Strops are made of leather on one side, canvas or hemp on the other side. They give the the edge its ultimate polish, and redirect the microserrations after use. The abrasive silica particles in the leather give the strop its unique polishing properties.The purpose of the canvas is not certain. It may be just a coarser polish, or it may serve to increase edge temperature, facilitating the fine polish on the leather. Some barbers only use the canvas side. Juchten, a kind of Russian leather made of younger cows, is better and more durable the smooth horsehide.
In the past, strops required 'breaking in', which is the process of smoothing the strop by rubbing with a glass bottle. Later, pumice, soap and lather were used, reflecting declining craftmanship. These latter methods destroy the strop, either by increasing its surface coarseness, or by swelling and cracking the leather surface. Strops glued on wood suit straight grind blades, and hanging strops are made for hollow-grind blades. Strop sizes vary. The longest and widest ones facilitate fast and regular stropping with a large contact area between edge and strop.
The available strop-pastes are all coarser than the fine hones. However, a strop should be finer than a hone, not coarser. Therefore, the use of paste is at best irrational, at worst destructive for the edge. Paste colors are not standardized, which makes grading impossible. Black is fine, and red and green are aggressive pastes. White contains chalk, and is meant for use on the canvas or hemp side of strops. Originally, pastes were used to sharpen straight grind blades, such as the Stossmesser. They were never intended to use with hollow grind razors. The use of pastes on strops is therefore wrong. An exception is the yellow fat which serves as a canvas and leather conditioner, causing a slight drag on the edge, which improves polishing.
It is not known when to strop. Original publications report that it should be done before shaving only. Manufacturers found that the microserrations align spontaneously after a day rest as the drawings show. The malaligned teeth may break off when they get in contact with the strop. This might cause embedding of metal particles in the strop, decreasing regularity. Probably, after honing, only the leather side should be used, and in all other cases the canvas first.