How Acidic Food affects Sharpness

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Another great article. I've suspected that corrosion resistance played a small part in edge holding, but I did not think it would be such a measurable effect. Good experimental design to be able to demonstrate the differences.
 
Very interesting. I wonder how something like AS with some tungsten carbides would fare. Personal experience suggests it might hold an edge better than simple carbon steel while cutting acidic foods, but without testing it's easy to fool yourself.
 
CoteRotie said:
Very interesting. I wonder how something like AS with some tungsten carbides would fare. Personal experience suggests it might hold an edge better than simple carbon steel while cutting acidic foods, but without testing it's easy to fool yourself.
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The carbides would be unlikely to affect corrosion very much. Chromium in solution to produce a passive film is the main controlling factor.
 
Great article.
I hope you follow up on your summary and do some more tests in this area.
It also might worse considering to add some stress into the mixture. This is because when prepping the food the edge bangs against the cutting board and it might account for something.
 
Ruso said:
Great article.
I hope you follow up on your summary and do some more tests in this area.
It also might worse considering to add some stress into the mixture. This is because when prepping the food the edge bangs against the cutting board and it might account for something.
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+1 on the idea of testing subtle difference, eg white and blue steel, AS etc
+1 on some kind of edge stability testing.

Does hardness/brittleness co-vary with accelerated degradation, either positive or negativley?

If there is some structural weakening, would be good to suss that out...somehow or another.

Have no idea if this is easy or hard to do experimentally, however.
 
Larrin said:
I did a small study on the effect of acidic food on sharpness. Is a carbon steel knife going to do okay with lemon juice?

https://knifesteelnerds.com/2019/01/21/does-acidic-food-affect-edge-retention/
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Thanks for taking the time to do this!

Intuitively, the result makes sense. If I picture a knife that, by degrees, goes from perfect to a little bit corroded, to a lot corroded, to completely rusted out, it's obvious that the completely rusted version won't cut. Accordingly, I would expect sharpness to continually degrade along that progression.

I've seen carbon steel knives that were used to cut acidic food develop corrosion spots within literally minutes. Feeling those spots reveals a rougher surface texture. If one of those spots happens to be at the blade edge, it'll be just as rough there, gradually destroying the apex.

The obsessive wiping of knives that one sees from Japanese chefs is obviously not just to keep the knife looking pretty…
 
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Thanks for this! Very interesting.

It helps reinforce my habit of reaching for my semi-stainless Sukenari 165mm HAP40 petty when slicing lemons and limes instead of a carbon knife, although I seldom cut more than a few at a time, not like a pro kitchen. I might blast through a bunch of lemons when making salted lemon preserves once a year, or more frequently cutting up a bunch of oranges or tangerines for juicing. But in home kitchen use like this, I'm not really sure that's enough to be worth switching from carbon to a semi-stainless, at that rate of use. It's more a question of just knowing I'm using the right tool for the job.

And it gives me an excuse to keep this HAP40 petty knife in the drawer, when it's been mostly superseded by carbon knives. Any excuse to keep a knife is a good excuse. :)
 
It coincides with my own experience when forcing a patina and forgetting to wipe the very edge. The result is a much coarser one.
Interesting that with stainless the deterioration seems to stop after the loss of the fresh from the stones feeling, and the edge still being quite usable. Always tried to convince stainless users to treat at least the edge as if it was a carbon one. Will reconsider that.
 
Great article and very well done experiment. I would be interested to see how having super sharp knives would affect the results. My thinking is that Stainless relies on the reaction of the Chromium to make a hard passive layer a few atoms deep to protect it from corrosion. Effectively its own corrosion protects it from corroding further. This is possibly what caused the initial slight drop in sharpness in the stainless blade. I wonder if a super sharp edge would mean that the few atoms of chromium reaction becomes a relatively larger effect on sharpness so would show a bigger drop off.... Just food for thought!
 
What do you think about some SEM photomicrographs of the edges before and after exposure to the corrosive agent? Possible?
 
pennman said:
What do you think about some SEM photomicrographs of the edges before and after exposure to the corrosive agent? Possible?
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Probably not going to happen. We will see.
 
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