Thread: Razor Info From Arthur Boon part-2.

HONING AND GRINDING You can learn to sharpen any knife on a stone, and if you have experience, or use the right sharpening system you will get very good results.
The principle of grinding any knife is restoring the gross shape of a blade according to it's grind-type (hollow, flat, or transitions); this is mostly done with machines such as grinding wheels. Grinding does not sharpen a knife.
The principle of honing is to create a good cutting edge angle and the blade part directly adjacent to it, the relief. The relief is created by honing with a secondary angle on a stone until a burr appears, and subsequently create the primary angle (this is the cutting angle, which is somewhat greater than the secondary angle, but both under 25 degrees) to remove the burr. The relief/secondary/primary angle principle makes the blade more resistant for less than delicate use.
The primary/secondary angle/relief principle does not hold for straight razors. The cutting edge of about 15 degrees (primary angle) is followed by a biconcave (hollow) part, and a ridge, respectively. This unity keeps the edge ultra thin during its life despite honing and stropping, and on the other hand supplies the blade with enough rigidity because of the ridge. Also, the absence of a relief with a secondary angle, clears the cutting edge while honing with the back resting on the hone surface. The back serves as a guide which conserves the primary cutting angle under all circumstances and the same applies to the strop. This implies that the primary/secondary angle story is not valid for =BC, 1/2, =BE and 1/1 hollow ground straight razors. In fact, the ridge and the hollow grind part between ridge and edge, are some kind of relief-substitute, which is not a compromise at all, because it's function is delicate without requiring any force.
It has been unclear why and when a blade should be re-hollow ground. The German book referenced below, however, states that only extreme abuse is a reason to restore the architecture with a grinder. As this results in blade reduction, the back must be reduced accordingly to preserve the correct cutting angle. If you care for the blade as a 'good house-father' self-honing and stropping is enough. If the damage is nothing more than just touching the edge with your nail, causing a little local flattening of the edge, then honing will be sufficient. On the other hand, when dropping causes a defect in the edge you won't get rid of it with honing, and this needs repare with a hollow grinder.
At DOVO, the grinding is done by moving the blade between two wheels. After the grinding, they machine-hone on the side of a moving wheel, in the direction (!) of the edge and not towards it, untill a burr appears. This is done with the cutting angle, so with the back just not (to prevent damage to the back) touching the wheel. On a second, finer, honing wheel the burr is removed, again with the same cutting angle determined by the back. Water is used on both wheels. Then the honing starts, on a very fine Belgian Old Rock and succesively on a even finer one, called Escher waterstone, type Rasierstube. The Old Rock is also called Belgian oil stone, but Dovo uses water. Razor Edge Systems suggests that any liquid, whether oil or water, creates a sludge with the metal and stone particles, rounding off the edge, thus causing blunting. This contradicts with the observation of German smiths, that a hone performs best when you create that sludge before starting, by rubbing the hone with a small stone and water. They state that ' especially when the sludge is present, the edge will be extremely polished and sharp'.
The last hone in the process, the Escher waterstone, even comes with a separate rubbing stone, and a manual how to create the sludge. At DOVO, honing is done with circular movements, manually, with impressive speed. First on one side, and then the other, so not alternating. The result is obvious: the hones wear off irregularly, causing a concave surface. Then they need a new hone. The reason for doing so is time-efficiency. For the consumer who wants the hone to serve for an unlimited period of time, the following alternating linear method is better. Lay the blade completely flat on the stone and push it forward into the direction of the cutting edge, and slightly diagonally in the horizontal plane over the stone (the reason for that is to hone the complete cutting edge). Then turn the knife over the back without lifting it from the stone. Never turn over the edge, this will blunt the blade. Then repeat into the other direction; repeat this process about 10 or 20 times.
Some things are critical in order to get a sharp edge: the first is to ensure that the razor lays completely flat, so that the edge and the back touch the stone surface. This is to keep the exact required angle of the edge. The second is, that the razor remains flat on the stone during the movement. If you don't have experience, you will only succeed doing so if you hone extremely slow, and study the process carefully. Only then you will be able to observe that during the stroke, the edge or the back will tend to lift from the stone a millimeter on one side which you must correct, which is only possible when honing extremely slowly. Here, speed does not add up to better results, not even in experienced hands.This will give excellent results even for beginners (I tried it that way, with already immediate perfect results).
The third is, that you don't press on the blade while honing: the weight of the blade is enough. Pressing will deform the angle. Hones should be large, because the surface is then completely in contact with the cutting edge; any damage or irregularities to the sides of the stone are then less critical because you will not reach them.
You notice that when you carefully make a cutting movement over your thumbnail; any knick feels like a sudden obstacle. It also gets damaged when you strop the wrong way, with the wrong paste, or when the razor gets into contact with aggressive agents (see below). The honing should be done only about once in one or two months in the following way: you probably preferrably should have a large Belgian oil stone, completely smooth. Put some drops of oil (Buck's, or sewing machine oil, but no alimentary oil - no reason specified) on it. Cleaning the stone: Advises vary from cleaning with a cloth to cleaning with steel wool, or not cleaning at all. The ratio of cleaning is in removing metal particles out of the stone's pores, according to razor Edge Systems. Uncleaned stones kept their quality in their experiments, however. This still has to be cleared.
