Observations on the Cutting of Beard Hair, J. Society of Cosmetic Chemists, 1976

[SiBurning]

Full pdf is online: Observations on the Cutting of Beard Hair

Synopsis

A device is described which permits measurement of the force required to CUT a BEARD HAIR FIBER under a variety of conditions. Studies with this device show that the force required to cut wet beard fibers with commercial razor blades is about 65 per cent less than that of dry fibers. Beard hair is almost completely hydrated by exposure to water for about 2 minutes at room teanperature, and this hydration is accelerated by an increase in temperature. The force required to cut a beard hair increases with increasing fiber cross-sectional area, but this correlation is not perfect. The force required to cut beard hair is not lowered below that in water by the presence of a wetting agent, a shaving cream, or a soap solution. The force required to cut wet beard hair with a razor blade is lowered significantly by very severe attack on the fiber. On the other hand, the force required to cut beard hair increases as the rate of blade travel increases.

 

[Vlad]

So this means, according to the study, lather is only useful in so long as it keeps water on the beard?

 

[SiBurning]

These scientific papers often say a lot less than we'd like to know...

There's later research that does a better job.
Cutting Characteristics Of Beard Hair; S. M. Thozhur, A. D. Crocombe, P. A. Smith, K. Cowley, M. Mullier; 2005-2007
I reviewed it a bit here.

Basically... The force to cut is mostly about water, but there is a slight benefit from increasing temperature and pH, and possibly from surfactants and emollients.

But don't forget the other side of the equation--lubricating and protecting your skin from the blade.

I also posted another article Insights into shaving and its impact on skin that talks about how... I'm reading into it quite a lot, but... how a brush might help prevent ingrowns and maybe even make for a closer shave by untrapping hairs from skin, which at a very small level is almost like a stiff gel.

Sure, we already know more than they do, but it's nice to know why Kyle's Prep works so well.

 

[Haiku]

Also, if I'm reading right, it seems that the faster one cuts the more force is needed, so the advice is go slow.

 

[kingfisher]

Full pdf is online: Observations on the Cutting of Beard Hair

Synopsis

...... The force required to cut wet beard hair with a razor blade is lowered significantly by very severe attack on the fiber. On the other hand, the force required to cut beard hair increases as the rate of blade travel increases.

These two sentences appear to contradict one another. In the first, it sounds like you need LESS force when your razor is moving faster, and in the second, the opposite. I don't get it.

 

[SiBurning]

Chemical attack. See the conclusions.

 

[Haiku]

Having now read the study, it seems to me that these two guys must have had a ball doing this study. Just picture being able to do this kind of stuff for a living.

 

[ShavinBacon]

Interesting....it basically debunks (or a better term would be that it takes a lot longer to work) cold water shaving. It says it takes 2 minutes for room temperature water to properly hydrate beard hair but that time shortens with an increase in temperature. Ergo, cold water would take longer than 2 minutes....

 

[Haiku]

Interesting....it basically debunks (or a better term would be that it takes a lot longer to work) cold water shaving. It says it takes 2 minutes for room temperature water to properly hydrate beard hair but that time shortens with an increase in temperature. Ergo, cold water would take longer than 2 minutes....

2 minutes at room temperature, 73.4 degrees F, 23 degrees C, plus or minus 1.5 degrees or: 70.7 to 76.1 degees F. The lower end is in fact pretty cool. It seems they did not test cold water. No, I don't think ergo works here.

Shorter time if water is 30 degrees C. That means 86 Fahrenheit. The amount of time for hot water would be insignificant in any even given that we're only talking about 2 minutes.

From what I can see, "cold" water as often discussed on this board really means "cool" which I suspsect really means exactly what was tested ie. "room temperature".

Also cool/cold water also means reduction in inflamation resulting in less razor burn.

If anything, the study debunks using water any hotter than room temperature, in that 86 Fahrenheit does speed up hydration, but only insignificantly in the scheme of things. It seems clear that 86 Fahrenheit is pretty much a waste given that it only takes 2 minutes to hydrate a beard at 70.7.

 

[ShavinBacon]

Do you mean to tell me that when I have tried cold water shaving using a bucket of ice water that that isn't what everyone else is doing?

HA!

 

[Haiku]

Do you mean to tell me that when I have tried cold water shaving using a bucket of ice water that that isn't what everyone else is doing?

HA!

The image of a guy with a bucket of ice water for shaving made my day, thanks!

 

[SiBurning]

Note the anomaly around 30C (86F) in Figure 8. Or is the real anomaly at the curve at 24C? If you really want to see what's happening, compare the 24C curve against figure 6.

 

[mblakele]

Also, if I'm reading right, it seems that the faster one cuts the more force is needed, so the advice is go slow.

