How to mirror polish a knife by hand

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Well, today we are discussing how to mirror polish a knife by hand while sitting at home.

Among the basic maintenance tasks of a knife, polishing is on the first order, since the use causes wear, scratching or sometimes even the appearance of stains or rust on our knives.

However deteriorated it may seem to us, a quality metal knife can always be polished and restore its luster, sometimes incredibly, with a specific treatment in each case.

Many have asked how to polish a knife blade. We are going to discuss methods of polishing a knife applies not just to a kitchen knife but to every type of knife.

The first thing to make clear is that polishing and sharpening knives are very different things, although we know that some people confuse the terms. If that is the case, we will leave a link to our post where we explain how to sharpen knives in different ways.


What is polishing?

Polishing is one of the aesthetic finishes that a knife blade can have. A polished blade has a shiny, mirror-like surface.

how to mirror polish a knife

What materials do we need?

We can polish a knife either by hand or by machine. Hand polishes often leave a finer, more polished finish, but machine polishes are quick, easy, and inexpensive.

In both cases, the principle is the same. We use an abrasive paste applied to a support and rub the metal of the sheet with it.

The abrasive can be any, as long as it is fine-grained. Some options are chromium III oxide, aluminum oxide, silicon carbide, or diamond pastes.

For machine polishing, the abrasive presented in the form of hard wax bars are usually used. For hand polishing, they can be used in cream, soft paste, liquid, or powder presentations.

How to polish a rusty knife

We wanted to show the possibilities in terms of polishing a knife starting with an extreme case. So it is a clear idea that virtually any unpolished knife or very deteriorated in appearance, provided that the metal is worth it, can be recovered.

As we can see, even in the extreme of having to polish a rusty knife to the point of looking completely orange, and dull, the procedure starts with:

  • Soaking the rusted metal in white vinegar for 48 hours. It will be less time in case there is not so much rust (we will see it in another video below).
  • Wash, and scrape with a wire brush. In this way, we will be able to remove the thickest layer of rust, and the rest of the polishing of the knife can be done by hand, with sandpaper, or more comfortably through an electric sander.

The rest of the process of roughing, sharpening and complete regeneration of the knife is a pleasure to watch for anyone who considers himself a knife lover. If it is not relevant we can skip it if we do not want to spend more time than necessary.

How to polish a carbon steel knife at home with vinegar

One of the most frequent queries we have encountered is the one that refers to the polishing of carbon steel knives, as this type of metal is very susceptible to rust (a price to pay for its great cutting quality).

Check this short video. It is a very practical and effective method to polish carbon steel knives by hand with something as simple as vinegar and aluminum foil.

As explained in the video, this homemade method for polishing carbon steel knives consists of the following:

  • Impregnate with vinegar and let stand for about 5 minutes.
  • Remove the vinegar with a cotton swab and repeat the operation a couple of times.
  • Make a ball with aluminum foil, and pass the ball soaked in vinegar on both sides of the blade repeatedly, as if we were sanding it.

In the beginning, we will see that the vinegar comes out orange, due to the detachment of the most superficial remains of oxide. And in the second phase, the vinegar will take a grayish color, due to the detachment of the patina and the reaction of the aluminum itself with the vinegar.

  • Finally, we will wrap the sheet in a napkin completely soaked with hot vinegar, and we will leave it for 45 minutes and then clean it well with a cloth or piece of cotton. In this way, we will obtain a patina that will help the carbon steel to prevent rust.

We can simplify the carbon steel knife polishing process. Rub the knife blade with an aluminum foil ball after keeping it wrapped with a vinegar-soaked napkin for 45 minutes as mentioned in the last step.

Learn how to sharpen a ceramic knife.

How to polish a knife with sandpaper

Obviously, the use of power tools or even industrial tools is the easiest way to polish knives and leave them like new ones. But most of you come here wondering how to polish a knife by hand. Be it a kitchen, or hunting knives that you take to the field, can lose some of their lusters.

Well, if you ask how to polish a scratched knife by hand at home, we always recommend the simplest and most effective method. If there is no rust, we will not need to use vinegar, so we will polish the knife with sandpaper.

To summarize, the process of polishing knives by hand would consist of:

  • Add a small amount of oil or silicone to the face of the knife blade we are going to work on, and spread.
  • Place a 100 grit sandpaper on the contour of a rectangle of wood, and polish the knife by hand.
  • Repeat this operation passing to consecutively finer sandpaper, until finishing with a 1200 grit sandpaper, and doing so on both sides of the blade.

In this way, in the end, we will obtain a mirror-finished polished knife blade. It does not take more than an hour.

Of course, if we do not have a good set of sandpaper of different grains, something indispensable for anyone who is considering polishing knives by hand, the old-fashioned way, with care.

If you are wondering how to polish handmade knives, keep in mind that these do not require any different treatment. However, avoid exposing the wooden handle to vinegar to prevent losing shine.

polishing a knife like a mirror
How to mirror polish a knife

One thing to keep in mind

A knife with a polished blade has two major drawbacks.

The first is aesthetic. The polishing of the blade is easily scratched by the daily use of the knife, even if we use it correctly.

Cleaning the knife with a cloth, cutting through the food or keeping it in its sheath are actions that leave small marks on the steel. In other types of finishes, these marks are better hidden, but in a polished blade that shines like a mirror, any small scratch immediately attracts attention.

If the marks are shallow they can be removed with a bit of fine polishing paste and a piece of cloth.

However, if they are deeper, a more abrasive paste will be needed. And if that is not enough, you will have to repeat the process from scratch, starting with wet sandpaper.

This type of finish is very pleasing to the eye, but it is laborious to maintain.

The second big problem is that the surface of a polished blade is very little slippery for food. Knife leaves with other types of finishes there are small spaces (in the form of grooves, scratches, hammering, etc.) between the body of the leaf and the food. These holes facilitate the entry of air and help the cut food to detach from the blade.

In a polished finish, all those blemishes and voids are eliminated. To achieve the reflective finish, it is necessary to leave the surface as smooth and continuous as possible. That is why the last steps are done by applying extremely fine pastes. As there are no gaps through which the air enters, what we cut with the knife will tend to stick to the blade.

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