STROPPING, GENERAL When you shave, the cutting edge gets somewhat misaligned microscopically. It looks like microserrations, bending aside irregularly. If you put the knife away, the cutting edge stretches ('grows') spontaneously within 24 hours. After 3 or 4 shaves it should be aligned a little bit again and therefore you must strop. If you do that correctly, and treat the blade well, you only need to hone once every month or even year, and never send it in fro grinding. You need the right strop and the right paste. The game is, to postpone honing as long as possible, and to use the strop almost exclusively. Any other reports are due to wrong care. Stropping occurs at the exact same angle as with honing. Stropping serves to polish the edge and to align any remaining mislalignment of the microserrations. This implies that a hanging strop should be kept under tension to keep the angle correct. The former reports that the hanging-through would be beneficial for the edge, is incorrect, but may be this belief comes from experiences with plain blades (not hollow), as this will create a situation comparable with the primary/secondary angle/ relief story that applies to most knives. The hollow ground razor blade has only one single angle that should be conserved during all succesive procedures, ranging from grinding to stropping. Hanging thorugh will just round off the edge you carefully created before.
STROP TYPES Leather only Leather on one side and canvas on the other side: this is preferred above leather only because you first pre-sharpen on the canvas. Leather glued on wood and adjustable strops: for the un-experienced and for flat-ground blades. If you let a hanging strop hang through while stropping, you will blunt the knife. This may be a reason for the unexperienced to buy this latter type of strop. Juchten-leather: is more durable, and of better quality than Rind-leather. Pre-pasted strops, either with red, or with green paste. The strop should be reserved exclusively for the paste it has been treated with. Hanging strops with leather handles are more expensive but more comfortable than those with metal clamps.
PASTE TYPES White: chalk-containing paste for on the canvas-side of the strop ('Hanfseite') It is difficult to find it, it is in no catalog but it is available for ordering. Yellow: paste for on the leather side to make it sticky and souple, it is just fat. Red and Green: coarse and very coarse abrasives. They have never been designed for use with straight razors originally and should and need NOT be used. They will spoil the edge and are illogical, because any razor hone will be finer. When stropping is not enough effective, just hone. Black: a polishing paste almost without cutting effect, just as the white and yellow ones. You don't need this for sharpening results, but might want it to get a shine. However, the silicate in the leather strop will have an even better polishing effect, when used with the yellow inert paste, so black paste has no place here as well.
WHICH STROP WITH WHICH PASTE Probably the best combination is a hanging strop with a leather handle, Juchten-Leder on one side and canvas ('Hanf') on the opposite side, 450 mm long and 50 mm broad, with yellow paste on the leather side, and white paste on the canvas side. My personal experience with the leather-on-wood and adjustable strops is, that they don't give contact with the knife over their complete surface because it is somewaht convex, and that the hanging strops permit more control in that respect. Pasting the strop is only necessary two or three times a year with 3 cm of paste. You need only a few drops, and then spread with the palm of your hand. It makes the strop somewhat sticky ('Zug'), which is better for the alignment of the cutting edge. You will need a little tube for some years. Some manufacturers say that you can use either yellow or white both on leather and on canvas, but as the manuals differ from that opinion, I do not yet rely on that information, as chalk is more coarse than fat alone. I would advise not to use the white paste on the leather, only on the canvas.
STROPPING TECHNIQUE Strop only before shaving, after the edge could 'grow' for at least 24 hours, burt preferably 48 hours. If you strop the edge immediately after shaving, the misaligned microserrations behave as a burr, which will break off and penetrate the leather, which will turn into sandpaper. If you honed just before stropping, clean the blade with water and soap and dry with a cloth without touching the edge; this too is to prevent small metal parts to get stuck into the strop, which can damage the edge while stropping. Keep the tang between index finger and thumb and keep those fingers stretched. Place the blade flat on the strop. In case of a hanging strop, keep it under tension continuously, because if you let it hang through, you will create a round and therefore blunt cutting edge. Pull the blade over the strop away from the cutting edge and in the direction of the back. If you strop the other way in the direction of the edge (which is the case during honing), you will cut through the strop, or you will cause knicks which will damage the razor. In the course of this stroke, take care that the complete cutting edge has touched the strop. The pressure of the knife on the strop should not exceed the weight of the knife, to prevent rounding and thus blunting the cutting edge. At the end of the stroke, keep the blade in contact with the strop, and swing the blade 180 degrees, causing it to rotate around the back; the back should keep in contact with the strop. Then do a stroke in the other direction. Repeat this about 10-60 times. Do this procedure first on the canvas (about 10 times) next on the leather.
This communication reflects some personal conclusions of a private person; I have no commercial or private binding with any of the above mentioned firms.
-- Arthur Boon