Shigefusa 270mm kasumi yanagiba with custom, by me, desert ironwood handle

14 Jan 2011

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. √ėyvind 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!



12 comments:

  1. Nicely done! I like to apply a solution of baking soda and water between acid applications, just to fully neutralize the acid.

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  2. He He I did not know that you made silicon implants to his Shigi :)))

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  3. When you did the 20 applications, did you wipe the solution off with hot water and then re-apply it? or did you just paste over what you already had? I just got a full carbon knife, and it is very reactive.

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  4. The solution can be spooned on the cheesecloth and closed in. I used triple folded cloth so that I got 6 layers of cheesecloth as a filter. The outside should be well saturated.

    Apply on the heated blade, let dry, apply another layer, let dry, wait for a couple of minutes, rinse off in hot tap water and repeat this process 4-5 times or as many times as you like.

    This will give you a champagne patina (at least on the Shigefusa steel).

    If you then bake a chicken breast in the oven until totally cooked through and slice the mustard patinated knife through the breast to divide it in two flat slices so all of the blade is evenly heated from the chicken meat and covered with the hot protein, you will get a blueish patina. Use the sliced chicken like the cheesecloth and cover the blade with warm protein juices.

    Hope this answers your question.

    Best regards and good luck

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  5. Ah that helps a lot, thank you.

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  6. Very interesting post.

    I have a shigefusa coming soon and I might try this.

    Quick question, though.

    If I am trying to shift the patina from the champagne color to more of a blue, is it the protein or the heat from the chicken that produces the shift? Or both?

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  7. You can start out with warm protein on a fresh blade if you want. It is more difficult to get an even result, but the reaction will be very quick and build a nice patina. If you buy 3-4 cheap chicken breasts and cook them in the oven until a core temperature of about 80 degrees Celcius or well done, you will have a lot of material to build a really nice and resilient patina on your Shigefusa. Slice the blade in to cover and heat it as evenly as possible. Clean it off in warm water and dry the blade carefully between each breast.

    Good luck.

    Harald.

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  8. BTW: It is the evaporation of the acidy liquid or protein liquid that makes the patina. The heat will aid in the evaporation. As far as I have seen, it is the protein that gives the blueish colour and the most resilient patina.

    Harald.

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  9. have you considered using cooked ground proteins to get a more even patina than with chicken breasts?

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  10. I have considered it, but have not come up with a process that gives me a very even result, as the parina builds almost instantly with hot protein. Especially if there is residual blood in it like a hot steak or something like that. Pleas feel free to experiment and do share your findings.

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  11. Any notes on the reactivity of the Nakiri after the forced=patina?

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  12. Actually I don't know as it is not my knife. The blade was already kuro uchi, and only the narrow ground blade road was pure metal. I had the knife in for a sharpening the other day, and it seemed like the patina was holding out pretty nicely, however, I do not know how the reactivity is as I have not used it since the patina test.

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