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QUALITATIVE ANALYSIS OF THE EDGE CHARACTERISTICS OF
SHAVING RAZOR BLADES AS A FUNCTION OF CONTINUED USE
Sad_Scientist
Argon National Laboratory (USDOE);
Whisker Hall, University of Elements, USA
Keywords: Blade Sharpness, Shaving, Blade Degradation, Razor Quality
Abstract
This research focuses on depicting the degradation of a shaving razor blade throughout the
blade’s entire shaving cycle. Various SEM micrographs were taken from multiple angles of
seven razor blade edges, including an edge-on view, a side view, and a cross sectional view of
every single blade. Micrographs were taken after each of the first through fifth shaving cycles for
five different blades, along with a new razor blade and two control blades. For this research, the
razor blades were Feather Hi-Stainless Platinum Double Edge. Qualitative analysis results and
discussion are included in this paper.
Introduction
The sharpness and edge characteristics of cutting utensils and their affects on various materials
have been the focus of many studies, anywhere from slicing watermelons to slashing human
flesh1,2,3,4,5,6,7
. However, the scientific research has not yet pierced the shaving community. Post-
pubescent males and females who are familiar with the wet shaving technique have no doubt
noticed that the periodicity of nicks, cuts and irritation increase as the used blade life increases8,9
.
This is also generally accompanied by a decrease in shave quality. There are many potential
causes for such poor performance of the razor blades over continued use, including but not
limited to corrosion10,11
, plastic deformation12,13,14,15
, bending flow16
, chip formation17
, and burr
formation16,18
. These defects in the razor blade can result from many parameters, possibly
including but not limited to whisker thickness, shaving cream lubricant, mineral content of the
water, number of consecutive shaves, shaving technique, and storage humidity.
Before reading the rest of the paper, it would be best to get caught up on terminology used in the
shaving community, as well as basic processing steps and their consequences in the world of
razor blade manufacturing. Figure 1 shows a schematic cross sectional view of razor blade edges.
The dashed line shows what a perfect, ideal tip of a razor blade would look like after sharpening.
In real life, “debris deposit” occurs during the grinding and polishing process which gives rise to
the solid black line. During the polishing step, tiny abrasive particles move along the surface,
either towards or away from the edge tip, pushing scraped up metal and debris in front of and
behind the abrasive particles. This is responsible for the rounding of razor blade tips that are
fresh from the manufacturer. Figure 2 shows another schematic which points out the direction of
the polishing media, as well as parts of the blade that will be referred to throughout the rest of the
paper.
Figure 1 - Cross section view of razor blades, showing the debris deposit at the top of the picture which is responsible for
the curved, solid line. An ideal edge is shown as the dashed line for comparison. Image from J. Verhoeven16.
Figure 2 - Schematic showing parts of a blade and polishing abrasive direction. The ride line shows a possible direction of
abrasive particles during the sharpening step, the other direction being downward.
In this experiment the author attempts to control or possibly even avoid many of the parameters
that are considered to affect the edge quality of razor blades and focus on only one variable, the
number of consecutive shaves before switching to a new razor blade. The idea is to qualitatively
educate the shaving community in the mechanical behavior of a typical razor blade as it is used
over time.
Bevel face
Tip
Experimental
For this study, an experienced shaver (experimenter) consistently took a hot shower before each
nightly shave at approximately the same time of evening after the same amount of sleep the night
before. Exfoliation was performed with Clean & Clear Oil Free facial cleanser on a typical wash
cloth with firm pressure. This ensured both consistent whisker growth and a properly soaked
beard. After the hot shower, the experimenter dried off the body without drying off the face to
allow the moisture to continue to soak the beard. Hot water then filled the sink and the badger fur
brush (DOVO Satin Silvertip Shave Brush), along with the glycol based shaving soap and soap
dish, were allowed to soak and come up to temperature. A hot wash cloth at approximately the
same temperature was simultaneously pressed against the experimenter’s face while the brush
and soap were soaking. After approximately 3 minutes of soaking time, the experimenter
produced a rich lather using the brush and soap. Care was taken to produce a consistent viscosity
of lather throughout the experiment, but no rheological measurements were performed to prove
such consistency.
