Sharpness tests explained

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The Standard Sharpness Tests are sometimes described in the older barber texts, but the conventional or group wisdom, most of which is espoused here, sometimes varies from traditional sources.

Disclaimer: The shave test is the only test which will positively identify a shave ready razor. All other tests on this page are meant for testing the sharpness of a razor's edge during the honing process. These tests are neither a substitution nor a replacement for the shave test.

TST - The Shave Test[edit | edit source]

Sharpness tests explained 1.jpg

Performing The Test[edit | edit source]

Shave. Enough said.

Interpretations[edit | edit source]

  1. If you achieve a close comfortable shave with no pulling or scratching then your edge is in good trim.
  2. Pulling or getting caught up on the whiskers is a sign that the razor is not sharp enough.
  3. Skimming over the whiskers or a scratchy sensation, particularly one which leaves prolonged razor rash in appearance and/or sensation is a sign that the edge has been over honed, or more likely underhoned. With an over honed or rolled edge, the tip of the bevel has become too thin and folds back too easily. Most of the new honers tend to leave microchips on the edge, which will never give a good shave either.

Finer points[edit | edit source]

  1. TST is the only definitive test for a finished straight edge. No arguments.
  2. Stick to your regular routine. Don’t try any new preparation or experimental shaving techniques and you will know explicitly how well your razor shaves.
  3. With unsatisfactory edges one may feel a tendency to ‘muscle through’ the shave which should be resisted. Go back to the hone until you get the easy ‘hot knife through butter’ response indicative of a great shaving edge.

TPT - Thumb Pad Test[edit | edit source]

Performing The Test[edit | edit source]

Sharpness tests explained 2.jpg
  1. Hold the razor in your dominant hand and aim the edge upward.
  2. Place the fingers of your off hand along the downward facing spine for absolute control over how your thumb contacts the shaving edge.
  3. With a moistened thumb pad, draw your thumb very gingerly across, not along, the edge repeating all along its length to feel how it grips or bites into your thumb print.

Interpretations[edit | edit source]

  1. If the edge has a faint tickling sensation and just starts to grip onto your thumb pad then you are in the right neighbourhood for a shave test.
  2. If the edge bites and grips your thumb pad relentlessly wanting to cut in and not let go, then the edge may be over honed.
  3. If the edge tickles your thumb and feels like a very sharp knife with a good cutting edge then you are not sharp enough. This sensation is usually felt coming off a medium hone like a 4,000 grit water stone.

Finer points[edit | edit source]

  1. The cross edge action of the thumb is done much more carefully than one would normally do it for a knife since you are looking for different responding factors.
  2. I regularly perform this test after every few laps on the hone to chart the progress in the creation of the edge.
  3. The sensations described above are from my personal vantage point and your perceptions may vary. The definitions cannot substitute for the actual experience of sensation since perceptions depend primarily on the tactile sensitivity of the tester. Calloused hands, for example, may find it difficult to accurately grade a razor’s edge with this test.

Alternative TPT Method[edit | edit source]

The traditional thumb test to evaluate shave readiness is as follows:

Hold razor fully opened by the handle with point "pointing" towards the ceiling. Lightly place moistened thumb at heel of razor edge, first 2 fingers on spine, and lightly move the thumb, not the razor, move the thumb lightly along the edge towards the point. The thumb should "stick" or bind along the edge. This is because the razor is actually slightly cutting into the outter layer of your skin. When the skin binds, stop, lift thumb and replace higher up the edge and repeat until you cover the entire edge of the razor. If the thumb glides smoothly along the edge without a "sticky" feel, the edge is not cutting into the skin and is not yet sharp enough to shave.

I can't emphasize enough that this test is done with a light touch, or you may do more cutting than intended. The fingers on the spine help control pressure and movement of the thumb.

HHT - Hanging Hair Test[edit | edit source]

This sharpness test is highly controversial. Please refer to its main article: Hanging Hair Test, from trick to probing method to understand its pros and cons in full. Essentially, for some hairs a shave ready razor will not "pass" the test, and for some hairs a razor that won't shave well will "pass" the test.

Performing The Test[edit | edit source]

Sharpness tests explained 3.jpg
  1. Hold the razor in your dominant hand and aim the edge upward.
  2. Hold a clean hair, root end out in your off hand.
  3. Slowly bring the hair down on the upturned edge about 1-2 cm (½”-1″) out from where your finger grips the hair. Repeat all along the length of the edge.

Under no circumstances should you swipe the hair or razor in an action anything closely resembling a swift motion!

[1]

Interpretations[edit | edit source]

  1. If the hair falls away from the razor cleanly and effortlessly then your edge is in excellent shape for a shave test.
  2. If the hair catches or sounds as it clips then it is some minor fraction less than perfect, but may still provide a very comfortable shave. The razor may be overhoned and still pass the HHT in this manner in which case the razor will provide a less than comfortable shave.
  3. If the razor grabs the hair and tears it down its length rather than cutting it in half then it is unlikely that the edge is sharp enough to shave well.

