How a knife works
A sharp knife is easier to use and control, but have you ever wondered why?
A knife cuts using pressure and tearing actions created by a wedge with an edge. A sharp knife
has a wedge shape that comes to an edge with little teeth created by the sharpening material.
The knife cuts using the high concentration of pressure created by the wedge shape of the
blade. As you push the blade into the food, it crushes and splits the food. The narrower the
edge, the higher the pressure created, the better the crushing action. A dull edge creates less
concentration of pressure so you have to push harder to cut.
A knife also cuts by tearing the food as you draw the knife back and forth across the food in a
sawing motion. A close look at a sharp knife would reveal little teeth at the edge that bite and
tear into the food. As the knife goes dull, these teeth wear down and the tearing action is
reduced.
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Why a sharp knife is safer and easier to use than a dull knife
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A knife is a tool that wears during use. We cannot avoid the knife wearing, but we can
control the rate of wear.
The three primary causes of knife wear are the cutting board, handling and storage, and the
food, in that order. We can control the first two, and live with the last.
The surface you are cutting on causes the greatest wear to the edge of the knife. The wear
occurs when the knife makes contact with the surface after cutting through the food. The
harder the cutting board, the faster the wear. This is why plastic and wood cutting boards
are much better than metal pans, countertops, and china plates. The greater the force used
to cut the food, the harder the knife hits the cutting board, the greater the wear. If the knife
makes loud noises against the cutting board, try to use less pressure.
Handling and storage include using, cleaning, and storing the knife and it is the second
highest wear category. The wear is caused by the edge contacting other items. After using
the knife, put it down gently on its side, don’t toss it. When cleaning, use soapy water and
a cloth or sponge. If you need to apply pressure to clean the side of the knife, first lay the
knife flat against the side of the sink so your fingers cannot touch the edge. Storing the
knife where is does not touch other utensils will save the edge. A knife block, tray, or
protective sleeve will help tremendously.
Last is the food. Frozen food, dirty food, food in their containers, and bones cause the
greatest wear to the knife.
Research shows that you are more likely to cut yourself using a dull knife than when using
a sharp knife. Sounds wrong, but it is true.
When a knife is sharp, the wedge shape and little teeth at the edge quickly bite into the
food you are cutting. You need less force to start the cut, the knife is easier to control, and
the knife stays in place when you start to apply pressure. Using light pressure combined
with a sawing action, and a moderate grip on the food, you can quickly perform the desired
cut.
A dull knife does not work as well. The dull knife requires more pressure because it does
not bite into the food quickly. As you push the knife harder you need to hold the food tighter.
With all this extra effort the knife is harder to control and more likely to slide off the food and
into your hand. Because you are already using greater force when you cut yourself, it could
be very bad.
Why does a knife go dull?
A knife will not stay sharp forever but you can control how fast it goes dull.
Always use a plastic or wood cutting board. A cutting board is designed to give when the
knife makes contact. The harder the surface you are cutting on, the faster the knife will go
dull. Do not cut on metal pans, countertops, dinner plates, serving dishes, or china. All of
these items will dull the knife quickly.
Cut food only. You should have knives for kitchen use only and other knives for general
house use. If you use your kitchen knives to cut up cardboard boxes, trim brush, open bags
of mulch, cut rope and such, they will never stay sharp very long.
Store them properly. Avoid your knives banging into other kitchen utensils where they will
be nicked and banged around. A knife block, tray, or sleeve will avoid this.
Cut with the knife, do not scrape. After cutting up food on the cutting board, do not use the
edge of the knife to scrape the food into a bowl. Flip the knife over and use the back edge.
The edge of the knife will last 3-4 times longer doing this alone.
Use a “steel”. Misnamed a “sharpening steel”, this tool does not sharpen a knife, but keeps
it in good working order before it goes dull. It does a good job when used regularly before the
knife goes dull and is easy to use after you understand why you are using it.
Keeping a knife in good working order
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What's best for you is a balance between price, quality, your appreciation of the tool, and
overall value. You can determine best by trial and error and a little education.
The three main criteria for choosing a knife should be:
What is the best knife for me?
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If you use your knives, sooner or later they will be dull and need to sharpened. Knives have
needed sharpening for centuries and there are hundreds of tools and equipment to help
people sharpen their knives. You need to decide if you want to do the work, or pay
somebody to do the work.
I can do this. Yes, you probably can. The first thing to realize is that it will take time and
practice and more practice. You can probably put a basic working edge on your knives, but
it is a skill that must be developed. The basic principle is to grind away on each side of the
edge, using the same angle on both sides, until you come to a point. Doing this by hand
can be slow but you may have better control; whereas, using electric machinery will be
quicker and less forgiving. The key is practice, practice, practice regardless of what you are
using.
Who do I pay? There are many places to have your knives sharpened but that does not
mean they all do good work. Locations include grocery stores, gourmet shops, commercial
knife sharpeners, and some of the premium knife retailers offer knife sharpening services.
Finding a good knife sharpener will take some work, but is worth it in the long run. (That is
why you are here.)
Your knife is dull. Now what?
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The name "sharpening steel" is misleading. The metal rod does not actually sharpen a
knife, it maintains the sharp edge. Once the knife is dull, the sharpening steel is of no use.
