# Pop Quiz: Does fiber content affect fabric weight? pt.2

Okay! Following up with part one, we had several good responses. The first closest answer was from Stu (no surprise there) who said “everybody is right -kinda”. Okay he didn’t really say that but he sorta did. Summarized, Stu says that the correlation between fiber content and weight is too small to expect controlling for fiber content to be sufficient to control fabric weight. Here is Stu’s quote with all the math stuff (yay math!):

Karen is right, but so is everyone else at her company. Fibre composition does affect weight, but it’s a minor factor compared to other things.

Keeping all other factors unchanged, changing from 90/10 to 80/20 poly/cotton will only increase the fabric weight by one percent.
Polyester specific gravity 1.28
Cotton specific gravity 1.54
.9*1.38 + .1*1.54 = 1.396
.8*1.38 + .2*1.54 = 1.412
1.412/1.396 = 1.011
Actually — again keeping all other factors unchanged — a 100% cotton fabric is only twelve percent heavier than a 100% polyester fabric. So changing the poly/cotton proportion can’t have a bigger effect than that.
1.54/1.38 = 1.116

On the other hand, increasing the yarn size or the ends-per-inch by 10% (holding all other factors unchanged) will increase the fabric weight by ten percent.

So it’s not that there is no correlation between material breakdown and weight; the correlation is simply small. Or stated differently, controlling the fiber content in isolation is completely insufficient to control fabric weight.

I told Stu he won the prize we were giving away but he says that’s not why he entered and it should go to somebody else. This means I had to do a drawing of responses that were aligned to his argument even if the answer wasn’t quite as precise. The winner of the drawing is: Clara Rico! Yay!

Before I forget, I seem to have a mail problem. I don’t know how much of what I’ve sent out ends up where it should be and anything not sent to me c/o fashion-incubator.com is dicey and evidently has been for at least the past few days. So, if you need to email me, send it to KathleenATf-i.com (you can fill in the url or copy and paste it). Thanks!

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1. Clara Rico says:

Yay! I was sure that Stu would have been the winner. I’m quite pleased to be the consolation winner. I looks to be a good book; can hardly wait. Thanks.

2. Quincunx says:

Is anyone else getting the format of this particular post broken (the column isn’t a column, the width is far too wide thanks to the inset of Stu’s post with the RSS icon attached)?

3. sfriedberg says:

Quincunx, yes, using Opera 11.61. The actual post is OK, but the left margin on the comments is way over to the right. Problem doesn’t go away with “fit to width”

4. Kathleen says:

I logged in from my tablet to try to fix it but no go. Hmmm. Will look at it as soon as I’m dressed.

5. I was seeing the same problem as everyone else from my iPad this morning, but now, at work on my very conventional PC, it’s fine.

6. Kathleen says:

I fixed it, probably while you were on your way to work. I had an extra div tag.