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Mon Apr 15, 2013 10:56 am

I have two Moritaka Supreme knives that I truly love. They are my sharpest and I love the shape of these knives - both Petty's. I hate the rust. These knives are so reactive that they rust just while I am using them. Everyone talks about developing a patina to help with this problem. I have had these knives over a year and I guess I don't have much patina yet. The problem has not gotten better. Anyway to create a patina o speed the process up? Thanks.

Re: Patina

Mon Apr 15, 2013 11:48 am

Two ways to force a patina; and a third which walks the edge between forced and natural.

In any case, the first thing you have to do is clean the knife thoroughly, and remove any stains. I suggest using a ScotchBrite cleaning pad, along with BKF.

BKF contains dry, powdered oxalic acid. By itself this is enough to begin a patina.

Clean the knife with a SctochBrite pad and BKF. Rinse, dry with a towel, and allow to air-dry without storing. After about 30 minutes (faster for more reactive knives, slower if the alloy has some chromium), you'll see the knife start to darken. Let it sit out for a couple of days before using.

The patina will continue to develop consistently for several weeks as long as you clean the knife without scouring it. During this period, care for the knife by rinsing or wiping the knife down with a damp rag after cutting anything which is highly reactive -- onions, raw red meat, citrus, etc. -- do not allow the damp knife to sit for more than a few minutes without drying.

Clean, after prep is completed, with mild dish soap and a sponge or soft brush.

For a couple of weeks, keep the knife out instead of in in a saya, a block, or stuck to a magnetic rack. It takes that long for a patina begun this way to develop any sort of stability.

Get a tall glass or vase, tall enough to hold the entire knife blade. Fill it with a solution made from 1/3 ordinary distilled vinegar and 2/3 water. Place the freshly cleaned blade in the solution, with the blade completely submerged, and the handle completely out. Allow the blade to soak in the solution for 6 hours. Remove the knife, rinse with water and dry thoroughly. Set the knife aside.

In a couple of hours you should see a patina begin to form; and in a couple of days it will be more or less complete. Check the knife to make sure that there are no rust spots. If there are, scour using BKF and start over.

Mix ordinary yellow mustard 50/50 with the acidulated 2:1 water:vinegar solution, described in the "acid" method. Clean and prep the knife with BKF as described above. When the knife is clean, wet one side of the blade down with some of the water/vinegar solution, and wipe it off with a paper towel. Lay the knife flat and create a pattern on the face of the knife, by painting with a brush, finger painting, with a dropper, or with spatter.

Let the knife sit for an hour. Rinse the mustard off with running water, wipe the knife down with a sponge and dry it with a paper towel. Lay the knife down with the untreated face up, and treat it as before, water/vinegar - towel dry -- mustard vinegar -- one hour rest -- clean and dry.

Like the acid version, a mustard patina won't take long to stabilize.

Continuing care:
Any time you cut something reactive, rinse or wipe the knife down with a damp rag or sponge ASAP. Do not allow a damp knife to sit for more than a couple of minutes before wiping with a towel. Clean the knife with soap and water and a soft brush or sponge IMMEDIATELY after prep. Dry thoroughly with a towel. Allow the knife at least five minutes of sitting out to finish air-drying before storing in a saya or a block.

Patinas are never fully stable. They are not absolute guarantees against rust. Check for rust every time you wash the knife. You can always remove the patina with a ScotchBrite and BKF or with a ScotchBrite and baking soda.

Regular use of baking soda is another kind of care. The knife will look like a well-used and well-loved steel tool, instead of darkening. Baking soda will help stabilize the alloy, but not as much as a dark patina. I prefer the baking soda look to any of the dark patinas, but it's a matter of taste.


Re: Patina

Fri Aug 30, 2013 8:30 am

Thanks BDL, this is very informative.

Re: Patina

Fri Aug 30, 2013 1:47 pm

WOW! That was very detailed. I will have to remember this when I finally get a good knife.

Re: Patina

Fri Aug 30, 2013 3:04 pm

Thyde - I also very much like my Supreme - petty edition, but I can't say I've had any issues with rust on this knife. I just pulled it from the drawer and there is the tiniest bit of patina below the kiruchi (sp??) finish and the blade edge, but rust? I can't say I've had that issue. Sorry to hear it. I tend to rinse mine and towel dry it if I'm not going to be using it for a few minutes at home.

Re: Patina

Sun Sep 01, 2013 7:53 am

The forced patina we do on the Richmond Addict made with 52100 is pretty simple and would also work for your Moritaka. Wash, dry, slather with mustard. Wait 20 minutes and wash and dry and you're done. You can put a drop of food safe oil on the blade (canola oil works fine) and that should be all you need.

Re: Patina

Mon Sep 02, 2013 3:56 am

JOSEPH, OTAKU <> You get nothing less from BDL; it is his way. ;)
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