Why do deodorant sticks always become uneven after regular use?

[bluntc0ncussi0n]

I always noticed that deodorant sticks become uneven after being used for a while. It doesn't bother me, but has always made me curious as to what exactly is the scientific process that does something so bizarre yet so interesting. I've always found nature's effects on modern technology as well as humanity itself to be an interesting study.

[Bufofrog]

Your arm pit is concave so the bar wears to a convex shape,

[Phi for All]

!

Moderator Note

Moved from Science Education to Engineering.

 

First you need to establish that this phenomenon happens to more than just yourself. An experiment needs to be devised.

Besides different brands and compositions, you also need to factor in the amount of hair present (and possibly length - does long armpit hair use less product than a short stubble?), as well as temperature and humidity conditions. Does the pressure used affect the wear, and do men and women use differing pressure when applying it? And as Bufofrog mentions, the shape of the armpit is also a factor.

Why do you find this bizarre? As a guess, I think if you experience any unevenness in the application of a product like deodorant, it's most likely because the manufacturer receives no benefit from changing. If you're satisfied with the price, shelf life, and how the product takes care of the problem you bought it for, that's where the manufacturer is focusing their efforts. It could also be that the uneven wear makes you use the product faster (trying to even it out) and purchase more. 

[bluntc0ncussi0n]

On 1/7/2020 at 12:13 PM, Phi for All said:

!

Moderator Note

Moved from Science Education to Engineering.

 

First you need to establish that this phenomenon happens to more than just yourself. An experiment needs to be devised.

Besides different brands and compositions, you also need to factor in the amount of hair present (and possibly length - does long armpit hair use less product than a short stubble?), as well as temperature and humidity conditions. Does the pressure used affect the wear, and do men and women use differing pressure when applying it? And as Bufofrog mentions, the shape of the armpit is also a factor.

Why do you find this bizarre? As a guess, I think if you experience any unevenness in the application of a product like deodorant, it's most likely because the manufacturer receives no benefit from changing. If you're satisfied with the price, shelf life, and how the product takes care of the problem you bought it for, that's where the manufacturer is focusing their efforts. It could also be that the uneven wear makes you use the product faster (trying to even it out) and purchase more. 

That's definitely true. Those are some good points you made. I think you're right in the fact that I would have to do an elaborate experiment in order to accurately figure it out. Of course it may largely be due to the shape of the human arm pit, rounding the shape over time. Thanks for the help!

[iNow]

Could just be how you personally hold the deodorant during application. I’ve never noticed this unevenness your core, yet you’re ready to say it happens with all humans and all deodorants. 

[Phi for All]

16 minutes ago, iNow said:

Could just be how you personally hold the deodorant during application. I’ve never noticed this unevenness your core, yet you’re ready to say it happens with all humans and all deodorants. 

You're right, we need to build an applicator to isolate human influence from the experiment and give us consistency if we're going to get federal funding for this. 

[StringJunky]

You'll hold the applicator and apply it a certain habitual way and after a while it will contour to that routine

Edited January 9, 2020 by StringJunky

[Callipygous]

On 1/7/2020 at 5:50 AM, Bufofrog said:

Your arm pit is concave so the bar wears to a convex shape,

I find that depends. If I extend my arm all the way up my shoulder socket pokes out, effectively changing my armpit from concave to convex. Just another complication for the experiment.