Maximizing Edge Retention – What CATRA Reveals about the Optimum Edge

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Larrin said:
But doing both at a time would leave you unable to determine the individual effects. If acid alone didn’t affect the edge a second experiment could be cutting some fixed material (such as rope as you said) both with and without the acid. But the wear from the rope may overwhelm the effect of corrosion.
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Agreed.
I guess you'd have to have 3 arms: acid only, abrasion only and acid plus abrasion in order to tease out the differences.
 
To make it simpler you could just do simple high carbon and acid like Larrin suggested. If there wasn't enough of an effect, you could reasonably infer if acid is the cause.
 
Yes it would be reasonable to start with a simple carbon steel for a baseline. Then compare with stainless, for example.
 
Nemo said:
Agreed.
I guess you'd have to have 3 arms: acid only, abrasion only and acid plus abrasion in order to tease out the differences.
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I'm still wearing my skeptic's hat about a purely chemical reaction from tomato acidity causing any change in cutting action over a period of a few hours. That would be a powerful change in the metal of the blade edge on a microscopic level. It would be the first thing to test, because we all sharpen differently with different amounts of "tooth" that will affect cutting veg.

So, expose the blade edge to tomato juice over a few hours and then take a series of electron micrographs at different magnifications, like those at the scienceofsharp web site. Preferably with a few different metal types. Compare that to micrographs of the blade edge before acid exposure. This would demonstrate whether acidic foods alone are a factor.

Maybe someone can talk that guy at scienceofsharp into testing it, or a phase 2 of the OP article. :)
 
Would be simple to do a test cut with a freshly sharpened knife and then soak the knife in tomato juice and then repeat the test cut to check for comparison.

The next question would be does the combination of the acid and the cutting through the fiber of the tomato combined, even as delicate as it is, make a difference. Acid and light friction....
 
Putting a knife in a glass of lemon or tomato juice & testing it on equal tomatoes or lemons before and after would be a test. I prefer the real world where it counts that's what knives are for cutting food.

Take a case of tomatoes or lemons split it in half equal to each cutter. Slice & dice tomatoes or cut the lemons into wedges. I'll take a thin carbon laser, you take the stainless knife of your choice. If corrosion guys are right esp. a super thin edged carbon will dull in the act of cutting and quit performance. Save one lemon or tomato at end to see how each cuts.

As said agreed with the findings of this test even though it was cutting cards. A medium grit cut over 1000 cards and knife geometry was most important factor. A toothy 1K edge is best for tomatoes, bell peppers lots of food and keeps working for hours. Polished edges do not work as well for lots of prep. unless it is sushi or sashimi.
 
The acid just weakens the (apex) metal a tiny amount,
its the board contact that kills the (now weakened) edge....



ALso, with tomatoes, I swear the seeds don't help :(
those seeds between your board...and the knife
 
There is fibrous material in side the tomato, besides the seeds,
of course so this makes some sense...
 
A microscope isn’t necessary if using a sensitive sharpness tester using a finely sharpened edge. Any change would show up.
 
Larrin said:
A microscope isn’t necessary if using a sensitive sharpness tester using a finely sharpened edge. Any change would show up.
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I agree that a sharpness test under controlled (and repeatable) conditions would show whether tomato acid reduces sharpness. I hope someone can do that, and put this idea to rest one way or another.

Regarding the microscope... I'm still curious about the proposed mechanism for weakening the edge. Tomatoes have a very mild level of acidity, compared to the industrial acids that we know can etch and physically change metals. An electron micrograph would show pitting or other changes that could reduce cutting ability.
 
Paraffin said:
I agree that a sharpness test under controlled (and repeatable) conditions would show whether tomato acid reduces sharpness. I hope someone can do that, and put this idea to rest one way or another.

Regarding the microscope... I'm still curious about the proposed mechanism for weakening the edge. Tomatoes have a very mild level of acidity, compared to the industrial acids that we know can etch and physically change metals. An electron micrograph would show pitting or other changes that could reduce cutting ability.
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A microscope would be great for observing how the edge was corroded for sure.
This website lists food acidity: http://www.webpal.org/SAFE/aaarecovery/2_food_storage/Processing/lacf-phs.htm

It looks like tomatoes are around 4.5 pH, though apples, oranges, and lemons are all more acidic.
 
