Test for knife sharpness

[jyl]

Here is what seems to be the practical test for knife sharpness, per the knife geek blogs.

Take a medium ripe tomato, place heel of blade on it, hold end of handle between your thumb and forefinger and, without applying any downward pressure on the knife, draw the blade over the tomato, from heel to tip. Supposedly the knife is supposedly to slice the tomato through, just from its own weight. Repeatedly.

I tested this with my longer kitchen knives. The heavier chefs knives sliced the tomato, but the flat of the blade gets stuck on the cut tomato so they don't slice it down to the board. The lighter, thinner slicers were inconsistent, some cut and others didn't, none had enough weight to cut all the way through. They all seemed to perform worse with each successive cut.

Is this a test that only a Japanese sashimi knife, very sharp and long and very hard but also relatively weighty, can pass?. Or do I just have crummy dull cheap blades?

Try it and let meet know. Which knives pass this test?

Other tests like shaving and making see through slices seem less demanding.

[jyl]

Another test, which seems unbearably smug:

"With a knife that's sharp enough, you should be able to simply drop the tomato on the upward-facing blade and have it split neatly in two."

(Serious Eats website.)

[wdfifteen]

There are so many variables here. How thick is the tomato? How is it oriented? How heavy is the knife? How long is the knife?
I'm happy if I can draw a knife along the major diameter of a tomato for a couple of inches and break the skin without pushing hard enough to deform the tomato.

[Amail]

If the edge of the blade sticks on my thumbnail when dragging laterally then it's sharp enough for me. If it slides down the nail it's time to hone or sharpen.

[Eric Coffey]

Originally Posted by jyl

Here is what seems to be the practical test for knife sharpness, per the knife geek blogs.

Take a medium ripe tomato, place heel of blade on it, hold end of handle between your thumb and forefinger and, without applying any downward pressure on the knife, draw the blade over the tomato, from heel to tip. Supposedly the knife is supposedly to slice the tomato through, just from its own weight. Repeatedly.

That should tell you whether or not you have a sharp (enough) knife. If you are looking to get crazy/technical, then there may be too many variables. Weight/thickness/CG of blade, "ripeness" of tomato, differences in pressure/speed of the draw, etc.

Originally Posted by jyl

Another test, which seems unbearably smug:

"With a knife that's sharp enough, you should be able to simply drop the tomato on the upward-facing blade and have it split neatly in two."

(Serious Eats website.)

That is actually a better test IMO. However, you should do it with a cherry tomato (seriously). Drop it from +/- 1ft. off the deck and if it cuts clean in half, then it's super sharp. If it bounces off, you need to sharpen it.

Or, if you have a phone book handy, take a page out and gently fold it into a radius. Draw the knife across the spine/apex of the radius. If the knife will make a clean cut with little/no pressure, and not deform the page, then it's very sharp.
If you don't want to bother with finding stuff to cut, you can use your thumbnail. If you can make tiny "curly-cues" or super-thin fillets on the top surface (ridges) of your thumbnail, with no pressure, then it's very sharp. Obviously, you need to be careful with that one.

[targa911S]

A european or african tomato?

[WPOZZZ]

Originally Posted by targa911S

A european or african tomato?

Cherry. lol

[Eric Coffey]

Originally Posted by WPOZZZ

Cherry. lol

But cherry tomatoes are not migratory, so...

[wildthing]

Paper test is what I use.

[jyl]

How do those of you with sharp knives get them that way?

I'm trying to learn some new tricks.

[masraum]

Interesting stuff. The missus will probably not be impressed the next time I try all of this. Hahah.

I can hear it now "tell me why you bought $20 worth of tomatoes to cut up for no reason after you sharpened the knives."

[rusnak]

Originally Posted by jyl

How do those of you with sharp knives get them that way?

I'm trying to learn some new tricks.

I mentioned the Worksharp before. I sharpened the cheapo knives at the office to test it out. I noticed that not only were they sharp, but I believe that there is less stiction to the edge of the knife due to the curved blade tip, especially on the really thick knives.

I'll try my Wusthof chef's knife and find out if it passes your test with the Worksharp.

[masraum]

We should be shooting for this

[Eric Coffey]

Originally Posted by jyl

How do those of you with sharp knives get them that way?

I'm trying to learn some new tricks.

Really depends on the grind. Assuming a convex edge, an old neoprene mouse pad and fine-grit sandpaper works well. If it's pretty dull/chewed up, I'd start with 600-ish grit, and move up to 2000. If you want to get it crazy-sharp, you can finish off with a leather strop and polishing compound(s). There are several videos on YouTube that demonstrate the process/technique. Just search "mousepad sharpening" or "convex edge sharpening".

[wdfifteen]

I used a Worksharp. It does a good job in a hurry. If I was the only knife user in my kitchen I might get more fanatical about it, but when your wife has no qualms about cutting against a granite counter top, you have to make a choice between domestic tranquility and a good edge.
Ken Onion Edition Knife & Tool Sharpener

[intakexhaust]

I cringe at those who use steels. How the heck do they keep a consistent or factory angle?

Been quite pleased with a simple Smith honing kit and jig. You set the angle for the particular blade and dress it. If always maintained sharp by using a hone, I don't understand why one would need a machine grind and take blade material away or heat, risking change of temper.
The other issue depends on the knife application, you don't always need to take it to the fine grit. Sometimes prefer a bit of serrated edge.

BTW: Tomato test. My only Cutco knife is a the 'fishermans friend' fillet. No effort.

[Hugh R]

Some run them down, but I have a big block of Cutco kitchen knives. They aren't the sharpest, but they hold an edge for a long time that is adequate for me.



The meat cleaver is scary nice/effective. You need to have the other hand behind you!!!



I use an "Accusharp" which was recommended by someone here a few years ago. It works really well. AccuSharp Knife and Tool Sharpener 001 White with Full Length Finger Guard | eBay

[sc_rufctr]

Originally Posted by wildthing

Paper test is what I use.

+1 if you can cut paper it's sharp!

[rusnak]

Originally Posted by intakexhaust

If always maintained sharp by using a hone, I don't understand why one would need a machine grind and take blade material away or heat, risking change of temper.

Not sure what you mean by that. You'd have to heat the knife to a white hot 1000F to re-temper it, and at least 200F to anneal it. And to sharpen a knife, you are not adding material, you are taking it away. Even with a stone. In the manufacturing process, the grinding is done on a machine with a belt, and then finished on a rotating stone wheel.

[jyl]

Worked on the chef knife some more, it now slices the tomato to the board with just blade weight. No cherry tomatoes in the house, will get some. Hey, it's a salad.

Been using waterstone 6000 grit then strop, though no compound on the strop yet.