If you could look at the edge of a sharp knife under a microscope, you would see little teeth
created by the sharpening stones used to sharpen the knife. These teeth are responsible for
the tearing action that is part of how a knife cuts.
As you use the knife, these little teeth tend to bend over. What the sharpening steel does is
straighten and put all the teeth back in line. If you do not straighten the little teeth
periodically, they will bend over and break off and the knife will get dull. The only way to
create the teeth again is to use sharpening stones and remove metal from the knife to
create a new edge.
To determine if it is time to use the sharpening steel, you can do the following. Hold a knife
with the edge upward and try to reflect light off of the edge. If the knife is sharp, there will be
no reflection because the pointed edge does not reflect light. In areas where the knife is
getting dull, you will start to see a shiny reflection. If the knife is already dull, you will see a
shiny reflection all along the edge of the knife.
What you want to do is use the sharpening steel when the knife starts to wear and the little
teeth are starting to bend over. You can tell when this is happening if you see small
reflections in areas of wear along the edge. The reflections will first start to appear on the
portions of the edge that receive the most wear.
When to use a sharpening steel
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All of us have seen chefs using a sharpening steel with hands flying and the sound of metal
singing. This is another example of somebody else making a task look simple because of a
lot of practice.
The basic principle is the same for a professional chef as it is for you. Keep in mind that you
are straightening out the little teeth along the edge that have started to bend over. This does
not require much force, but does require that the knife be held at a proper angle against the
steel. To do this, it is best to have the sharpening steel in a fixed position and then move the
knife only. The following steps will help you to use the sharpening steel properly. Be sure
your knife is clean.
How to use a sharpening steel
This page is here to provide you with some details about knives and scissors. Over the years
I asked many of these questions myself but few people in the sharpening industry actually
knew the correct answer. I hope you find this useful.
• Is it comfortable in your hand.
• Is it the right knife for the job.
• Is it reasonably sharp.
Comfort. Is the handle too big or too small for your hand, can you control the knife, how
is the weight, can I keep a firm grip when using the knife, and is the balance right. Simply
put, does the knife feel comfortable when you pick it up and use it. You are already doing
this evaluation if you have several knives at home, but only like to use a few.
Right knife for the job. You don't want to be using a 10 inch chefs knife to do the job of
a boning knife. It is important to have a variety of knives to handle different jobs and we
think that five knives is the minimum number of knives needed in your kitchen. The knives
are a paring knife, general utility knife, chefs knife, slicing knife, and a bread knife. The
first three will be used the most when preparing food.
Reasonably sharp. A knife will stay reasonably sharp if it is relatively thin, good quality
metal, and well taken care of. Care is the biggest factor in keeping a knife sharp. If
relatively thin the knife will work well, but if very thin it is easily damaged.
1. Take a look at the edge of the knife and check for reflections that indicate that the little
teeth are starting to bend over. You will be comparing the reflections before and after
using the sharpening steel.
2. Put a non-slip pad or wet cloth on your countertop. Hold the sharpening steel with the
handle straight up in the air and the end on the non-slip pad.
3. Start at the high end of the steel near the handle. Place the edge of your knife that is
closest to the handle against the side of the steel. Hold the knife at about a 20-degree
angle against the steel. (How close is a 20-degree angle? If you take the corner of a
piece of paper and fold it over twice like you were making a paper airplane, that is about
a 20 degree angle.)
4. What you are going to do is slide each side of the knife down the side of the steel
while you are pulling the knife towards you so that you make contact along the full edge
of the knife. Be sure to maintain the 20-degree angle while sliding the knife. The longer
the knife, the quicker you will need to pull the knife towards you. Apply light pressure
while sliding down the steel. Do one side of your knife and then the other. Do each side
5-10 times. Check the edge of the knife for reflections along the edge. The reflections
should be gone or at least less. Repeat as necessary; but if the reflections do not get
smaller then the knife is probably dull in those areas. Do not hit the counter with your
knife!
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Scissors work by two blades passing against each other and pinching the item to be cut. The
scissor blade is sharpened on one side only, and is flat on the other side. The two flat sides
pass against each other and the edges cut. Both the angle of the sharpened edge and the
strength of the metal it is constructed from determines how sharp the scissors are, how long
the edge will last, and what it can cut.
Do not force the scissors to cut an item. If you have to use excessive force, such as using
two hands, the scissors were probably never designed to cut that kind of item. You could
also be trying to cut too much at once.
Be sure the item you are cutting is clean. If you cut an item which is dirty, little pieces of grit
will be pinched between the blades and damage the edges. It will be like cutting little pieces
of rock.
Be sure to keep your scissors clean and dry. This is especially true after cutting wet items,
such as flowers or foodstuffs. Keeping scissors dry will avoid corrosion which can damage
the edge of the blades.
Scissors
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"Mr Leonard's Sharpening Service
was suggested to us by the J.A.
Henckel's company when we
called to enquiring about a source
for dependable maintenance of our
knife set. The service was prompt,
courteous and professional. The
knives we had sent out arrived back
well packed and in beautiful working
condition. We highly recommend Mr.
Leonard."
- Mary and Bob in New York
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