Most seafood is high on pH level. You acid dulling knives worry dudes better go over to Tsukiji market and tell those poor dumb Japanese to stop using their carbon knives to clean all that fish right now. Get Sushi chefs to ditch their carbon Yanagiba's and Deba's and get stainless.

If you are cutting tomatoes in your hand it's a good thing your knife is not that sharp.
 
Larrin said:
A microscope would be great for observing how the edge was corroded for sure.
This website lists food acidity: http://www.webpal.org/SAFE/aaarecovery/2_food_storage/Processing/lacf-phs.htm

It looks like tomatoes are around 4.5 pH, though apples, oranges, and lemons are all more acidic.
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Yeah, that's why I'm still skeptical. I've never heard anyone say that cutting apples will dull a blade more quickly than other produce, and they're more acidic than tomatoes. Not that I'm doubting anyone's personal experience, but it could be something other than a fairly mild low PH that's affecting the edge that quickly.
 
Keith Sinclair said:
Most seafood is high on pH level. You acid dulling knives worry dudes better go over to Tsukiji market and tell those poor dumb Japanese to stop using their carbon knives to clean all that fish right now. Get Sushi chefs to ditch their carbon Yanagiba's and Deba's and get stainless.

If you are cutting tomatoes in your hand it's a good thing your knife is not that sharp.
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On the list the seafood looks like its mostly close to neutral (7).
 
Larrin said:
I found this: http://www.edgeonup.com/Video PT50B Oxidation LR.mp4
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I can't really follow how the machine works :(

PT50B... This instrument is the direct replacement for our original PT50 which is currently at work throughout the US and 17 countries world-wide. With a faster processor and simpler operation the PT50B is the workhorse instrument for professional sharpeners, knife enthusiasts and woodworkers. The PT50B has a steel measurement platform and delivers 5 grams of resolution with a 1 year warranty. 5 grams of resolution is more than adequate for all the sharpening room discoveries you will soon be making! The PT50B includes a knife fulcrum and our Aluminum Test Fixture. The PT50B can easily use our Disposable Clip system if purchased separately. The clip system is not only versatile, super fast and simple but a real advantage for anyone with diminished eyesight and/or hand and finger dexterity.
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some other crazy products, here...

http://edgeonup.com/Analog Testers.html
 
The machine is a scale with an aluminum block on top that holds taut a thread. You press the blade onto the thread until it cuts through. The maximum weight applied is displayed on the scale.
 
Ok, I was trying to understand that ...
thanks for making it more clear.
 
Larrin said:
A microscope would be great for observing how the edge was corroded for sure.
This website lists food acidity: http://www.webpal.org/SAFE/aaarecovery/2_food_storage/Processing/lacf-phs.htm

It looks like tomatoes are around 4.5 pH, though apples, oranges, and lemons are all more acidic.
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Paraffin said:
Yeah, that's why I'm still skeptical. I've never heard anyone say that cutting apples will dull a blade more quickly than other produce, and they're more acidic than tomatoes. Not that I'm doubting anyone's personal experience, but it could be something other than a fairly mild low PH that's affecting the edge that quickly.
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I've never cut apples, oranges or lemons for a couple hours at a time to know how they affect edges. Only tomatoes, that's why I only mention them.
All the others may be as bad or worse but I don't have the first hand knowledge to know.
 
are you using a cut glove? why cut them up in hand
if we are talking peeled tomatoes, sounds slippery ;)
 
I'm dropping them directly into a canning jar through a funnel as I cut them. I used a cut glove when I first started cutting like this but haven't used one in years. I use only the slightest of a slicing motion, more just simply a light push through the tomato. It drops through very easy and it's really not that hard to get a feel for when to stop before cutting yourself as the tomato separates.
I can tell when the edge of the knife is starting to degrade because the gets harder to push through the tomato so I stop and strop and start again and the edge difference is obvious.
 
OK, I was picturing diced tomatoes done in hand and cringing...:lol2:
 
Depending on the size of the tomato I cut it into anywhere from four to eight pieces as I can them, turning the tomato in hand as I cut. I"m not dicing them into 1/2" pieces or anything crazy like that in hand. I don't always go completely through the tomato either but by the time they get through the canning process they have come completely apart.
 
K813zra said:
Like that fellow that dices the onion in hand on youtube? There was a link around here awhile back.
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[video=youtube;3wlgNYVRN7Q]https://www.youtube.com/watch?v=3wlgNYVRN7Q[/video]
 
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