In this post we will review some of the common mistakes made when sharpening knives.
The importance of sharpening
A knife is a tool designed to cut. Therefore, its form is important, but also its weight, the material it is made of, and above all, its edge.
This delicate part of the knife is what gives utility to our main tool in the kitchen. The sharper a knife is, the better it works, but the faster loses its edge, and that’s why it’s so important to know how to return it.
The day arrives. We have our knife in our hands, we have been using it in the kitchen for a while and we notice that it can not cut as before.
It does not matter if it’s an Arcos from the most economical range or a sophisticated €400 damascus knife, they all end up dull sooner or later.
As we are aware of the importance of keeping our knives in good condition to get the most out of them, we bought a sharpening stone, a support to use it, and a flattening base.
We are ready to sharpen. We already know the technique, either someone has taught us to do it or we have seen some Youtube video where they explained how to do it. However, we still do not have enough practice and we are beginning to experiment with this new technique. What are the most likely mistakes we can make?
Error 1: Do not use all the stone
When we start and learn to sharpen we still find it a strange procedure: holding the knife in a different way than usual (you hold the knife differently when sharpening one side or the other of the edge, which makes you feel a little awkward at first and without knowing where to put your hands).
We also find the movement strange and how to slide the blade on the stone.
In addition, in such a small work surface, it is likely that at some stroke the knife will get out of the stone if we go fast or do not pay much attention.
That’s why it’s normal to feel more comfortable moving the knife back and forth over the center of the stone, leaving a safety margin over the ends.
That is a problem because the shape of the stone changes. Although it is hardly noticeable at first, just as the blade of the knife wears out at every stroke, the stone also wears out as particles are removed from its surface.
Periodically it is necessary to flatten the sharpening stones, because with the continued use they acquire a ‘U’ shape, getting thinner by the center than by the borders, which makes them less effective.
If we use the entire length of the stone, passing the blade of the knife from one end to the other, we distribute the wear throughout the stone, prolong its useful life and make it easier to flatten it again.
Error 2: Not keeping a constant angle
The gesture of “accelerating the motorcycle” is the one that gives most headaches to people who start sharpening knives by hand.
It does not matter if the knife is sharpened at 12º, 15º, 17º or at another angle, the change when cutting is very small by varying two degrees up or down the angle that you apply to the edge.
The problem arises when you hold the knife at a certain angle, you start to slide it on the stone, and you forget to keep the wrist in a fixed position and move it up and down.
If you move your wrist up (you bring the spine of the knife closer to the stone), you will be giving a smaller angle to the edge and you will be removing steel from the knife blade.
But if you move your wrist down, the angle is wider (the spine moves away from the stone) and the knife scratches the stone with the edge. This usually produces a characteristic squeaky sound, which is a sign that you have just killed the edge you were working on. It is a bit confusing, but imagine the “accelerating the motorcycle” gesture.
To get the idea, the edge of a knife blade is like a triangle. At each stroke on the stone we are removing steel from the sides so that the vertex is as sharp as possible. If in a stroke we drag the vertex directly on the abrasive material, instead of ending in a point it will be rounded or flat, and therefore blunt.
In short: whatever the hand you hold the knife with, do not forget to keep the wrist fixed while sharpening.
Error 3: Not lifting the knife when sharpening the tip
One of the most difficult things when learning is to sharpen the tip of the knife. And the more curve you have at the end of the blade, the more complicated it is.
Why is this happening? Because when the blade is over the flat surface of the stone, there is a part in which they do not touch each other. From the beginning of the curve to the tip, the edge of the knife does not touch the stone.
To sharpen the tip correctly you have to lift the knife butt, the tip of the handle, straight up.
But, be careful, do not confuse with varying the angle, as we pointed out in the previous section. If you tilt the blade forward or backward the tip will still not touch the stone, and the sharpened edge will get damaged. Try to always keep your wrist in a fixed position.
To illustrate all this, we can use a Chef’s knife and a ruler.
Support the edge of the knife on the table and tilt it a little so that it is not perpendicular. Observe how yhe tip of the blade does not touch the table.
