Baking Soda Polishing

I've read about Japanese chefs polishing their carbon knives with baking soda and a daikon radish at the end of the day for patina removal, polish maintenance and preventing micro-rust.

What exactly does baking soda do to the metal/patina/rust?
Does it hinder the knife if you do it on a daily basis?
Does removing the patina daily make it easier for it to rust once stored?
Do you guys advise this or do you prefer to maintain a patina to prevent further corrosion?

The baking soda is used as a gentle abrasive. Small amounts of rust can be removed and entire patina removal is possible if scrubbing is aggressive enough. If you go to big markets or restaurants in Japan you'll see people scrubbing knives with all kinds of things at closing, often removing all patina. This has less to to with knife maintenance than the general predilection for cleanliness. The Japanese (as well as many other Asian countries) consider patina dirty. If I were using every knife I have every day I might be inclined to do such a cleaning but patina is a layer of oxidization that helps to prevent further rusting so I leave it. I also like the way it looks so no harm done.

I just keep the patina, particularly on some of my less pure knives such as those with SK steel or stinky iron cladding. Otherwise I end up with staining on some types of food, which to me is not appealing.

You can use baking soda and a potato to scrub your knives, works fine. You can use mud from your finishing stone on a rag, works good too. A rust eraser is the easiest, imo.

As for storage, I don't know. I keep the patina and store my knives and have never had an issue but the back 1 inch or so of the blade has no patina and I never have issues there either. I just store in that rust inhibiting paper and cardboard.

Daily patina removal sounds like a pain in the rear.

Aogami said:

I've read about Japanese chefs polishing their carbon knives with baking soda and a daikon radish at the end of the day for patina removal, polish maintenance and preventing micro-rust.

What exactly does baking soda do to the metal/patina/rust?
Does it hinder the knife if you do it on a daily basis?
Does removing the patina daily make it easier for it to rust once stored?
Do you guys advise this or do you prefer to maintain a patina to prevent further corrosion?

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I do not like patina on my knives; nutmeg suggested automotive polishing compound which is what I use. The patina comes off with very little effort with a little dab applied to a soft rag, but the polishing compound is so fine that it does not remove any satin or kasumi finish. It is the perfect solution in my opinion and is very gentle on your knives.

On my Toyamas, I found that they would react very rapidly until I removed the patina with polishing compound; now they seem to be much more resistant to patina. I don't understand why that could be, but that is my experience.

As far as rust, I don't have any problems maintaining my knives without a patina and I live in a very humid climate. No patina, and no rust whatsoever. From my experience, a patina is not necessary to prevent rust. Just wipe your knives off after use and store in open air on a wooden magnetic rack.

I find rust erasers to be pretty useless. $5.00 buys you nearly unlimited supply of polishing compound that will keep your knives patina free.

Baking soda is a "base" (pH of 9), so it might be useful in neutralizing any residual acids from food that could harm the blade. Or else they're using it because it's cheap and available, but that's the first thing I thought of.

Edit to ad: Just looked it up, and Daikon is an alkaline vegetable, so if it's about acid reduction, then it's working together with the baking soda to that end.

Raw iron is readily oxidized into a variety of different chemicals, that's your patina. There's nothing chemically special about these iron oxides and the baking soda (sodium bicarbonate) doesn't react with them, but has hard crystals to polish them off, without being hard enough to scratch your cladding.

I've tried baking soda on potato, and it'll take off fresh patina, but won't touch the durable black patina, resulting in an uneven finish. Simichrome on a rag/paper towel is the way to go

naifu said:

I do not like patina on my knives; nutmeg suggested automotive polishing compound which is what I use. The patina comes off with very little effort with a little dab applied to a soft rag, but the polishing compound is so fine that it does not remove any satin or kasumi finish. It is the perfect solution in my opinion and is very gentle on your knives.

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Care to share this polish the name of this polishing compound that resists patina? Sounds interesting!

ob-gym said:

Care to share this polish the name of this polishing compound that resists patina? Sounds interesting!

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Turtle Wax brand polishing compound -- the white stuff, not the red rubbing compound. I use it on soft rags or on the end of a wine cork.

naifu said:

Turtle Wax brand polishing compound -- the white stuff, not the red rubbing compound. I use it on soft rags or on the end of a wine cork.

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I looked at the safety data sheet for this product. Not something I'd want to put on anything to do with food preparation.

tripleq said:

I looked at the safety data sheet for this product. Not something I'd want to put on anything to do with food preparation.

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It is water soluble. Do you think that it stays on a knife after washing with water?

naifu said:

It is water soluble. Do you think that it stays on a knife after washing with water?

