DIY

Sharpening Knives

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A good stone and lubricant are the main tools you'll need when sharpening knives. 
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A keen edge will serve you well in the kitchen.
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Start the sharpening process with a course washita stone, moving to a medium grade.
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A stack of pennies can help you determine the correct angle to hold a blade.
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Working the blade.
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Use a fine stone for a fine edge.

Of all the time-honored skills withering in the face of
modern convenience, sharpening knives is one we can scarcely
afford to lose. As a tool-using species, it was one of our
first and most fundamental technologies. A sharp knife is
essential in controlling our environment, in separating
part A from part B without using our teeth. Once humankind
loses the ability to create and maintain a sharp edge, we
become little more than savages with clubs and
microwaves.
 

Modern slicers and dicers often regard sharpness as an
unnecessary extravagance, on par with leather seats in a
sports car. But the truth is, far from being a performance
option, a keen edge makes the difference between wielding
an efficient tool and a dangerous, uncontrollable weapon.

Knife sharpening, like taxes, is a subtractive business. In
theory, material is intentionally removed in the hopes that
some good will come of it. My own first attempts, however,
yielded nothing more than oily fingers and frustration. The
process seems deceptively simple — rub the knife
against a rock until its steel yields an edge. Eventually,
I learned that almost no skill is required at all if one
starts with the proper stone, the right lubricant, and a
certain willingness to cheat.

Viewed under high magnification, a knife edge has jagged
teeth like a saw. The trick in sharpening is to hone these
teeth until they are as small as possible while lining them
up smartly in a row. This is accomplished by first grinding
a bevel onto the knife to establish the cutting edge, then
smoothing the bevel with progressively finer stones until
the desired degree of sharpness is reached.

Sharper is not always necessarily better. The finer the
work, the sharper the knife, and the finer the stone you
will need. I read somewhere that Japanese samurai once
gauged the keenness of their swords by how many peasants in
a row they could halve with one swipe. Such an edge would
also be entirely suitable for slicing tomatoes or boning
chicken. On the other hand, such a keen blade would dull
very quickly cutting linoleum or frozen food.

My favorite sharpening stones are quarried from natural beds of
novaculite in Arkansas. The coarsest, thus fastest cutting
grade, is called washita, or soft Arkansas. It is light
gray to tan with beautiful striations of color that mark
its sedimentary beginnings. A washita stone will hone as
fine an edge as most people want. For finer polishing and
greater sharpness, a hard Arkansas stone the color and
texture of fine white marble can be used.

I admit I’m a romantic; sharpening on a beautifully colored
rock is the chief advantage of novaculite. There are also
many excellent — though less pretty — synthetic
stones. The local hardware store will likely skip the
romance and carry only these. They are often available as a
“combination” stone that sandwiches medium grit for
beveling on one side, fine grit for honing on the other.
Get the largest one you can. Trying to sharpen a long knife
on a small stone is like trying to park a Cadillac in
Manhattan.

Use water, kerosene, or special sharpening oil as a
lubricant on the stone. I keep the surface of my stone
almost submerged while sharpening. It’s impossible to use
too much. Avoid the temptation to use your favorite 10W-30
or other motor oil; it is too viscous and will make it
difficult to feel the stone under the steel, a bit like
washing your feet with your socks on. Also avoid dry
sharpening. The stone will quickly clog. I periodically use
a vegetable brush and hot soapy water to clean the metal
particles out of the stone’s pores.

Before beginning to sharpen, I use a bright light to sight
along the knife’s edge. If there is any hint of light
reflected from the cutting edge itself, the knife must be
rebeveled. For general use, this means honing a constant
24-degree angle along the entire cutting edge — 12
degrees per side. For heavy-duty cutting, increase the
angle slightly. I use a medium-grit stone for the initial
beveling to make things go faster.

There is one and only one skill in sharpening —
finding and maintaining the aforementioned angle as the
knife is drawn across the stone. Luckily for me, there is a
simple and honorable way to cheat.

Put a stack of pennies on one end of the stone, two for
every half inch of blade width. If you start the knife with
its back edge on the pennies, this will place the blade at
the correct angle. Then, bearing down hard, draw the knife
across the stone and down its length as if slicing a firm
cheese — an aged cheddar, perhaps. Concentrate. Watch
closely to make sure the knife-to-stone angle remains
constant. To maintain the correct bevel around the tip of
the knife, pivot the handle of the knife upward at the end
of each slice. Take an equal number of strokes on each side
and go slowly. This will take some patience.

As the blade sharpens, it will just perceptibly begin to
drag on the stone. If you are beveling, switch to a
fine-honing stone and repeat the process. If you are
honing, it is time to check the edge. I test the edge on my
thumbnail. If sharp, the knife will catch in the nail; if
very sharp, it can whittle small curls of nail-like wood
shavings.

As with any culturally important activity, there are
certain taboos to observe. Avoid those kitchen knife
sharpeners in which the knife is dragged through a slot.
These shred the steel at a microscopic level, leaving the
edge ragged and quick to dull. Don’t rely on a sharpening
steel instead of a stone. Using a steel may be picturesque,
with blades and elbows waving about in the air, but it is
useful only for touching up an already good edge and will
not sharpen a dull one. And don’t use a motorized grinder.
Heat buildup on a grinding wheel can draw the temper out of
steel almost instantly, ruining a good knife’s ability to
hold an edge.

The cutting edge of all human technology has always been
defined in terms of its best cutting edge: first stone,
then copper, bronze, iron, and finally steel. Now we’re
supposed to be a bit more technologically oriented, but we
still have onions to dice. So long as there is some part of
modern life that is not preportioned and shrink-wrapped, we
will need good, sharp knives. And good knives ought, now
and then, to taste a bit of oil and to feel the bite of a
good stone.