[jstanley]

> we have learned through firsthand experience many of the variables behind bra-making. I will name a short list:

> [...]

> Temperature of the measuring tape at time of measuring

Are you sure?

If the measuring tape is made of steel, it expands by a factor of 13e-6[0] for every degree C that it heats up. If you measure first with a 0 degree C tape measure, and then with a 100 degree C tape measure (both of which are absurd and will be extremely uncomfortable), then the second measurement will differ from the first by a factor of 13e-4. A measurement of 100mm will become 100.0013mm. Can you even cut the fabric precisely enough for that to matter?

[0] http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/thexp.html

EDIT: But see replies below: it's more likely that the temperature of the tape causes changes in the shape of the skin.

EDIT2: Also just realised I initially missed out the second factor of 100, so it becomes 100.13mm instead of 100.0013mm, which is almost close enough to matter, but only in the extreme scenario of 100 degrees C change in temperature.

[yodon]

The point of the article was that they were doing engineering for and about people. How the body responds to a cold tape undoubtedly causes much larger distortions than the thermal expansion of the tape itself.

[JoeAltmaier]

Nobody measures people with a steel tape? Its cloth or plastic.

[jstanley]

OK, my mistake. To me, a tape measure is a steel thing that coils itself up. Let's try and find some numbers for cloth and plastic:

https://www.engineeringtoolbox.com/linear-expansion-coeffici...

ABS heats up by a factor of 100e-6 per degree C. The largest number I spotted was paraffin with 106e-6 to 480e-6 per degree C.

If the tape measure is made of the most-expanding type of paraffin, which is itself the most-expanding material listed, then the 100mm measurement becomes 100.05mm when heated by 100 degrees C. I really don't think a difference of 50 micrometres matters, or is even achievable, in the manufacture of a bra.

EDIT: (But I see the other points now - it's not the thermal expansion of the tape, but the body's reaction to the temperature).

[jschwartzi]

Intercostal muscle tension probably has a bigger effect than thermal expansion of the tape. The intercostals are the muscles that control how close together your ribs are. They're auxilliary muscles for breathing. Diaphragm and core muscle tension will also have an effect. Your pectoralis muscles and trapezius and deltoids will all also have an effect. These are all muscles that control the size and shape of your ribcage. The human body is not a static shell, but flexes and changes shape depending on the tension of different muscles.

When we touch cold things to our skin, we naturally tense up. If your intercostals, diaphragm, and core are tense when you're being fitted for something that is snug against your chest, then when you get it out of the box it will be too tight.

[diminoten]

> To me, a tape measure is a steel thing that coils itself up.

So like, when you're talking about or to someone on a topic where you're not even sure about the basics like, "what kind of tape measure do they use?" I would urge you strongly to go into "information gathering" mode, rather than "correct perceived incorrectness" mode.

[thomasahle]

Who measures people with steel measuring tape? That sounds very cold on the skin. I'm pretty sure plastic or cloth will be more common.

[Hasz]

I would guess measurements will change based on the skin's reaction to the cold temperature, or the person unnaturally tensing up, assuming we're talking about steel tape, which is very unlikely.

The better bet is that the tape they're using is made of plastic, which is going to deform much more.

[jstanley]

Aha! Thanks. That makes much more sense :)

[0ld]

> If you measure ... with a 0 degree C ... will be extremely uncomfortable

I believe that's all the author wanted to say

[cimmanom]

Effect on nipples?