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Depends on how much one has had to drink while partaking in said activity. :rofl2:

naifu said:

It is water soluble. Do you think that it stays on a knife after washing with water?

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It contains petroleum distillates. You don't really have to go further than that. In this form, petroleum distillates carries a host of warnings for short and long-term health effects such as respiratory, liver, kidney and reproductive issues. Even simple applications carries respiratory and skin absorption warnings. Whether it washes off or not is a guess. It contains waxes that may escape an initial washing or get absorbed by other parts of the knife. Petroleum distillates are not even supposed to be stored in the same area as food let alone be used to clean and polish items used for food preparation. Bottom line, it is a chemical-laden product designed for automotive applications so it is better off in the garage than on knives. There's plenty of food-safe alternatives to keep knives looking good.

Petroleum Distillates? I'm not seeing that in the safety data sheet for SKU T214A

Are you looking at the same product? I'm all for being safe rather than sorry, but I think this is OK and it will definitely wash away from a knife surface.

tripleq said:

Petroleum distillates are not even supposed to be stored in the same area as food let alone be used to clean and polish items used for food preparation. Bottom line, it is a chemical-laden product designed for automotive applications so it is better off in the garage than on knives. There's plenty of food-safe alternatives to keep knives looking good.

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I agree and would avoid using it on my knives, but it's not much different with various products used to polish kitchen utensils and flatware. I just took a quick look at the safety data sheets for Flitz, Brasso, and Tarn-X, and they're all in the "ventilate well, don't ingest" category. I guess there is a similar assumption that water rinsing is enough.

So what are the "green" alternatives? That baking soda and Daikon polish is sounding better and better...

Paraffin said:

I agree and would avoid using it on my knives, but it's not much different with various products used to polish kitchen utensils and flatware. I just took a quick look at the safety data sheets for Flitz, Brillo, and Tarn-X, and they're all in the "ventilate well, don't ingest" category. I guess there is a similar assumption that water rinsing is enough.

So what are the "green" alternatives? That baking soda and Daikon polish is sounding better and better...

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Correct me if I am wrong, but this stuff is not toxic and it does not contain petroleum distillates. I think @tripleq has misstated the toxicity of Turtle Wax Polishing Compound Paste, SKU T-214A.

naifu said:

Correct me if I am wrong, but this stuff is not toxic and it does not contain petroleum distillates. I think @tripleq has misstated the toxicity of Turtle Wax Polishing Compound Paste, SKU T-214A.

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Well, here's what one safety data sheet (PDF download link) says about "Turtle Wax Polishing Compound Light to Medium Cleaner":


Now, that's for "acute" exposure, and it's considered non-hazardous for the intended purpose of car polishing.

tripleq said:

It contains petroleum distillates. You don't really have to go further than that.

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Better sue Vaseline for putting "petroleum distillates" (petroleum jelly) in their lip balms. That category can include everything from plastic bags to gasoline, it's a meaninglessly broad category. Either way, "petroleum distillates" isn't anywhere in the safety data

naifu said:

Petroleum Distillates? I'm not seeing that in the safety data sheet for SKU T214A

Are you looking at the same product? I'm all for being safe rather than sorry, but I think this is OK and it will definitely wash away from a knife surface.

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That SDS is from Aus/NZ. It may differ from the one I was looking at. I'll try looking for it again when I'm at home and not on my phone. The sheet you pointed me to does state:

Hygene measures: Keep away from food, drink, and animal feeding stuffs. When using do not eat, drink or smoke. Wash hands prior to eating, drinking or smoking. Avoid skin and eye contact and inhalation of vapour etc....

Engineering measures: Use only in well ventilated areas.

In section 11 there are warnings for Inhalation, skin contact and Ingestion among others.

In conclusion, again, we're dealing with a chemical product that was not intended to be used anywhere near food. There are multiple safety data sheets that can vary by region, different revisions exist and formulations change. At the end of the day what you have is a guess. I wouldn't bet my health on it.

Hm, I'd be skeptical about these compounds, too. But then, I'm one of these people who don't use a microwave :whistling:

Seriously, I tried the baking soda + potato method on the Azai AS knife today... within a minute, all the patina went away and the knife is silvery and shiny again, looks like new. All the patina is completely gone, even some shallow spots of rust are completely gone after just a minute of gentle rubbing. I'm really impressed with how well this worked! The smell was NASTY though.

miggus said:

Hm, I'd be skeptical about these compounds, too. But then, I'm one of these people who don't use a microwave :whistling:

Seriously, I tried the baking soda + potato method on the Azai AS knife today... within a minute, all the patina went away and the knife is silvery and shiny again, looks like new. All the patina is completely gone, even some shallow spots of rust are completely gone after just a minute of gentle rubbing. I'm really impressed with how well this worked! The smell was NASTY though.