The lather was then applied to the experimenter’s face, first in a “circular” motion to fluff up and
massage all sides of the whiskers with shaving soap, then in a “sweeping” motion to even out the
thickness of the lather19
. Lather time is approximately 90 seconds total. Once fully lathered, the
razor (Merkur "Barber Pole" Hefty Long Handled Classic) and razor blade (Feather Hi-Stainless
Platinum Double Edge) were dipped in the hot water to bring up to a comfortable shaving
temperature. Two complete passes of shaving were carried out, with a quick soak and full lather
of the face in between passes. For each pass, care was taken not to overlap the razor blade with a
previously shaved path that was missing lather. Both passes were swiped in the same direction as
the grain of the beard. Since each razor blade was double edged, either of the two edges were
alternated for each swipe ensuring a consistent wear on each edge.
After the first nightly shave, the razor blade was returned to its original wax paper wrapper and
then stored in a makeshift desiccator made from a Pyrex® container with anhydrous calcium
sulphate to prevent further oxidation, corrosion, or damage to the blade’s edge. Razor blade #2
was used the following night with the same procedures, only this razor was used for 2
consecutive shaves (4 passes, total). Razor blade #3 was used for 3 consecutive shaves, and so
on, until 5 razor blades were used. For all blades that were used for more than one night, the
razor was forcefully tapped dry at the end of each shave. In between each nightly shave, the
Feather razor blades were stored while attached to the Merkur razor as this is common practice in
the shaving community20
. The storage area was well ventilated at approximately 40% relative
humidity. After each blade cycle was completed, the blades were dried with pressurized air
before being placed in the desiccator. For control blades, a brand new razor blade was rinsed
with tap water and left to air dry for 5 days, and another razor was used once for shaving and left
to air dry for 5 days. This allowed us to account for any corrosion that took place throughout the
experiment.
At the end of the shaving stage of the experiment, all of the razors were simultaneously taken out
of the desiccator and prepared for analysis. The razor blades were sectioned so they could be
viewed from an edge-on direction (i.e. the tip of the blade is at a right angle to the line of sight of
the image), a side profile, and a cross sectional view. Gold sputtering was needed for the cross
sectional view. Micrographs were obtained with a JEOL 59101LV scanning electron microscope
(SEM) with energy dispersive x-ray spectroscopy (EDS) capabilities for elemental analysis.
Results and Discussion
SEM micrographs using secondary electron imaging mode can be seen in Figure 3, where the
razor blades were imaged edge-on. Some of the razor blades were unfortunately tilted away from
perpendicular to the beam making it difficult to discern the very tip of the blade, therefore
guidelines were inserted in the picture to clarify where the tips reside. The micrographs clearly
show a pattern of increased wear as the number of consecutive shaves increase. Starting with the
brand new razor blade in figures 1 and 2, a clean tip can be viewed from top to bottom of both
micrographs. This was typical throughout the entire razor blade. Small ridges and imperfections
on each face of the bevel appear to be 1-3 μm in size towards the very tip, but texture from
sharpening can be seen behind that portion. This region towards the tip is due to debris deposit,
or plastic deformation towards the very tip of the razor blade that occurred during the sharpening
process.
Now continuing with the edge of razor blade #1, it can be seen that this supposed bending flow
region is no longer present. Instead, this immediate region appears to have smoothed out, with no
visible deformation to the very tip of the razor where the two faces meet. This was typical
throughout the entire length of this sample’s tip. The blemishes and imperfections that can be
seen on #1 were completely on one face or the other, never overlapping the very edge. These
blemishes are approximately 5 μm in size, and were typically seen in intervals of a few hundred
microns apart. The edge appears quite sharp as there is neither blunting nor deformation that is
visible at this magnification. It appears as if the debris deposit portion of the blade was rubbed
away during the first shave.