Tilt the knife back and forth to change the angle. Notice how the tip still does not touch. When sharpening do not do this movement, as we have said before, that would only ruin the edge.
Place the knife in a fixed position, as if you were going to pass it over the stone. Now lift the butt of the knife up towards the ceiling, without varying the angle between the blade and the table.
Now you can see that the blade is forming a curve and the entire surface of the edge is touching the table. That’s what we want to achieve on the stone.
Take the ruler now. Support the millimeter part on the table and tilt it a little. Now change the inclination, move it backwards and forwards without taking the millimeter part off the table (again, this is what we call varying the angle).
The whole surface of the ruler is still touching the table, right? It has not moved.
Try now to lift one end upwards, towards the ceiling. Now the rule touches the table only by the other end.
That’s what we want when lifting the handle of the knife. The curve will be higher the more we raise it.
It is difficult to understand at first, but with a little practice, and, above all, if someone teaches you how to do it, you will master it quickly.
Error 4: Not keeping your fingers on the stone
I often find this problem when teaching how to sharpen.
After explaining to my students how to hold the knife, where to put the fingers and how to place the hands, they begin to move the knife on the stone, and concentrate so much on the technique that they forget to move the left hand (or the right if they are left-handed).
The knives are always held with the dominant hand, either for cooking or for sharpening. Both are skill exercises and require the use of the most skillful hand.
Whether sharpening one side or the other of the knife, the dominant hand will always hold the handle, and the other hand will press the edge against the stone and keep the blade stable.
That’s why it’s important to put your fingers as close to the edge as possible.
Do not worry, it is very difficult to get hurt, the sharp part is in contact with the stone and if you do not separate it there will be no space for the finger to enter. You only have to be careful not to drag your fingertips several times over the stone.
Once the fingers are near the edge you have to press down to bring the blade against the stone and keep it there at every stroke.
As we are not always working the same part of the blade, we can not leave the fingers always in the same place. As we move the blade we have to move the fingers, otherwise they would not help to stabilize or press against the stone.
An easy way to remember where to put your fingers is to imagine that one hand always holds the handle of the knife and the other is always limited to be just above the stone, as if there were an area from which it could not get out.
No matter which part of the blade we are working on, the non-dominant hand will always be like the piston of a hydraulic press, placed on the area where you must press and without moving from there.
There are two exceptions: the blades that are so small that when placing the fingers we cover the whole length of the edge, or the sharpening techniques with wide movements along the whole blade (commonly called American system).
In the first case, for obvious reasons, having the whole blade covered all the time, several fingers will be pressing on the stone.
In the second, it is a similar case: a movement that must be done fluently and place the fingers in such a way that there are support points along the entire edge.
The best way to understand these cases is to see someone doing it, and, of course, take a knife and a stone and practice.
Error 5: Not using the right stone
You have a good technique, a good knife and a quality stone. You have been working with it for a while, and you see that the result is not what you expected, your knife cuts a little better than before, but not as it should.
The first thing you should do is check if there is burr or not. If you touch with your fingers and notice that part of the edge has gone to the other side, forming a small rim, then the problem is that you are not removing it correctly.
Remove the burr and test again the knife with a paper. Is it sharp now? Great, solved. Now you can move on to the next stone if you want.
The problem is when you have been sharpening for a while and the knife can not cut, you touch the edge and can not find the burr anywhere.
If your technique is correct and you are not changing the angle (remember that this gesture kills the edge and you have to avoid it at all costs), then, that is a sign that the edge of the knife was in a very bad condition.
Check the stone you are using to work. If you are using a medium grain (1,000) or fine (5,000) stone and the edge was in poor condition, you will need a lot of time to get a good finish.
For this reason, if you have to extract a lot of steel from the edge, make sure to start with the lowest grain stone you have (usually 400) and mold the edge to the desired shape until the knife can cut. Then use the following stones to polish the micro-serrated edge left by that coarse abrasive.
A common mistake of beginners is to start with a coarse stone, and move on to the next one without finishing a sharp edge, because they think they will fix it with the following stones.
The finer the stone, the more difficult it is to correct defects in the edge, so do not change to a finer grain without sharpening the edge with the current stone.