Finer points[edit | edit source]

  1. These are interpretations of results from a razor off a fine hone. Razors will ‘pass’ more easily after having been stropped, but that defeats the purpose of the test somewhat. I strive for the most exacting of circumstances by testing after honing on an 8,000 grit Norton. With this methodology I have found that when I consistently get a good pass on the HHT, I get a great shave.
  2. There are variations, like moving the razor above your skin to see if it clips extended arm hairs and such and these are all fine, just remember that each change you make to the standard operations described above, changes the way the razor responds and may change the interpretation of those results.
  3. There is probably no other test that is as widely discussed on the forums as HHT and for good reason. There are so many variable factors in HHT, especially to the uninitiated, that it is sometimes impossible to use. The quality of the razor itself has some part to play, but the action of the tester is, I suspect, more unique. How far out do you make the cut? What angle do you hold the hair at? Do you draw the hair along the cutting edge at all or bring it straight down? All these factors and more come into play. Confounding the test even more is the fact that no two individual hairs are alike. Finer hairs will prove more challenging to pass than coarser ones. Clean, freshly washed hairs will also pass easier than a hair with a day or two worth of oil on it. I’m sure this list could go on. Attempts to standardise HHT so that conditions are the same or relatively the same for all testers are, in my humble opinion, futile. The effort needed would likely be time consuming and the determinations questionable at best. Instead, I trust in this. Barbers have been using HHT for centuries at least and have the combined wisdom and experience to lead us in the right directions. We do not need to reinvent the wheel. I’ve just told you how to make it round. The only thing left to do is perform HHT many times and begin to understand for yourself what it means when the razor responds in different ways. If you are not convinced a hair is up to the test, try a different one. If the right tools like clean, coarse hairs are your troops, then persistence is your greatest ally.

For a very detailed account of how HHT results may reveal characteristics of the razor's edge please read, Hanging Hair Test, from trick to probing method.

TNT - Thumb Nail Test[edit | edit source]

Performing The Test[edit | edit source]

Sharpness tests explained 4.jpg
  1. Hold the razor in your dominant hand with the edge facing downward.
  2. Extend your wet thumbnail, face up.
  3. Slowly and gently draw the edge along the top of your thumbnail.

Interpretations[edit | edit source]

  1. If the razor passes cleanly over your nail, cutting in slightly then the bevel is set.
  2. If the razor glides smoothly and effortlessly over your nail, the razor is dull (overhoned razor with a rounded edge is also dull).
  3. If the razor catches or bumps across your nail, then it has some micro chips that need to be honed out.

Finer points[edit | edit source]

  1. This test will damage the shaving edge so it should only be done on an edge that you intend to keep honing on the 4000 level hones. Its primary purpose is to determine whether the bevel is set properly.
  2. This test is sometimes seen as the least useful of the tests in this article as it is the most dangerous to the shaving edge and the results are also the most vague to interpret.

AHT - Arm Hair test (a work in progress)[edit | edit source]

This test, as any test really, is highly individual. Arm har is just as individual as our beards. The key to this test is to calibrate it so that one can interpret the results for it to be a meaningful tool in the honing process.

Performing The Test[edit | edit source]

  1. This test can be used throughout all stages of honing.
  2. The difference being at what height one attacks the strands of hair being shaved. For bevel setting purposes, start out with cutting hair at the base of the strand. For the final polish/finishing, try cutting the "tree-tops" of the strands.
  3. At all stages one should find a certain patch of hair that one will use every time, for the sake of consistency. Whatever place one decides to use (arm, thigh, leg or other), it is important to try to use the same general area as this will help in calibrating the results over time.
  4. It is common to go against the grain when performing this test, but whatever gives the desired result is fine. Lead the razor towards the hair at a similar angle as when performing the actual shave stroke.

Interpretations[edit | edit source]

  1. An already shave ready razor would provide a certain amount of evidence when used to test the AHT, but remember that each razor is unique and could provide different results than others.

Finer points[edit | edit source]

Conclusions[edit | edit source]

  1. It’s largely up to you. You will get better stimuli from different tests than the next guy and that’s fine. Do what works for you.
  2. Keep the discussion going. Even though people tend to describe the tests in their own way, sometimes talking about it can give you a new perspective or help you correct a minor error in performance.
  3. There are also some non-standard tests that get used such as dry arm shaving and the paper towel test and these should continue to be explored as well. For some guys they may supplement the standard sharpness tests, for others they may replace one. This too is a topic for discussion which should be encouraged so that more shavers may learn what others have discovered.


Acknowledgements[edit | edit source]

Originally posted by xman.[2]

References[edit | edit source]

  1. http://www.youtube.com/watch?v=ib5pO7qogpI
  2. http://straightrazorplace.com/old_site/inthedeepend/?p=113