Posted by: Dr Jon Barnard | October 16, 2012

Under the microscope: razor blades

Have you ever wondered what the everyday stuff looks like close up?  If not, you need not read any further…

…but for the rest of you, let’s have a bit of fun.

Earlier this year, I had the chance to travel to Japan to see the lovely people of JEOL and see some of their kit. Wondering what to look at in the scanning electron microscope (SEM), I stumbled on a good sample suggestion whilst going through my morning ablutions that day:

Figure 1. Wilkinson Sword razor blades used by Yours Truly for that extra shave and shine. Image courtesy of the English Shaving Company (www.theenglishshavingcompany.com)

What do razor blades look like under the beam? What do they look like before and after a shave?
The razor blade before a shave

Figure 2. Fresh out of the packet, the Wilkinson Sword double-sided blade in the (scanning) electron microscope.

At low magnifications the blade looks, well, sharp. Figure 2 shows the cutting edge of the blade with a few bits of dirt attached to the surface (dark spots). The edge is nice and straight and the striations at the top of the picture suggest that these blades are either mechanically ground sharp (diamond-paste) or they receive a strong blast from an ion beam, which removes most stuff reliably.

The white bar at the bottom is a scale marker, i.e. it is essentially a little ruler which has the length indicated, in this case 10 um (micrometres). 1 micrometre is 1/1000 of a millimetre. To put things in perspective a human hair (I don’t have that many) is about 40 micrometres in diameter, i.e. if we had a hair in the microscope is would look like a cylinder about 4 of those white bars wide.

Figure 3. At higher magnifications the stuff on the edge becomes apparent (10 000 times magnification).

At a higher magnifications (, the blade starts to look a bit rough and the bits of dirt; grease from the waxed paper, dust from the air (that you breathe in!) are seen as the black blobs. Why black? Organic matter is mostly made up of carbon and hydrogen. When an electron beam strikes this stuff, they give off very few electrons (relative to the metal of the blade), so it tends to look dark.

The blade doesn’t look that sharp, despite the fact that it would slice though hair (and skin) really easily.

Figure 4. The cutting edge of blade close up (50 000 times magnification).

At 50 000 times magnification the blade looks really blunt and you can see that the edge has been slightly squashed. Given that these blades are metal, any handling of the blade during, e.g. packing them in their little wax-paper jackets, tends create a bit of stress at the blade edge that deforms them slightly. Even with the gentlest of handling (like when you’re carefully trying to mount this is your razor) gives rise to huge stresses at the edge in which the metal yields.

Notice that the scale bar is now 100 nanometres, i.e. 1/10 000 of a millimetre. Looking at this picture, the radius of curvature of the blade looks to be about 200 nm, i.e. about 1/20th the width of a human hair.

The razor blade after a shave

Figure 5. After scraping my head…the blade at low magnification (1000 times).

The blade was put through its paces in the shower. After a gruelling 15 minutes, the hair was gone and the blade had done its job- a nice shiny head to bring out to the Japanese sunshine.

At low magnification, the blade looks no different (figure 5). The blade is slightly darker from the oil and grease from my head and you can see that I’ve tried to clean it with a bit of tissue- the dark lines at an angle from the blade suggest organic material smeared along the blade edge.

Figure 6. Closer still (10 000 times magnifcation).

The gunk on the edge of the blade is now more apparent. A mixture of grease and residue is the blobby stuff and the blade edge is now littered with all sorts of stuff. There is a big blob of grease on the right hand side of figure 6.

Figure 7. Post-Jon, the Wilkinson Sword after scraping my head (50 000 times).

At the highest magnification the damage done to the blade is evident. The metal has suffered a huge amount of deformation (ductility) and the metal appears to have cracked in places. I have no idea what the white blobs are, but the fuzzy appearance towards the top of figure 7 suggests that, whatever it was it charges (accumulates electrons during the image) and blurs the image. The trauma of the blade seems to match that of my head- I managed to cut myself a couple of times during the shave. The things we do in the name of beauty!

Acknowledgement: JEOL for using their lovely JSM 7100TTFL and putting up with all my silly suggestions for samples to stick in it. Here is a picture of it:

Figure 8. The JEOL 7100FTTLS scanning electron microscope (without accompanying human).


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