The thing is... we have human limits. I do not think I could shave at 0.5-in/min, and if I tried I think my angle would suffer. http://badgerandblade.com/vb/showth...m-Hand-Speed-for-Two-Blade-Razor-Shaving-quot talks about another paper, which I cannot seem to retrieve it right now, but I gather that it recommends a minimum of 85-in/min with a double-blade system and says that faster is even better. Maybe the relationship is different above 50-in/min?

But I have another reason to question the conclusions in this paper. These researchers had their own limits to contend with, which caused them to use this unrealistically slow cutting rate.

It is noted that a rate of cutting of 50 in./min approaches normal shaving conditions. Nevertheless, the much slower rate of 0.5 in./min was routinely used here in order to avoid the time-consuming complication of employing a storage oscilloscope.

So they measured 50 as a test, and a few rates around 3-20, but most of the testing was at an inhumanly slow cutting rate. Does this also mean that they measured FTC in completely different ways at the high end and the low end of cutting rates? Ah yes, earlier they explain the methodology:

The TM Instron Tester recording system was used for measuring the cutting forces at speeds up to 5 in./min. A Tectronix©* storage oscilloscope (Model RM564) fitted with a strain bridge was used to measure forces at cutting speeds up to 50 in./min. By combining both methods, cutting forces were measured at speeds ranging from 0.1 in./min to 50 in./min

Hmm.... This sounds like using two different thermometers, one to measure freezing and the other to measure boiling. If they have not been calibrated across some common range of temperatures in the middle, how can we compare their results? Was there any attempt to calibrate these two techniques over some common range of cutting rates?

Up at 50-in/min, where they say "approaches" where we shave ourselves, there only seems to be some random-looking variation around the same cutting rate. FTC varies by about 1-g in either direction for the same hair sample. Down below 3-in/min, where they definitely used the TM Instron Tester, sample "x" shows no correlation between cutting rate and FTC. Sample "o" seems to show some correlation, but there is not enough data to say.

So I am not convinced that they proved anything about the relationship of cutting rate to FTC. For me, this casts doubt on the relevance of any of their FTC measurements to actual shaving. Possibly they only showed what would work best for a robotic barber based on the TM Instron Tester.

That is too bad, because I think this work has widely cited. Figure 6 looks to be the (uncredited) source for this graphic, published by Gillette:

 

[SiBurning]

So I am not convinced that they proved anything about the relationship of cutting rate to FTC. For me, this casts doubt on the relevance of any of their FTC measurements to actual shaving.

Do you mean all of the other numbers should be higher for normal shaving, or that the measurements themselves are untrustworthy? Or perhaps something else?

 

[mblakele]

I think they should have either used more realistic cutting speeds, or done more to show that measurements taken at 0.5 in/min would be relevant to shaving with much higher speeds in the real world. Two orders of magnitude is a wide gulf to bridge.

 

[SiBurning]

Two orders of magnitude difference in speed and only two or three times the force. Seems like a small difference to worry about.

 

[Whilliam]

If anything, the study debunks using water any hotter than room temperature, in that 86 Fahrenheit does speed up hydration, but only insignificantly in the scheme of things. It seems clear that 86 Fahrenheit is pretty much a waste given that it only takes 2 minutes to hydrate a beard at 70.7.

Yeah . . . but hot lather feels soooooo good.

 

[alex2363]

I think they should have either used more realistic cutting speeds, or done more to show that measurements taken at 0.5 in/min would be relevant to shaving with much higher speeds in the real world. Two orders of magnitude is a wide gulf to bridge.

Two orders of magnitude difference in speed and only two or three times the force. Seems like a small difference to worry about.

I was just wondering, even though it is a great link by Steve, wouldn't these findings from 1975 be out dated compared to today's more technological advancements in research. I mean, Gillette spends more than $750 million for the Mach 3 research and even more on Fusion . And I am sure that a bulk of that research entails more advanced insight into the shave technique and results.

 

[SiBurning]

Here's the latest & greatest. The big difference is they're learning how to get data on live subjects actually shaving.

The document referenced here is a building block, necessary to understand what comes later.

 

[mblakele]

I was just wondering, even though it is a great link by Steve, wouldn't these findings from 1975 be out dated compared to today's more technological advancements in research. I mean, Gillette spends more than $750 million for the Mach 3 research and even more on Fusion . And I am sure that a bulk of that research entails more advanced insight into the shave technique and results.

Quite a bit of science remains useful forever. Think about classical physics, which is hundreds of years old. The latest and greatest modern physics has replaced it with relativity, quantum mechanics, and field theory. But F=ma still works just fine for everyday purposes, and even for rocket science.

For our purposes, shaving has not changed much at all since the 1960s. Skin and facial hair have not changed. We are still using water, brushes, soaps, creams, and steel. The latest and greatest research can use newer technology to improve observations: that "trapped hair" study would have been difficult before cheap digital cameras and image processing. We might see refinements of old ideas, and even some new ways of thinking about old problems. But the old research remains as valid as ever, and worth reading.