When I first became seriously interested in this topic about four years ago, consistently honing a straight razor to the level of keenness required for a close, comfortable shave challenged me. Having earned my living for the past 25 years solving problems like these, I began by searching for relevant scientific literature as well as reading the opinion-based resources of internet forums. I was surprised to find almost no published scientific work, although likely there is a wealth of information in unpublished reports in the research libraries at the Gillette and Schick corporations. The internet forums proved to be a dead-end, although for different reasons. Over the past 4 years, I have learned a great deal about sharpening, honing and stropping and have shared some of that knowledge here.
When I started this blog, just over two years ago, I chose to concentrate on demonstrating what happens at the apex of a blade, particularly since the relevant length scales are much smaller most people can comprehend (or see with even the best optical microscope). When writing these articles, I have made a concerted effort to avoid drawing conclusions, instead just showing what actually happens at the sub-micron scale during the various sharpening processes. I have chosen not to use this a forum to explain how to sharpen, but rather to provide a resource for people with sufficient interest and comprehension to improve their own understanding. In this article, I will break with the trend and share a simple and reliable technique for honing a straight razor.
It is usually claimed that honing a straight razor is more difficult than sharpening a knife or other bladed tool. While it is certainly true that some people make it more complicated, it is not necessary to do so. It is also commonly asserted that honing a straight razor requires a set of fine and expensive hones – this is also not true. I demonstrate here that only two hones are required, one coarse hone for expeditiously setting the bevel and one fine hone for polishing away the apex damage created by the coarse hone. The second hone does not need to be any finer than 4k grit. It is also important to understand that scratches in the bevel are of no consequence when the bevel is micro-convex as the scratches do not reach the apex.
I have personally used the approach described below for approximately two years, and have shave-tested well over 100 razors prepared by this approach. I have recommended this technique to people having difficulty honing their own straight razor and have not yet had anyone tell me they were unsuccessful. To be clear, there are many other ways to accomplish this result; however, this is the simplest and most consistent approach that I have found.
This approach is quick and easy if you are honing a straight razor that has been shave-ready (not a restoration or a factory edge, for example) and not been damaged (no chips that you can feel with your thumbnail) and is not warped. A smiling blade is not a problem, provided you use a rolling stroke to shift pressure along the length of the blade.
If you are unsure of the condition of the blade, raising a burr that you can feel using a 1k stone, as you would when sharpening a knife, is a helpful diagnostic. However, I would only do this once, as it is a waste of steel. It is important to remove this large burr with edge-leading strokes as the steel near the base off the burr will be damaged from the burr flipping side to side.
The goal of the first step is to remove enough steel from the bevel faces to ensure that they meet and form an apex (usually called “setting the bevel”). Up to this point, the approach for sharpening a knife and a straight razor is essentially the same. Although with a straight razor we want to avoid introducing chips in the edge, something we are less concerned about when sharpening a knife. A straight razor has a narrow bevel angle (commonly 16-17 degrees, inclusive) and is more susceptible to micro-chipping than blades with included angles of 25 degrees or more.
My preference is to set the bevel with high quality 1k stone such as a Naniwa or Shapton to achieve a good trade-off between abrasion rate and the size of the micro-chips in the apex. Lower quality stones will also work if edge-leading strokes are avoided. As a rule of thumb, using the 1k stone long enough to make black swarf, then ending with about 20 edge trailing strokes is sufficient. The reason for the edge trailing strokes is explained in the series of images that follow.
To show how robust this technique is, for this demonstration I use two of the worst choices for hones that I own, the DMT extra fine (1200) and the 6k side of a King 1k/6k combination stone. The DMT is problematic because it produces micro-convexity and substantial damage and distortion to the apex. The King 6k, although a good polisher, causes significant micro-chipping to the apex when used edge leading.
The first step, here shown with the DMT extra fine (1200) diamond plate, produces a near-triangular bevel but with damaged and distorted steel at the apex. This is all that is required at this step – it is of no consequence whether the blade can “shave” at this point.
The second step is to polish the bevel and remove the damaged steel near the apex with a 4k to 8k level hone with about 20 edge-trailing strokes. There is no need for a feather light touch, but the edge trailing strokes should not flex the blade either. The goal is to produce a foil edge – more steel than we want at the apex. After this step, the blade is in similar condition as it would be when using the Murray Carter 1k/6k method prior to folding the burr by cutting into a piece of wood. In the example here, the blade received 20 edge-trailing laps on the King 6k to produce a micron-sized foil burr.
In the low magnification cross-section view (below) a micron-sized foil-burr is observed at the apex beyond an otherwise triangular bevel. The goal of this step is to have the apex “longer” than we require so that there will be no damaged or chipped regions remaining after the strop-based burr-removal step. Again, it is of no consequence whether the blade can “shave” at this point.
The third step is to remove the burr using the hanging denim strop with metal polish. This burr-removal technique was detailed in Burr Removal – part 1. I normally use a strip about 4cm wide and 25cm long, but you can make it larger if you prefer. As a rule, I do 30 laps. Again, there is no need for feather light strokes – on a weigh scale I would expect to see between 100g and 150g. I tape the denim strip to the edge of the bench with duct tape, and do not pull nearly hard enough to pull it loose. This will micro-convex the blade, removing all traces of the foil-burr. I replace the denim strop when it becomes dark and glazed, after ten to twenty uses. I have analyzed and tested a variety of metal polishes and all performed similarly.
The purpose of this third step is to micro-convex the apex and remove the foil-burr in preparation for the diamond on leather strop which will then shape the apex for shaving level keenness. As I have shown previously, diamond on leather will convex the apex but not remove the burr which forms as a consequence. A typical example of a foil burr that results when transitioning directly from a hone to a diamond on leather strop is shown in the two images below.
The denim stropping step not only removes the burr formed by edge-trailing strokes on the hones, but the “pre-existing” micro-convexity that it imparts will prevent the formation of the foil-burr that typically forms when stropping on diamond-loaded leather (shown above). The foil-burr (above) results from incomplete (micro) convexing of the apex. The result of the loaded denim stropping step is shown below.
With the denim strop, there is some care required to ensure that suitable downward pressure is used. With too little force, the apex will not be sufficiently convex to avoid the formation of a foil-burr with the diamond on leather strop. I typically use the same force on all strops, both loaded and clean.
With too much force, the apex will convex too much and not contact the surface of the diamond on leather strop. Too much pressure will also turn the strop black more quickly as the entire bevel is convexed (and more metal is removed).
Typically, the blade will shave reasonably at this point in the procedure, although it is not likely to tree-top fine arm hair or pass the hanging hair test with any great success without additional stropping on clean or loaded leather.
The fourth step is to clean up the apex and maximize keenness after the denim. This is easily accomplished by stropping on smooth leather loaded with diamond spray . Again, as a rule, I do 30 laps. In this example, a hanging kangaroo leather strop loaded with 0.25 micron poly-diamond spray was used. I typically use a latigo leather strop for this step – there is no need for exotic leathers.
Depending on the pressure applied during the stropping steps, a very small (but inconsequential) burr may remain on some parts of the blade. The foil-burr shown below is not typical, but even in the event one of this magnitude is formed it is not a problem.
This inconsequential burr can easily be removed by stropping on clean denim. Any clean linen strop component will suffice.
Finally, prior to shaving, I strop on clean leather, 30-50 laps. This will deposit a thin layer of organic “lubricant” on the surface of the blade, as well as ensure that the apex is aligned. At this point, the blade should easily “tree-top” the finest arm hair and score HHT-5 on the hanging hair test.