gyuto. As the exposed area of reactive metal is a lot smaller on the Nakiri than the Gyuto, this would be the perfect place to test out the acidy mix before going all in. Before starting I used some fine stone slurry on a cotton swab to polish of any old spots and removing all traces of fat and dirt from the blade. 

Building a Nakayama Aka-pin slurry

Priming the polishing cloth with slurry



Removing stains and fat from blade



I used a 50/50 mix of Dijon mustard and white 7 % cooking vinegar and added a small squeeze of fresh lemon juice. This gave me a very nice "paint" easily put on with a silicon brush. Any brush can be used, but a silicone brush will be reusable after a good wash. 

After cleaning up the blades, I took them to my water tap and using the warmes water available I heated the blades. This heating will make the acidy liquid evaporate quicker, and by doing that making the surface of the steel react more quickly with the oxygen making a patina form on the steel more evenly.

Heating the blade under running water to acellerate evaporation and oxidation (patina) on the blade



Thick layer: Slower method, but it works fine

Thick layer: Slower method, but it works fine

Shigefusas curing, slowly building a patina. For the patient souls.

I tried two different ways to apply the solution. One was to brush it on with the silicone brush as shown above. The other was to apply some of the solution on a cotton cheese cloth and wrap it up so that only the thin liquid was filtered through the cloth and applied to the blade as shown below. This last method proved a lot more efficient as the liquid was applied thinner, cooling the warm blade slower thus making it evaporate a lot quicker on the preheated blade and building a thicker patina.  

Adding a thin layer on warm blade proved to be quicker and easier done



Priming a cotton cheese cloth



After experimenting a little back and forth between the two methods, about 20 heatings and acid applications in total, I cleaned the blades off for an inspection. At first it didn't look like it had built a patina at all. However when placing a new stainless blade on top, I could easily observe the very nice almost champagne coloured patina that had formed on the Shigefusa blade. The hagane had blued up as expected, but as I had expected this blueish colour on the entire blade I was a bit surprised.  

Note difference in color between patina on the Shigefusa and the stainless steel

It was time to put things to the test. To see if the patina was resilient enough for normal use or if it would wear of at the first contact with real food. It was time to get Shiggy with it :o)

First up were a couple of ripe tomatoes. Usually this would stain the knife significantly, but the nice patina stayed nice with no new stains or ugly smell developing. Then a spiced raw chicken breast. Still nothing. Then I sliced the cooked chicken while quite hot. Still no reaction. The patina looked stable. After cleaning the knife off after slicing the hot chicken, the parts of the blade that had touched the warm protein had blued up a bit like the hagane had done in the first place. However the patina held up nicely and the blade did not react negatively to the protein. Very good!

 

After this rather uplifting experience I decided to put the patina to the ultimate test. The most reactive food from the shoot-out, the dreadful cabbage! I used the Shigefusa to finely slice the cabbage into angel hair slices closely observing the blade, but nothing happened. Nothing! I got braver. I buried the blade in the freshly cut cabbage strands, really packing it around the blade and let it sit there for 10 minutes.



Shigefusa in cabbage hell



Coming out of it with bells and whistles. I believe we have a winner!



Before this process the result would have been a partly black, partly rusty mess of a gyuto, but after pulling the blade out of the cabbage heap from Shigefusa's personal hell, it showed no sign of reaction. The cabbage was fresh, the blade still looked good and no nasty smell was evident.

Most important of all. In my opinion, the Shigefusa gyuto is still the best performing gyuto around by a good margin. With the nice patina forced on the blade, bringing the heavy reactivity to food under control, you no longer have a good reason not to want one. This is an absolute marvel of a knife, and I want one my self. Badly! Case closed!

The great Gyuto Shoot out!

After two full days of slaughtering produce, here are the final result of the grand gyuto shoot out. My good friend and fellow knife nut, Øyvind Dahle, kindly put up his collection of custom gyutos to the test. I brought only my trusty Takagi, but as you all know by now, I am more of a yanagi guy.

As mentioned the test was conducted over two days. We had one day of testing out the knives, collecting first impressions and testing and selecting stones for the final sharpening, and one day really sharpening up the contestants and comparing them in a more detailed cutting test setup. We also did some test sharpening on a lot of different stones to pick a sharpening setup for day two that would give the knives as similar and as sharp edges as possible for the different steels. Here are som pictures from day one, cutting cabbage and prequalifying stones for day two and serious sharpening. 

 

Trying out the Oohira shiro suita

 

Oohira asagi ready to go



 



Devin Thomas 240 vs cabbage

 

Hiromoto 240 vs cabbage

 

Shigefusa 270 vs cabbage



After a wonderful cutting frency with some of the absolutely most beautiful and high end gyutos available, it was time for some serious testing. and comparison. Even on day two I was just cutting produce, as produce comes in a wide variety of size, structure and toughness. I went to my grocery man and picked out some large carrots, large hard potatoes, ripe tomatoes, some red chillies, a couple of large onions and a big chunk of fresh ginger. Ginger has a very fibrous core and will really put the edges to the test. I saved that for the finals. I also had some cabbage left from yesterdays cutting frenzy with Øyvind. Here you can see the choice of produce I used for this test. Also a closeup of the brave contestants.



