Mechanically measuring shave soap/cream slickness

[olschoolsteel]

Admittedly i have spent a few more yrs on automotive forums than here but wanted to present an idea to the forum in hopes of it gaining traction (pun intended)

I was reading an independant review about oils, viscosities, and brands. On automotive forums, brand and weight of oils can be very polarizing. Much like brands and types of shave soaps.

So this crafty fellow devises a ball bearing that "slides" on a small turntable drenched in the oil type he is testing. It was spun for a specific amount of time, say 60 seconds or so. The mechanism spinning the turntable measured the resistance. The lesser the resistance, the slicker the oil.

I realize a shave soap test would require consistant mixes between the soaps, amount of water, length of time whipping, type of brush, mug mix or scuttle etc.


But......



Could such a test be devised for our shave soaps to provide a consistant and repeatable result, thereby rendering the term YMMV an acronym of the past if hard data can back up a poster when he says "My TABAC soap provides the slickest shave possible!"???


If such a test has been done before, can someone point me to the thread?

 

[aihpcfl]

I think your problem is that even though you can identify important parameters, maybe even all that matter, your test will only be meaningful for the conditions of the test. There's just too much variation in the real world, and that is precisely why YMMV so often applies. Imagine if the same were true for oil viscosity or oil life. These values have useful meaning because the relative ranking in the tests holds up in the real world. I can't imagine a test with soaps and creams where anyone could rely on the ranking to pick the product that would be best for them.

 

[Mandina]

Very interesting idea. I have seen nothing about scientifically operationalizing "slickness." To be sure, it would still come down to YMMV, since the whole of shaving (or of anything else) is more than the sum of its parts (just as the NFL's attempts to isolate and assess component skills of potential draft choices is wildly hit or miss in sizing up a player's true worth). Even so, your idea is intriguing. We B&B members do obsess about making comparisons, no?

 

[mblakele]

By all means give it a try. You may have to find a way to account for variations due to lathering technique, equipment, and water. You could handle the last by always using distilled water, but some folks want to know which soaps work best with hard water too. If you measured soap lathered by several different people using different techniques, you might be able to say whether or not those factors are important.

 

[SiBurning]

I've thought about this. I'm not sure that a direct measurement of friction is even possible. Some kind of empirical approach might be useful, and I'd encourage you to do that and ignore the rest of this post. I have grave doubts about getting hard data.

Would you be doing a direct measurement in an actual shave? If you did, how would you separate the force of cutting the hair and cutting through skin from the normal friction force? And if you don't separate them, just what are you measuring?

It's one thing to measure ball bearings on a defined surface of some known material. But a razor on skin deals with completely unknown materials and surfaces. Trying to duplicate this artificially is rather difficult. There's been work done on creating artificial skin for lab testing, but that approach isn't entirely satisfactory because shaving is actually planing, which is to say you're cutting off as much skin as hair, and I've already mentioned the complications there. There's at least two different cutting modes--slicing through hair and planing skin--and no one really knows what lubrication regime is involved in shaving.

If you already know the basics of friction, you'll find more confusion in Mad Scientist #4: Friction of Wet Skin, Lubrication, and... Probes?

 

[gash]

I've thought about creating something along the lines of a Stimpmeter. As other people have noted, though, there are many important variables in addition to the tested slickness of the soap or cream. Plus, in the end, the shave test is probably all that matters, and if somebody feels that super glue gives them a slicker shave than does Tabac, then so be it.

 

[edgerunner]

It would be nice to be able to measure viscosity of soaps but I don't think you can create consistent controlled samples (lather). Firstly, unlike branded oils, although the product and water can be consistent quantities, mixing time, mechanical process/technique, preparation time, introduced air in the mixture, are all different. Secondly, lather is not a stable substance considering conditions like period of time, humidity, temperature of the environment, and air pressure. Lather properties greatly change depending on these conditions which are different between different home environments and the controlled testing conditions.

 

[Graybeard57]

You all have waaaay too much time on your hands!

 

[MRoney]

Viscosity is a fluids resistance to flow, so if we wanted more viscosity we could just decrease the water added to our lather. Whats really important is surface tension, the higher the surface tension the more protection from nicks. Or at least thats what my understanding leads me to believe. However, if viscosity is wanted, a simpler measurement method would be to drop ball bearings into test tubes containing the liquid to be measured. The longer the travel time, the higher the viscosity. This of course would only work with liquids.

