Stropping, also honing, in general, is the process of stroking the edge of the sharpened knife with trailing motion, for final alignment and fine burr removal. I'm sure everyone has seen a barber honing his razor on the leather belt, at least in the movies. That is stropping, or honing. If you haven't done it already, next time, when you sharpen your knife, do it and you will be surprised with the improvement. There is another important aspect with honing, already mentioned above. Removal of the burr left by the final sharpener. That can be not so simple using other means, especially when you're using very fine abrasives. With coarser sharpeners, you can either see the bur with naked eye, or feel it with your fingertips, or both. As you go lower (in microns), which is the same as going higher on grits, that burr becomes smaller and in the end you won't see or feel it, or it'll be very hard. There's also a wire edge phenomenon, when the burr is perfectly aligned, forming sharp, but very weak edge that will be gone very quickly, once you start cutting, leaving you frustrated. So, to prevent all those things, you need deburring, which is honing/stropping. Another use of leather strops is to load or treat them with very fine abrasives, to get the ultimate sharp edge. However, that is still sharpening, thus, it will still form the burr, thus you cannot skip the stropping on the plain leather, or deburring by some other method ;)
The key point for everything written below: Use Very Little Or No Pressure. If you have done everything right up to this point, then your edge is somewhere around 1µm, may be less than that. Leather pads are softer than any stone, hence the deformation of the pad. Too much pressure and you will roll your almost perfect edge, making it dull, not sharper. In the beginning, some of the people use too little pressure, that is lifting the blade. Then, you don't get much of the effect. Good rule of the thumb would be to use the knife's own weight. Again, even though the process is still sharpening, this isn't the time when you can use pressure. Also, don't try to take a thicker edge to the loaded leather. It won't work. I mean CrO powder wont' have much of the effect on the edge that was finished with 1500 or even 3000 grit. At least, not in any reasonable time. It's just too fine and slow for that. However, if your edge was finished around 1µm-2µm, then you'll get very good results in 5 minutes or so.
One more point, which is rather obvious, but let's mention it anyway. You'll have to use separate pads for each abrasive compound. Mixing and washing don't work here. Get a dedicated pad, for each compound, then sharpen and polish away. Here on the following photo you'll see steel base and two magnetic leather pads, the green one is CrO dedicated pad, the brown/whitish is for 0.25 Diamond Crystals. Plus another leather bench for honing.
0.5µm Chromium Oxide(CrO) Loaded Leather
- CrO I've seen in two forms so far. Powder and liquid. Both are available at Dave's place - Japanese Knife Sharpening. You can use one, or another, or better yet, both of them together. Basically you should rub powder or a liquid into the leather, and in case of the liquid, let it dry. As per Dave's hint I mix them. Gives higher concentration of the CrO on the leather, hence better and faster sharpening performance. Mixing is done on the leather pad itself. I've tried both ways, first rubbing in the liquid CrO, then the powder, or put liquid CrO on the pad, then mix the powder in it and be done with it. Can't really tell the difference in the final result. Second is less messy somehow, that is in my experience. I use my fingertips to do all the rubbing and mixing. CrO isn't that difficult to wash off afterwards. The result is extremely sharp edge, with very high polish. We're way beyound hair whittling here.
0.25µm Diamond Crystal Loaded Leather
- Before this one, my finest edge was done using 0.3µm Aluminum Oxide microabrasive film. Then, Dave (yes, that Dave from Japanese Knife Sharpening) offered 0.25µm abrasive. That was something I really had to get. In theory 0.05µm isn't significant difference, but on the other hand, that 0.05µm is more than 20% difference in final edge thickness, and resulting pressure will be proportional to the area. I've been using it for a while now, and I have to say the results are very good. Improvement is noticeable, in both, final polish and sharpness. Also, one more advantage is that compared to CrO powder or liquid, diamond spray is less messy. Just shake the bottle and spray it on the pad. Which is exactly why I will get 0.5µm diamond spray as soon as it becomes available, to upgrade my experience with 0.5µm abrasives.
Plain Leather
- For stropping, I use various leather strops, bench, and handheld strops as well. Depends on the situation. You can see some of it on this picture. Large, bench strop is used mainly for larger blades, especially for the convex edged ones. The other two are for light stropping and smaller knives. Although, lately I tend to use the bench strop for all my sharpening. Another upgrade I have planned, to get a better quality magnetic leather pad from Dave. Leather itself can make a difference, especially with deburring. Plus, I don't have to keep second bench on the table.Last updated - 02/21/10