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Has always worked for me too.

K813zra said:

Depends on how much one has had to drink while partaking in said activity. :rofl2:

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I love this forum.

Khorax said:

I love this forum.

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+1!

Well I tried it with a potato and baking soda on the petina of my semi stainless itinomonn: nothing happened. Then I tried it with the automotive polish and paper towel: nothing happened expect maybe the rest of the knife is more shiny. I'll tell you one thing though, the baking soda did a number on my new cutting board, it's completely stained.
P.S. I'm 8 bourbon and pepsi in. Did not even cut myself.

Khorax said:

Well I tried it with a potato and baking soda on the petina of my semi stainless itinomonn: nothing happened. Then I tried it with the automotive polish and paper towel: nothing happened expect maybe the rest of the knife is more shiny. I'll tell you one thing though, the baking soda did a number on my new cutting board, it's completely stained.
P.S. I'm 8 bourbon and pepsi in. Did not even cut myself.

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I'm telling 'ya, the baking soda thing is probably all about the pH, which may be why you're getting staining. Or bad smells in the other post. Baking soda is alkaline, potato is kind-of neutral pH so it may react with the baking soda. Daikon is alkaline. I'm going to find a daikon radish (not easy in my neck of the woods) and try this, to keep the pH in the same range.

Or maybe this is all nonsense (a few too many glasses of wine here meself).

You might try with something besides a vegetable to apply the abrasive. I use the end of a wine cork or a soft rag like a t-shirt or microfiber. I used polishing compound to remove heavy and decades old patina on my Forgecraft slicer -- it works. To prevent tweaking your blade and to work the edge and tip, it is easier to hold the blade against some scrap wood.

You probably shouldn't have that raw potato around food or tools used to prepare food. [emoji23]
http://health.howstuffworks.com/food-nutrition/10-foods-you-should-never-eat-raw3.htm

Why do I get the feeling some of you would not approve of me using WD-40 to get burns / stains out of pots and skillets? It works great!

daveb said:

Why do I get the feeling some of you would not approve of me using WD-40 to get burns / stains out of pots and skillets? It works great!

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I'm alright with it. If it does not kill you -- it makes you stronger.

But seriously, materials like steel do not absorb and retain water miscible compounds. Also, something like polishing compound is not at all toxic. There is a warning for acute exposure like respirating the particles day after day or eating quantities of it, but for polishing surfaces like knives or cars occasionally, it is completely safe. If something is known to be radioactive or carcinogenic, then I would be concerned about putting it on my knives or near my food.

Put it in perspective. Most people use deodorant and shaving gel daily. This is far more toxic than occasional use of a mild abrasive compound on a knife. Toxins are everywhere, and the human body can handle a lot. Probably 99% or more or the North and South American population regularly consume GMO foods that are sprayed with Glyphosate and pesticides, or livestock that is fed such (non-organic corn and soy). That cannot be good for you right? Pesticides kill insects, and I think Glyphosate has been declared to cause cancer by California. I try my best to eat only grass fed livestock and organic sources of food, day in and day out with exception of the times I go out to eat. I'm hardly worried about polishing compound and an application of wd-40 on metal surfaces so long as it is cleaned off thoroughly.

People often go overboard with stuff like this. Do we all assume the knife makers use only non toxic materials to create and polish the knives. What anout the lacquer that is commonly applied to the blades, handles, and sayas? Do we know stones have only non toxic materials? What about natural stones? God only know what could be in there. What about that plastic cutting board? What about that teflon pan? What about the sugar we all eat? I would contend that the sugar in most people's diet is way more toxic than any polishing compound residue that won't wash off the blade with soap and water.

I realize that we're constantly exposed to compounds the body can shrug off, as long as the exposure isn't acute, like directly eating the stuff. I'm far from being one of those who sees toxins everywhere in the environment. On the other hand, I don't think it's going overboard to choose a more "green" method if it works just as well as a commercial chemical product. Probably cheaper too, for something like radish + baking soda.

One other consideration, which might not apply to everyone, is that I live in a house built in the late 1800's. There is a mix of new PVC plumbing directly under the latest kitchen remodel, plus a bunch of creaky vintage copper and iron pipes downstream from there. So I'm careful about what goes down the sink. Not just for environmental reasons, although there is a bit of that. Mainly I don't trust the antique plumbing to handle a steady diet of aggressive chemicals.