 

[inspiringK]

I'm not sure that creating a test that validly tests lather slickness as it pertains to shaving in real conditions is all that viable.

That being said, I'm sure that a repeatable test measuring lather slickness in general can be created. Since it would be tough to discern just how much the test results would translate well into actual shaving, the value of the tests may be limited.

But, I would love to see the test tried out The example used in the OP actually sounds pretty effective, maybe that same sort of test could tell us something (not everything) about how lather slickness from different soaps compare under ideal circumstances. Yes, there are a lot of variables in shaving and yes we don't all shave under ideal circumstances, but I'd like to see those results nonetheless.

 

[edgerunner]

Viscosity is the less popular term known as thickness of fluids, and depends on the friction between its molecules which in order causes certain resistance to applied external forces. That's why viscosity as thickness is directly connected to the factor cusion of the lather, and the friction is connected to the glide or slickness of the lather. Naturally, if you have great thickness (high viscosity), honey for example, it means you can have great cusion, but not good glide (too much friction). So, lather is supposed to have balanced thickness and friction as per the personal preferences of the shaver. The bottom line is viscosity is the collective noun combining cusion and glide. When I say a soap/cream has good viscosity, I mean that I like the balance of cushion and glide it provides for me.

 

[Quintar]

I actually built a prototype device to do exactly this. I started using cream and weighing out cream and water and trying to determine what cream/soap to water ratio would be slickest for each product...problem is the results were never consistent. I'd put the lather on and measure the force needed to overcome static friction (that was the simplest to measure in the prototype device) and repeat over and over with the same lather and it would never be the same. And it wasn't 10% off or anything like that it would vary HUGE amounts...I think you'd have to develop a special machine to accurately measure an emulsified foam fluid. I tried checking chemical papers but couldn't find anything where people had done something similar....so I gave up

 

[Try em all]

Just off the top of my head, for lubrication, metallic stearates as additive to the shave foam would have the best results. They are used in automotive oils for the same purpose. They are also present in most of our shaving lathers in the form of sodium & potassium stearates.

 

[JBLA]

I think this is entirely feasible.

I'm not exactly a scientist, but I feel reasonably sure that this could be done without undue hassle or expense.

I mean, how hard would it be to take your blender and blend 1/4oz shaving soap with 2 oz water for 60 seconds, then take a board (or a kitchen table for those of us that are bachelors / have extremely understanding SWMBOs), set it at a slight angle, paint the top of the table with the blended foam, set a coffee mug or some other flat bottomed object with a bit of heft to it, and see how far it slid. (If it slid the full length, you'd lessen the angle and try again.)

Wipe off the table / mug between attempts, compare the distances, and I think you'd have a pretty good way of rating the slickness of the soap.

(Rating density / cushion of the lather, etc., would be trickier, but I don't think this would be too hard.)

 

[Col Wilburforce Buckshot]

However, if viscosity is wanted, a simpler measurement method would be to drop ball bearings into test tubes containing the liquid to be measured. The longer the travel time, the higher the viscosity. This of course would only work with liquids.

You have described a rudimentary Baum Gauge. It is used to determine specific gravity.

 

[MRoney]

Ahhh, thanks, I was reaching a bit there. I applaud the OP for the lofty goal. Hope this thread leads to something.

 

[olschoolsteel]

I sure hope I didnt imply that I have the capability to build the device!

The idea grew in me as my AD grew I continue to read countless reviews and sales pitches.

Back on topic, specifically to SiBurning, I think the cutting of the hair would be the hardiest to duplicate. Especially given that hair length and diameter varies greatly between every human. But, making every controllable variable the same, I think it would create a good "baseline" for determining soap slickness, by measuring it's resistance or drag.

 

[ReAndyMator]

Is lather a newtonian fluid? If not you'd also need to check for the shear rate. You'd need something like a cone and plate rheometer http://en.wikipedia.org/wiki/Rheometer#Cone_and_plate

If it isn't, it might explain why some people swear that you need slow strokes, and other insist it's short fast ones. Different lather, different rheometry. In the end, it would all be empirical as to how it actually works **for you**

 

[n2hql]

Too much thinking here. If it works for me, I use it, if not, PIF or trash !

 

[Graybeard57]

Too much thinking here. If it works for me, I use it, if not, PIF or trash !