knife question for Stig

[Ken S]

Stig,

I notice in your video with Stumpy and Mike a short scene where a chef's knife effortlessly slices a micro thin slice out of a tomato. The tomato is just sitting on a cutting board with no other support. That's pretty fancy shootin', partner.

I know that cutting things like tomatoes benefit from having a bit of tooth on the blade. Did you polish that blade on the leather honing wheel? Japanese wheel?

Ken

[grepper]

Ken, while not answering your question to Stig and not trying to hijack this thread , I thought you might be interested in some testing I did cutting tomatoes with knives sharpened with more and less coarse abrasives, producing a more or less "toothy" edge.  As I recall, I had 4 or 5 knives sharpened ranging from right off the Tormek with a coarse stone, to very highly polished blades produced using 3M Microfinishing Film and super fine polishing abrasives to about 12,000 grit.

A couple of years ago we had a very hot, dry summer.  For whatever reason, it was not a good year for tomatoes.  They didn't ripen well, and would start to rot from the inside out, leaving a thin, smooth but tough skin, with very soft, watery, rotten guck in the middle.  Sounds delicious, doesn't it?

While they tasted like crap, they were excellent specimens for testing knife sharpness and edge grinds from rough to polished. 

The most excellent and telling subjects were tomatoes that were just starting to collapse, leaking rotten yuck, but were still more or less round without skin degradation.  When attempting to cut these stinking blobs, it took very little pressure to squish the tomato while trying to penetrate the skin with the knife.  So I picked up a bunch that were decomposing on the ground and proceeded to test.

What I found was that a polished edge can cut even a very soft in the middle, basically rotten tomato with a smooth, tough skin.  But..., it had to be really, really, sharp.  I emphasize; really, very sharp. Approaching razor blade sharpness.  I used a new safety razor blade for comparison.  If the knife was not super sharp, even with a careful sawing motion the blade would ride on the skin and the tomato would collapse and ooze out its insides before cutting the skin.  If however there was even a tiny break in the skin, the blade would slice most excellently.  These blades were so sharp, that even gently bumping against the finger would cause epidermal leaking.  They were most excellent at slicing human skin!  They would work great for sashimi or any other raw flesh, leaving a very clean cut.  I actually shaved with one and was surprised how well it worked. (Not recommended).

While the Tormek can produce knives that sharp, I found that degree of sharpness didn't last long with normal use.  As soon as the super sharpness was history, the polished blades became generally less useful.  The still performed well for chop cutting, but anything with a smooth surface became problematic.  It was evident even on vegetables like broccoli with a hard, smooth skin.

Without wishing to entertain the argument of longevity vs toothy/smooth edges, from my experience at least, a moderately toothy blade is generally more useful in the kitchen, and the edge lasts longer for all around, general, cutting.

I would be interested to know if anyone else has conducted the same tests, and how those results compare.   

[Ken S]

Outstanding post, Grepper. Scholarly, practical, and not without a dose of humor.

Your "epidermal leaking" reminds me of something I have observed with Tormek sharpened knives: When dropped, they always land on the tips and stick into the kitchen laminate or dinette hardwood....oops....Fortunately this has never happened when my wife is around. I have also experience epidermal leakage. As an old first aid instructor, I know that such a clean incision tends to be self cleaning with the leaking.

Ken

[stevebot]

Thanks Grepper,
I have seen the same results. I used to give every knife a polished edge until a customer showed me that while it shaved it slid on a tomato skin. I gave that knife a couple of swipes on a ceramic steel and it sliced like it was meant to. We use that same ceramic steel in our kitchen to touch up between sharpenings and I now finish 90% of my knives with a 1500 grit ceramic wheel. High-end Japanese knives with 15% bevels I still polish.

[grepper]

Thanks for posting your tomato experience Steve!  Those pesky tomato skins, especially with a nice squishy tomato, are great for demonstrating what a little "tooth" can do for you.  Oddly, hard, shiny broccoli skin does it to. 

I find it interesting that you don't have the same problem @ 1500 grit.  I would think that still would produce a pretty polished edge.

Just for grins, the other day I sharpened a knife on a 150 grit belt.  The belt was not new, so I suspect it was more like 200 grit, but still pretty coarse.  After stropping, it was very sharp.  It chopped cut paper against the grain easily and shaved hair.  You know... sharp.  It's winter so I didn't happen to have any tomatoes, especially gushy ones, but it hung nicely on the edge of onion skin and garlic, and produced clean, thin cuts.  It seemed a perfect amount of tooth for a kitchen knife.

I should have taken the time to pitch the thing under the microscope to check out exactly what the edge was like, and I'm interested in how it will hold up.  I'm not fully convinced that for general purpose kitchen knives, anything over about 225-325 grit is really advantageous.   Note "general purpose".  Obviously there are times when a polished edge is preferable. 

Have you every experimented with edges sharpened with a fairly coarse grit?  It's a big time saver, and I found the results somewhat surprising. 

I'll have to do the same thing again and have a little look-see at the edge right after sharpening and then again after some use.

Anyone else do some experimenting along these lines?

[Ken S]

At the risk of being boringly practical, all the gee wiz micro slices of tomatoes were stunning, however, for a sandwich, I prefer just an ordinary slice, which can be cut with a reasonably sharp knife by holding the tomato.

Ken

[grepper]

There you go again Ken, being practical!

[Ken S]

Sorry, Grepper. It may be a genetic problem. I am half New England Yankee and three percent Neanderthal. (The Neanderthal heritage was confirmed in a DNA test..........And , I have had a lifelong partiality to swiss cheese and tomato sandwiches.

Ken

[grepper]

And with your history of phone installs Ken, I'm sure that you will appreciate that I think your advice about holding the tomato is a good tip and rings true.

[Elden]

Interesting take on the durability of the edge.

[Ken S]

This one upmanship over tomato microtomes reminds me of the comment Jeff and I bounced back and forth, "How many angels can dance on the head of a pin?"

Ken

ps At one time, answering this question incorrectly could get a person in serious trouble with the Inquisition!

[Mike Fairleigh]

Ever since I was a kid, I've labored under the impression that slicing tomatoes was only impressive if the knife was first used to cut through a tail pipe.

(For those outside the U.S., we had a famously annoying infomercial for "Japanese Ginsu knives" wherein the knife was used to cut an exhaust system in two, followed by slicing a tomato with scalpel-like ease.  Realistically, the Pocket Fisherman was probably more useful, even today, as part of a prepper's go-kit.)

[Stickan]

Hi,
I did polish the edge, as I always do, but a little burr would have made it even easier. I did not use the japanese wheel on that knife.
But!!  A polished edge will stay sharp longer than if the burr is left on the edge.
I always polish with the honing wheel and it get´s as sharp as a new knife, sometimes I get even a sharper knife then it was new.
Once in a while I do even use the Japanese stone even If I know that I really don´t need to. But my knifes get´s unnecessary sharp and good looking then 
But I do know that most knife users gets really impressed by the sharpness the regular stone and honingwheel give.

Stig

[Ken S]

Stig,

My wife has the strangest ideas. She even suggested that I might actuall use my beautifully razor sharpened knives in the kitchen where they might become dull. Perish the thought!

Ken

ps Mike, maybe that is the secret of the smoky flavor in sandwiches.........

[tylers]

OK, Gentlemen,
what are you all polishing the  edge with? Steve referred to a 1500 grit wheel. What else? Being a 'newbie' I know I am probably asking repetative and stupid questions, but.....
As they say in the demotivators    " there are no stupid questions, but there are plenty of inquisitive idiots".
T