Can a knife be too sharp?

[Shalmanese]

I would say for 99% of kitchen tasks, the sharper the knife the better. But there are certain things for which I deliberately keep a range of slightly duller knives around for.

The first is slicing avocados in the shell for which I reach for the dullest, broken tipped paring knife I can find. If it's even the slightest bit of sharpness, I end up breaking through the skin of the avocado.

Breaking down chickens or legs of lamb, I have two knives, one wicked sharp and one slightly dulled. A too sharp knife makes it impossible to scrape against a bone without having the knife digging into the bone and what you end up with is small pieces of perfectly sliced off bone with your meat.

What are other tasks where you reach for the not-so-sharp knives on your rack?

[Dakki]

I've been told that you should use a duller edge mincing basil for pesto, to bring out the essential oils.

[David A. Goldfarb]

Since I've generally been keeping my knives sharper in the past year than I used to, I picked up a proper 7.5" F. Dick meat cleaver for tasks like bone splitting. Out of the box it had a rounded polished edge and convex bevel. You could press your thumb right into the edge without cutting yourself. I decided it needed to be a little sharper than that to cut through meat as well as bone, but I maintained the convex bevel, which is quite strong and resistant to chipping.

[Chris Hennes]

I keep around a dull 10" chef's knife for the express purpose of dispatching lobster (which is sorta stupid, considering how infrequently I eat lobster). I don't find that a sharp knife works any better, and I prefer the (relative) safety of a dull one when dealing with slippery thrashing sea-bugs.

[Peter the eater]

Opening paint cans -- just kidding. There are some small knives that shouldn't be too sharp. I'm thinking of butter knives, those strange-shaped cheese knives, and paring knives like the one you mention for avocado.

[beef_and_burgundy]

I use dull knives quite a lot for increasing the surface area (roughing up) of certain ingredients. The two that spring to mind are cutting potatoes for chips (french fries; rough chips turn out crispier) and a sichuan cucumber dish (where the rough surface means more of the chilli-oil dressing sticks to the cucumber).

Edited January 21, 2010 by beef_and_burgundy (log)

[SheenaGreena]

My global 8" chef's knife was way too sharp when I got it. It kept getting stuck in my wooden cutting board when I first used it. However after a while it stopped and still manages to retain it's sharpness without being TOO sharp.

[BKYLN]

I would say for 99% of kitchen tasks, the sharper the knife the better. But there are certain things for which I deliberately keep a range of slightly duller knives around for.

The first is slicing avocados in the shell for which I reach for the dullest, broken tipped paring knife I can find. If it's even the slightest bit of sharpness, I end up breaking through the skin of the avocado.

Breaking down chickens or legs of lamb, I have two knives, one wicked sharp and one slightly dulled. A too sharp knife makes it impossible to scrape against a bone without having the knife digging into the bone and what you end up with is small pieces of perfectly sliced off bone with your meat.

No offense, but both of these issues are matters of skill (or lack thereof), not having knives that are too sharp.

[scubadoo97]

Shenna, that's how you tell it's ready to be touched up. Seriously in reference to paulraphael's thread a change in technique will avoid you cutting down into your board and retain your edges better. You just don't need that much force to cut. More slicing than chopping.

[paulraphael]

Yeah, the truth is, when your Global was new, it was nowhere near as sharp as it ought to be. Factory knife edges are merely serviceable. Many of the higher end J-knives don't even come with a finished edge ... it's assumed that the user will put the kind of edge that they like on it.

If your knife was sticking in the board, that's from using way too much force ... probably from treating it like a German knife.

[Edward J]

I am ashamed to say it, but I keep my big old Henckels 10" purposely dull. I use it to hack up those 5 kg blocks of couverture, to break down 25 kg blocks of butter into smaller 1kg-ish chunks, and to cut slabbed ganache and caramels. Basically I could cut caramel with a tin-can lid, the trick is to keep the knife constantly moving with very little pressure, no need to grease the knife at all. The biggest insult to this poor knife is cutting slabbed ganache. I need a hot knife for this, not neccesarily a sharp one. Either I toss the knife in the oven for a minute or two, or "heat it up" by running a torch along the blade.

I know, I know, I know.....

I keep my trusty Victorinoxes in decent shape. My "sharpness" criteria is the humble ripe tomato: If I can get clean slices with no pressure and very little back-and-forth movement, it is "sharp".

