How a razor blade can be damaged as it cuts human hair (2020)
<i>Item 1.</i> I hate sharpening knives and tools, so I wish someone would do a similar study for wood plane irons&#x2F;blades (including their different steel types) versus various grinding techniques, grinding grit sizes etc.; and also explain why good old carbon steel often gives a smoother cut than do many of the harder specialized steels that have Rockwell figures which are well into the 60s—even though the fact that carbon steel dulls and blunts much more quickly than do those much harder steels?<p><i>Item 2.</i> In a somewhat oblique vein, during COVID I always wore N95&#x2F;P2 masks in public and I always took extra heed to follow the instructions that came with them which read to the effect that <i>&#x27;this mask will be less effective on those with bearded faces&#x27;.</i><p>Clearly that stands to reason so the question is by how much.<p>I&#x27;m constantly bemused by the large percentage masks on bearded faces and whose wearers seem oblivious to the fact that their beards are likely rendering their masks ineffective. Especially so when I see doctors on TV who&#x27;ve beards and who are there specifically to proselytize the virtues of wearing masks. With their beards popping out from behind their ill-fitting masks, it seems strange to me that these highly trained medicos seem oblivious to the obvious fact that their beards are putting them at risk—not to mention that they are setting a bad example.<p>Now the issue is this: given that a clean-shaven, stubble-free face provides a better mask-to-skin seal than one with stubble, the questions are:<p>Does anyone know of whether tests have been done on N95-type masks to test the effectiveness of their mask-to-skin seals? If so, whether any significant leakage was detected at the seal and whether stubble growth throughout the day worsened said leakage (the implication being that by the afternoon&#x2F;evening masks would be less effective though increasing seal leakage)?<p>The corollary of the question would be to ask if a beard stubble impedes the effectiveness of the mask-to-skin seal then at what point in the growth of a newly-forming beard (at what stubble length, etc.) does the stubble render the mask ineffective (dangerous to wear)?