One of the most common questions which comes up in my conversations is: how do I know whether the razor is sharp enough? Given that most people have never had anything really, really, really sharp in their hands, it’s a good question! I consider straight razor honing to be at the extreme end of sharpening activities. There are few tools which need to be as sharp as a razor.
The question is made more difficult to comprehend because the vendors of razors tend to say that their razors are “shave ready, right out of the box”. Given the number of razors I hone which are sold to people by other vendors, I’d say that “shave ready” is a subjective term (at best!) which, in reality, means little to the end user. When a razor comes from a factory, it has what is called a “factory edge” and this is also true for knives of all types when purchased commercially. A factory edge is a rough approximation of what a shave ready edge should be.
The next question to come up is: how do we test a razor to see if it’s sharp enough for shaving?
Razor tests are all referential tests. They are subjective and not objective. They attempt to predict face shaving based on some test other than face shaving. Classic tests are the Hanging Hair Test (HHT) and the Thumbnail Test. The problem with referential tests is the answer to the question will vary from person to person conducting the test. Hair has a lot of variables to it such as presence of bumps along the hair which is what makes hair curly or not (the bumps absorb water differentially and that’s what makes the hair curve). Hair thickness varies from coarse black hair to thin red or blonde hair. The surface of the hair varies as some hair is smooth and some is anything but smooth! Therefor, when someone does an HHT and tells you the razor is sharp, it may not perform well on your hair. It’s the same with the Thumbnail Test. Nails vary as to thickness, brittleness, and smoothness.
The only way to know if your razor is sharp enough for shaving is to shave your face with it. It may fail an HHT but shave wonderfully. It may cut thumbnails really well but pull and skip on your face. I’ve seen blades do the above enough not to even bother with the HHT or thumbnail test anymore except for entertainment purposes.
The tests I use to see if a razor is sharp enough to send back to a customer are 1) visual inspection with a microscope on both sides of the razor and from heel to toe and 2) I shave a small portion of the back of my hand or arm. Visually, I can tell if a razor is sharp by the color of the bevel under magnification. If it’s uniformly sharp, the reflective qualities will be uniform. If there are any red or gold colored areas, those are tiny pits which are refracting the light differently than the surrounding metal. Next, I’ll shave my arm usually with nothing more than some cold swarf water from the Shapton pond. If I get a smooth, hairless patch, it’s ready to ship.
I know there are sources on the web which poo poo the shaving of the arm test. I disagree with them. As ALL of the tests are referential, they all attempt to predict face shaving from some other reference such as the HHT or thumb nail. All of the tests succeed or fail at prediction to one extent or another since none duplicate exactly the hair on your face. The visual examination I use and the arm shaving work for my customers and I hone A LOT of razors every week and have done so for almost 10 years.
The Perfect Edge method for honing razors is a progression of stones which go from the 1k to 4k to 8k to 16k to 30k. I use the Shapton system which includes the extraordinarily flat glass stones held in a Shapton stone holder mounted in the Shapton pond which sits on a granite surface plate on an isolation table purchased from a factory quality control laboratory. Everything is flat and level and there is no vibration or skipping of any component. The hones are flattened daily with the Diamond Glass Lapping Plate. A razor which is honed out to 30,000 grit pretty much wipes the hair off without any sound.
And that’s how you achieve . . . The Perfect Edge.