With razor blade #2 we start to see significant deterioration of the blade. There are many more
visible blemishes along each face of the bevel. One thing to note is the blemishes tend to be
textured in a direction parallel with the blade edge. That is to say, each of the blemishes tends to
be longer along the vertical axis of the image. This is due to the textured microstructure that was
present in the razor blade due to the rolling process during manufacturing. A thin strip of metal
with the basic internal composition of the final product is made with a cold rolling process,
which turns the equiaxed grains into elongated, textured grains. These textured grains remain
throughout the rest of the processing until the final polishing step. During the shaving process, it
is likely that a whole grain is dislodged from the surrounding microstructure, which would create
imperfections of the same shape we see in our micrographs. The very edge of the razor, where
the two faces of each bevel meet, appears to be somewhat damaged as well. The grinding texture
on either face of the bevel from the sharpening process is much more pronounced in this
micrograph, but this is only due to increasing the contrast in the photo software.
Razor blade #3 has a more deformed tip running along the entire edge of the sample. Dark
blemishes that run along the tip of the razor are becoming visible, occurring at a greater
frequency than the previous two razors. The blemishes also appear to be slightly larger than the
previous razors, on average.
Razor blade #4 shows very long, continuous blemishes running along the entire edge of the
blade. These blemishes were typically 100 microns in length, and about 5 to 10 microns in
perceived width, expanding much further into each face of the bevel.
Razor blade #5 shows more tip deformation than any other razor. Large gouges can be seen at
the edge of the blade. These are further pointed out in Figure 4, with a side profile of razor blade
#5. For convenience, Figure 5 shows the side by side comparison of razor blade #5 with a brand
new razor blade.
Figure 3 - Edge-on view of razor blade tips. Red guidelines that highlight the tip for razors #3 and #5 are in red.
Figure 4 - Side profile view of razor blade #5. Notice the two 20 μm gouges on the edge of the blade, along with the 150 μm
crack running down the bevel face. These types of defects are partially responsible for nicks and cuts.
Figure 5 - Comparison of a brand new blade on the left, to blade #5 on the right. The texture from the polishing abrasives
can be seen clearly on the new razor blade, whereas blade #5 seems to have been smoothed out.
Figures 6 and 7 show cross sectional views of a new razor blade and razor blade #5, respectively.
This shows the increase in razor tip radius as a function of continued use. It can be seen that a
fresh razor blade has a tip radius of approximately 0.25 μm, whereas razor #5 has a tip radius of
approximately 0.5 μm. There is a larger error in the tip radius for razor blade #5 due to the
unknown foreign matter on the vary tip of the blade.
Figure 6 - Cross sectional view of a brand new razor blade. The tip radius was measured to be approximately 0.25 μm.
Figure 7 - Cross sectional view of razor blade #5. The tip radius was measured to be approximately 0.5 μm. Foreign
debris on the tip that was likely introduced in sample preparation makes it difficult to measure.
EDS measurements were performed on the brand new blade, as well as blade #5. Both blades
showed approximately the same amount of Cr which is to be expected, around 14 at%. The only
other alloying metal detected was Mn, at approximately 2 at% in each blade. However, only the
brand new blade showed any traces of Pt. This leads the author to believe that the Pt has been
sputtered onto the razor at the end of processing, only to provide a minimal cover of the blade to
prevent corrosion during the razor blade shelf life, as well as marketing reasons. This thin layer
of Pt would be easily removed during a single shaving pass, as the layer is likely nanometers in
thickness.
The control blades were was also examined with SEM for this experiment. There was no
discernable difference between the control blade that was only rinsed with water, and a brand
new razor blade. The control blade that was used once for shaving, then left out in the normal
environment (as opposed to a desiccator) appeared to be in the same condition as razor blade #1,
indicating that corrosion did not play a significant role in the edge characteristics of a razor blade
with continued use with these stainless steel blades. Micrographs for these control blades, as well
as other micrographs both included and not included in this document, can all be viewed online
in high resolution.
Conclusion
It has been qualitatively shown that the edge characteristics of stainless steel razor blades edges
deteriorate over continued use. This deterioration is a function of the number of shaves, not a
function of corrosion due to humidity. Grains on the faces of either side of the bevel are shown
to pull out with continued use, leaving behind a textured surface that might be responsible for
nicks and cuts. Portions of the very tip are also fractured off as seen from the side profile view
which may also lead to nicks and cuts. The edge tip radius of the razor blade has also been
shown to increase with continued use, which will hinder the ability of the razor blade to shear
through whiskers given the greater surface area. The razor blades were likely sputtered with a
very thin layer of Pt only for protection of the blade during the shelf life, or possibly marketing.
