STROPPING A KNIFE BLADE - Sharpen like a pro

› While most people can adequately sharpen their knives with their chosen tool, the vast majority do not fully finish the process and therefore don’t get the very best from their knife. Stropping is the final step in properly sharpening a blade, and it has a significant effect on the finished edge.

Sharpening
The process of sharpening a knife brings the two edge surfaces closer to each other by working each side of the blade against the sharpening tool. Material is removed from each side by contact with the tool, which is usually stone or metal. During this process, a burr is formed at the very edge of the blade, and this has a detrimental effect on its sharpness.

What is a burr?
A burr is a tiny turned-over edge on a freshly sharpened blade, and if you magnified it, the burr would be seen as a tiny, ultra-thin, wire-like line attached to the edge. If the burr is large enough, you can feel it when you carefully draw your fingernail down the side of the blade, towards the edge. Burrs also occur if a sharp, fine blade is used particularly hard and its edge becomes ‘folded over.’ It is important to remove burrs from your blade if you want to cut smoothly and efficiently, and this is where the strop comes in.

Stropping
After you have sharpened a blade, it is very important to finish the process with stropping. A strop is a leather strap, belt, or pad that you draw the blade across, in a stroking action, with the sharpened surface of the blade flat against the leather. This action bends the burr back and forth against the leather, breaking it free. The remaining edge is now paper-thin and extremely sharp, and it will now cut much more cleanly.

Types of strop
There are a few different types of strop available, and when used correctly, they all work well. Hanging strops, such as the Rite Edge Hanging Razor Strop, are flexible strips of leather featuring a ring at the top for attaching to a wall-mounted hook and a handle at the bottom to hold and tension the strop during use. This type can often be used on both sides, and they tend to be longer than other types, allowing you to use longer strokes.
Paddle strops consist of a wooden paddle with leather affixed to each side, typically with one side being rougher than the other. The Casström Paddle Strop is a good size, with a well-designed and sized handle that keeps your hand away from the blade being worked. Rigid strops like these tend to be shorter, but they allow you to apply more pressure to the blade during use.
Field strops are smaller than other types, often pocket-sized and just a few inches long, without a handle. They typically feature two sides with different levels of leather roughness, making them portable and ideal for knife maintenance in the field.
The simplest strop is just an old leather belt, with an exposed leather grain on the back. You can attach it to a wall by the buckle on a hook, hold the loose end, and use the belt to strop your knife.

Strop pastes
Strop paste is an abrasive compound that enhances the effect of a strop, and when a small amount is applied to the leather, it helps to remove burrs while also improving the finish achieved on the blade.
Casström’s stropping pastes are available in various grits: coarse, medium, and fine. The coarse paste, containing aluminium oxide, is designed to remove burrs and provide a ‘pre-polish.’ The medium paste, also formulated with aluminium oxide, delivers an improved polish while removing finer burrs. Finally, the fine paste, made with chromium oxide, is used to fully refine and polish the blade to a bright, mirror-like finish.
A small amount of paste is rubbed onto a leather strop before you start, and the action of stropping distributes it across the surface. If there is an excessive build-up of paste, you can remove it using the spine of an old knife.

How to strop
To use a strop, place the sharpened edge of the knife against the leather and pull it along the strop in the direction of the spine (i.e., draw the blade backwards, away from the edge). Repeating this process approximately 20 times, alternating sides after each stroke, is usually sufficient to achieve the desired results. If you are using a double-sided strop, perform the process twice—first on the rougher side and then on the finer side.
It is important to control the length of your stroke, remembering that you are handling a very sharp knife. If you have ever seen a barber sharpening a cut-throat razor, they use long sweeping strokes, and doing this safely takes years of practice. You must resist the temptation to strop quickly and instead focus on doing it slowly, effectively, and safely.

Checking the results
As you strop your knife, the sharpened edge will become highly polished, which is a good indicator that you are doing it right. The whole sharpened edge should develop a mirror-like shine. If parts of it are not as highly polished, this indicates that you don’t have the whole surface in contact with the strop. If this happens, simply alter the angle of the blade slightly.
When testing the blade by cutting something, you should notice it gliding through the material much more smoothly, without any drag. A badly burred blade will drag and may even snag slightly on whatever you are cutting, but once stropped, it will glide through with almost no resistance.

Ongoing care
Once a knife has been properly sharpened and stropped, it will have reached its maximum sharpness and should only require occasional stropping, rather than frequent resharpening, to maintain its edge. This reduces the loss of metal associated with sharpening. Stropping the blade after use with just a few strokes across the leather is a surprisingly easy way to keep it in excellent condition.