 

From the right you have the Shigefusa 255mm (actually it's more like 270, so I called it 270!)  with a beautiful custom handle by Marko Designs. Number two from the right is the Hiromoto 240mm with a very nice custom handle by Dave Martell. In the middle we have the grand Devin Thomas 270mm forum prototype with a custom handle by unknown maker (Devin?). Then the beautiful Devin Thomas 240mm again with a stunning custom handle from Marko Designs. And finally to the very left, my trusty Takagi 210 with a custom handle by me. Except for my own Takagi that I have built a very solid patina on, they were all nice and shiny. Getting to know them only yesterday, I couldn't wait to put them all to the test.

As I mentioned, the first thing I did was to sharpen all knives using the stones we had matched with the steels the day before. All knives were fairly sharp, but all had some potential, and in addition I wanted them all to have similar edge geometry to be able to compare them with one less unknown factor.

The stones that were chosen were my very good, efficient and even grit Oohira asagi as pre-finisher for all knives. Then three different finishers for different steels. A Nakayama karasu for AS and SS, a Nakayama nashiji kiita for the Shigefusa Sweeden steel alloy and finally the Oohira shiro suita for my Takagi Aoko #1 honyaki. Just for the fun of it I tested all knives with all finishers. If a finishing stone was a total mismatch with a knife, I went back to prefinish on the Oohira asagi before I took the knife back to the finisher particularly chosen for the knife, to regain the best possible edge for each knife. 

From top: Nakayama nashiji kiita, Oohira shiro suita, Nakayama karasu, Oohira asagi

I made a judgement on sharpening feel and the edge on each knife off each stone and gave each knife/stone combo a "Match point" describing how good the match was and put it all in to a table. A score of 1 equals no match between stone and steel while 5 equals a close to perfect match. The results may be interesting when choosing your stones for a given steel, but I make no guarantees as results will vary. You will still have to experiment, but maybe you can narrow down your selection a bit.

After finishing all knives as sharp and as close to each other as possible, I went on doing the veggie cutting tests. Here are some pictures from the testing.

 



Shigefusa potato slice :o)



Shigefusa reacting to cabbage



For each knife and each type of vegetable I judged the percieved sharpness of the blade. That is the force I had to use to drive the knife through the vegetable. A score of 1 equals a lot of force needed while a score of 5 equals very little force needed (of course relative to the vegetable in question). The force needed wil depend on several things lik the geometry of the blade, the taper from the spine to the edge, the structure in the grind on the blade and so on. I also made a judgement of how well I could feel the structure of what I was cutting. If I could feel the layers of the onion or cabbage or the fibres in the ginger root. Finaly I looked at how the steel reacted to different foods and if the steel was discoloured and produced a smell that transferred to the food. A score of 1 equals not reactive and a score of 5 equals extremely reactive.

To sum this up I had several favourites during the test and a few disappointments. None of the knives were consistently best at everything, and most knives were fairly good at most tasks. However, the Shigefusa stood out clearly in the cutting department. There was something about how the Shigefusa just slid through the food totally effortless that was very close to magic. It felt like cutting soft butter with a warm knife. So as far as pure feeling of cutting goes I would have to declare the Shigefusa as the winner with the Devin Thomas 240 as a close runner up. 

The knives resting out with the final results

One HUGE drawback I experienced with the Shigefusa was that it is exceptionally reactive to several kinds of vegetables, particularly the cabbage and onions in my selection. This reactivity resulted in discoloured food and steel and an ugly sulfur like smell from the blade. I really don't understand Tokifusa Iisuka's choice of cladding steel for this knife, as the core steel is like something out of this world. 

Taking the heavy reactivity to food in to account, the gold medal will have to be passed over to the Devin Thomas 240. An exceptional knife in every way. Well balanced and beautifully made and a wonderful all round performer. I particularly liked that it gave a very distinct feel of the structure of the food I was cutting. I could almost feel the freshness of the tomatoes through the knife. The Devin Thomas knives are relatively easy to sharpen but quite sensitive to the choice of finishing stone. Both DT knives were a disaster on my Oohiro shiro suita, but matched very well with the softer Nakayamas and took a very keen edge. 

The Hiromoto was a good overall performer that did absolutely nothing wrong and that will satisfy a lot of  users. It is very comfortable to use and very well balanced. It was easy to sharpen and to get sharp. To my satisfaction, my trusty old Takagi held its ground against these race horses as far as sharpness and cutting goes, but I sadly came to the conclusion that it is actually way to light for my preferences, and I will probably in the market for a somewhat heavier knife pretty soon. I really liked both Devin Thomas knives, and the Hiromoto was also a very enjoyable aquaintance. The Shigefusa, no matter how magic and beautiful, had this issue that was very hard to ignore.

I had a lot of fun doing this test. Thanks again to Øyvind who trusted me with his precious knives.

Next blog post will be "How to force a patina on Shigefusa kasumi gyuto" ;o)

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