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On the Measurement of Croap Durometer: A New Methodology

To meet the annual continuing education requirements of my BOSC membership, it is necessary for me to either:

1. Advance the science of shaving in some extraordinary or dubious way
2. Provide evidence of unrepentant indulgence in one or more acquisition disorders.

Unfortunately, my spouse has recently discovered the 10'x10' storage unit I've been renting for my shaving necessities, so the latter is not an option at present. Therefore, it must be science.

One problem that I think worthy of study is the firmness of various cremes, croaps, and soaps. Some cremes are firmer than croaps, and some croaps are harder than soaps. Mitchells Wool Fat soap is the only known material harder than diamond. It's gets downright confusing. This would not be an issue if no one cared, but studies show that 0.03% of shavers have a strong preference for a specific degree of firmness in their soaps. Shamefully, manufacturers offer little to no information on this key parameter. It would be helpful therefore to have an easy, repeatable way to measure the firmness of soaps, such that any hobbyist soap hoarder can measure the firmness of soap/croap for the purposes of posting more edifying reviews to this message board.

It's a vexing problem, but fortunately we may stand on the shoulders of giants; the rubber and plastics industry has devised such a tool, which is called a durometer. I have used these devices myself, and find them indispensable. It is a simple tool, that consists of a "needle" affixed to a spring. The tool is pressed down on the material to be measured, and the shore durometer is displayed on a dial indicator. The OOO Scale Durometer would be perfect for this purpose, but sadly many wet shavers do not have this tool in their shaving den.



Thus a new methodology must be devised. I believe that this new methodology should have the following characteristics:
  1. Measurement should be on an interval scale (not ordinal or nominal)
  2. It must use only household materials costing in total no more than $1.00
  3. It should be possible to make the measurement apparatus in less than 5 minutes
  4. Individual measurement should take no more than 10 seconds
  5. Accuracy must be +/- 13.7%
Sadly, I have no such methodology, nor do I have any good ideas on how it might possibly be done. Please help.
 
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TLDR:

"Croaps" range in firmness from something more akin to a hand lotion, all the way to the consistency of a frozen crayon. That is stupid. I'd like a way to discuss the firmness/consistency of croaps and soaps with more descriptive terms or better yet a quantitative scale. Any thoughts?
 
You might be unto something huge here!

Once found the methodology and measuring scale, it can be taken to a further level by representing the values and offer suggestions on what kind of brush is better suited to use for a specific soap/croap.

That in itself represents another problem to be tackled as brushes will also have to be categorized on material/firmness/water holding capacity/floppiness etc.etc.etc.

Also we will have to categorize type of face/beard/growth/geography in which specific soaps/croaps and brushes can have optimal performance and provide specifically designed products/combinations for customers and their very specific wants and necessities.

A new research and development branch with a military budget size might be required!
 
You might be unto something huge here!

Once found the methodology and measuring scale, it can be taken to a further level by representing the values and offer suggestions on what kind of brush is better suited to use for a specific soap/croap.
These are very good points. I can see that you are a scientist yourself.

Alas, throughout history countless projects vital to the advancement of humanity have been laid low by "scope creep". We must not the perfect become the enemy of the good!

Therefore, I say that we must restrict our aims to specific requirements enumerated 1-5 above. We need a simple device that can measure how "firm" a croap is, using common household items.

But how? 🤔
 
Just to get the brainstorming ball rolling, all that is really necessary is an object everyone has that is of uniform shape, and a means of applying pressure/force that is also uniform. It could be as simple as a specific weight if water on a marble (though that is too inelegant to contemplate seriously, and almost certainly insufficient to renew my membership in the BOSC).

But how?
 
How about this crazy idea ...

Measure the soap volume (volumetrically, e.g. place in liquid and measure displacement volume) perhaps using satellite soap (that is if you are worried the volumetric measurement is going to mess up below, just take the measurement of a different soap):

Place soap on the bottom of a tall tube and drop either pointy or round objects on soap from top of tall tube, perhaps say X times for good measure.

Remeasure volume by displacement so the delta volume gives you a sense of the hardness.

The other one that might be closer to the Durometer is if you drop the pointy needles in a way that its directionally down, since you are dropping from the same height, I think the depth of the embedding will give you a sense of the hardness?
 
The other one that might be closer to the Durometer is if you drop the pointy needles in a way that its directionally down, since you are dropping from the same height, I think the depth of the embedding will give you a sense of the hardness?
Yes. I think this describes both the problem and the solution precisely. The measurement must be a quantifiable force over a quantifiable surface area.

The trick is to use household objects that everyone has, and which are of uniform shape, and weight and that satisfys requirements 1-5 above.
 
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Yes. I think this describes both the problem and the solution precisely. The measurement must be a quantifiable force over a quantifiable surface area.

The trick is to use household objects that everyone has, and which are of uniform shape, and weight and that satisfys requirements 1-5 above.

Darts??
 
How about a hard plastic straw of uniform length and say a weighted needle you can drop thru the straw?

The needle would have to travel straight thru the straw at uniform speed every time so the dynamic force applied is the same for each croap tested and then measure how far is embeded as @Avi mentioned above.
 
The needle would have to travel straight thru the straw at uniform speed every time so the dynamic force applied is the same for each croap tested and then measure how far is embeded as @Avi mentioned above.
Well done. That's idea 1!

What's idea number 2?
 
I think acceleration adds a potentially confounding variable. However that's idea number 2. Worth considering!
 
Drop a 9/16 glass marble down a nearly vertical empty paper towel tube touching the surface of the soap. Measure the depth of penetration into the soap surface.

:smartass:
 
I think acceleration adds a potentially confounding variable. However that's idea number 2. Worth considering!
Oh I see due to air resistance or even due to friction against the edge.

The other simple variations of this that are starting to feel like a school project, is you can mount a needle or a razor blade on a toy car and roll it down a ramp where it plows into the soap needle first. The acceleration and hence the force would be dominated by the mass of the car and so reasonably effectively a constant if the toy car is heavy enough and the wheels aren’t crappy. That also removes variability in the weight of the razor blade etc ?
 
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