That being said, I am a woodworker hand-tool nut, loooove spending hours gretting plane irons and chisels in shape and then dulling them all over again when I plunge them into quarter sawn oak or rock maplet

[SheenaGreena]

Yeah I was used to my heavy victorinox knife and it was a real difference switching to the much lighter japanese knife. I do prefer the new knife though (:

[saltedgreens]

I too keep a dull inox steel stamped blade for lobster fabrication. I call it my "breaker". It acts like a lightweight cleaver.

[paulraphael]

The original question begets another question: what do we mean by "sharp?"

Sharpness, in general, is a factor of the fineness of the edge (how close the bevels come to each other); the refinement of the edge (how well polished the edge is); and the geometry of the edge (how acute the bevel angles are).

There's realy never an advantage to having an edge that's not sharp in the first sense. you want the bevels to come together as closely as possible, or the knife won't cut anything well.

The refinement / polish of the edge gives you some wiggle room. For most tasks, a highly polished edge will perform better, but for some things (like cutting wet or fibrous foods) a coarse polish and toothier edge can be better. Also, only the best knife steels can really sustain a refined, polished edge. It's a waste of time trying to polish the edge on a cheap knife.

The bevel angles are the big point of compromise. Very acute angles will give the best performance, but the worst durability. For many heavier tasks, you just have to compromise performance. Lopping off the head of a salmon with super thin-edged gyuoto would be like going four-wheeling in a Ferrari. You'd have fun for a minute, but would rue the repair bills for a long time.

A couple of real world examples: my main knife, a thin gyuto, is sharpened to about 7° on a side, and is polished with a 10,000 grit stone to a mirror finish. My German chef's knife, which handles the heavy stuff, is sharpened to a bit over 20° on each side, and isn't polished at all ... the finest stone it sees is 1000 grit. You can see the little grooves in the edge without a magnifying glass.

The German knife doesn't slip through food under it's own weight, and it doesn't leave quite the same glass-smooth finish on food as the Japanese knife, but it's mighty enough to do things like lop the heads off fish and chickens, chop chocolate, and rip through poultry rib cages ... things you'd never do with a thin, delicate edge.

Edited January 25, 2010 by paulraphael (log)

[ericthered]

When my Misono (UX10) is at its sharpest and the edge is polished, it doesn't go through tomato skin as quickly as my "beater" chef's knife (Frost's), though it glides nearly effortlessly through most everything else. I speculate that the rougher edge on my "beater" knife has micro-serrations that zip though the tomato skin, but lacking a microscope this is merely a guess.

[Toliver]

The first is slicing avocados in the shell for which I reach for the dullest, broken tipped paring knife I can find. If it's even the slightest bit of sharpness, I end up breaking through the skin of the avocado.

Once I've cut open the avocado, if I am going to mash up the avocado meat, I use a regular table knife to pre-dice it in it's "shell". Because my table knives have a rounded tip (unlike, say, a steak knife), I can slice the avocado without worrying about the knife cutting through the skin and into my hand as I hold the avocado.

And yes, I do have knife skills but have found that using a table knife is my best way to deal with avocados.

[sadistick]

We keep an old chefs knife that is fairly dull for slicing pizza (much easier than a pizza cutter IMO) on the marble counter tops.

Besides that, no, a knife cannot be too sharp.

Edited January 25, 2010 by sadistick (log)

[paulraphael]

When my Misono (UX10) is at its sharpest and the edge is polished, it doesn't go through tomato skin as quickly as my "beater" chef's knife (Frost's), though it glides nearly effortlessly through most everything else. I speculate that the rougher edge on my "beater" knife has micro-serrations that zip though the tomato skin ...

How high a grit to you use for the final polish on the UX10?

My general impression is that both a toothy edge (like what's on your chef's knife and mine) and very highly polished edge will slip right through things like tomato skin. But there's a kind of nowhere land somewhere between 4000 and 8000 grit that has a lot of performance shortcomings, including sliding on tomato skin. These edges can look fairly polished, though.

[ericthered]

I have two sharpening stones, the finer is 4000 grit, so it gets pretty smooth. Sliding on the occasional tomato skin is small price to pay for an otherwise razor-sharp edge, so no serious complaints here--just a curious phenom.

[paulraphael]

It is a curious phenom ... i've noticed it a few times. The good news is that if you add another polishing stone, like 8K to 10K, that blade will probably fall through tomato skin like it's not even there.