It should be stated that this experiment has a very small sample size of razor blades, and all of
the shaving was performed by one individual. Any inconsistencies with the experimenter would
lead to inaccurate results. More testing shaves would be needed with various razor blades,
performed by various people, in order to get better quantitative results.
Acknowledgments
I would like to thank mantic59 and the Sharpologist.com shaving community for their input
regarding this experiment.
References
1. S Leonov, et al., “Forensic Medical Characteristics of Stab Wounds Caused by Objects
Differing in the Blade Sharpness,” Sudebno-meditsinskaia Ekspertiza, 54 (2011) 16-18.
2. M. Raymond, et al., “The Effect of Blade Finish and Blade Edge Angle on Forces Used in
Meat Cutting Operations,” Applied Ergonomics, 36, (2005) 71-77.
3. S. Portela, et al., “Cutting Blade Sharpness Affects Appearance and Other Quality Attributes
of Fresh-cut Cantaloupe melon,” Journal of Food Science, 66 (2001), 1265-1270.
4. M. Raymond, et al., “Cutting Moments and Grip Forces in Meat Cutting Operations and the
Effect of Knife Sharpness,” Applied Ergonomics, 34, (2003) 365-382.
5. R. Meehan, et al., “The Role of Blade Sharpness in Cutting Instabilities of Polyethylene
Terephthalate,” Journal of Materials Science Letters., 18 (1999), 93-95.
6. A. Gent, et al., “Abrasion of Rubber by a Blade Abrader: Effect of Blade Sharpness and Test
Temperature for Selected Compounds,” Rubber Chemistry and Technology, 69 (1996), 819-833.
7. C. Arcona, et al., “The Role of Knife Sharpness in the Slitting of Plastic Films,” Journal of
Materials Science, 31 (1996) 1327-1334.
8. D. Moore, et al., “Mediating Shaving Irritation,” Cosmetics & Toiletries, 121 (2006), 49-52.
9. D. Ramsay, “Final Finish Aftershave,” U.S. Patent Application Publication, (2008).
10. A. Lebedeva, et al., “Effect of Pitting Corrosion on the Fatigue Strength of Blade Materials,”
Teploenergetika, 2, (1992), 11-14.
11. T. Shinohara, “Simulation of Solution Chemistry in Edge Corrosion,” ECS Transactions, 25,
(2005), 81-93.
12. N. Meckel, “Scalpel Surgical Blade Having High Sharpness and Toughness,” Patent
Cooperation Treaty International Application, (2001).
13. S. Sakon, et al., “Improvement in Wear Characteristics of Electrical Hair Clipper Blade
Using High Hardness Material,” Nippon Kinzoku Gakkaishi, 712 (2008) 604-609.
14. P. Alam, M. Toivakka, “Deflection and Plasticity of Soft-Tip Beveled Blades in Paper
Coating Operations,” Materials and Design, 30 (2009) 871-877.
15. M. Giri, et al., “Blade Coating of a Rough, Deformable Substrate,” Advanced Coating
Fundamentals Symposium, (2001), 236-246.
16. J. Verhoeven, et al., “Experiments on Knife Sharpening,” (Iowa State University, 2004).
17. N Sawada, “Dicing Device and Method,” Kokai Tokkyo Koho, (2001).
18. T. Gietzelt, et al., “Finishing of a Vapor Deposition Mask Through Micro-Drilling and Use
of Electropolishing for Burr Removal,” Jarhbuch Oberflaechentechnik, 66 (2010) 338-347.
19. Mantic 59, “The Ten Minute Traditional Wet Shave,” 2009. Sharpologist. 12 Oct. 2011.
<http://www.youtube.com/user/mantic59#p/u/34/-qSIP6uQ3EI>
20. Mantic59, “A Shaving Experiment,” <http://sharpologist.com/2011/10/a-shaving-
experiment.html>, (2011).
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