How to measure a fabric's stretch?

Question

De-lurking for a moment to query the wisdom of this group!

How can I accurately measure a fabric's stretch? I've pulled on 4" and judged the percent (50%, 75%, etc.) but I've been waaay off on several occasions.

Is there, say, an "industry standard" method of quantifying fabric stretch that uses known forces (weights?) or something more precise than feel? Ideally I'd be able to measure and generate numbers by which to compare fabrics. For example, in addition to the total amount of stretch (percent?) I'd like to know the force required to achieve that stretch (to get an idea how tight or loose the garment might feel at that stretch).

Background: I'm sewing cycling shorts and have found (after butchering a few prototypes) that fabric stretch makes a big difference! (no laughing please -- I'm guessing this isn't news to anyone!). :-)

Thanks in advance.

small change · Accepted Answer

You might consider how much negative ease is in your pattern, too.

Me? I use 1" seam allowances and adjust the stretch to my sense of comfort which can vary from the pattern, and then serge seams accordingly. I know from experience that I need to go up one size when using 9 oz beefy lycra, as compared to regular/Italian lycra. Supplex lycra has a lot more give that even that. I know that's not what you want to hear. Sometimes this stuff goes by feel, not by numbers.

My cycle clothing:

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almost_fast · Answer

Great minds think alike! That's what I'm trying to pin down.

More or less what I did while making a few "muslin" shorts using cheap fabric. I *thought* I finally had the alterations right, then I switched to the expensive fabric...

I'm (painfully) gaining similar experience. :-(

Since different fabrics stretch differently, one pattern may not be good for different garments. In addition to shorts (using lycra), I also want to make full- and 3/4-length tights (using something like PowerStretch fleece). Maybe it's really true that I'll have to sew each garment two or three times?

Yeah, but I want the numbers! It's a personality flaw I'm working on. ;-)

small change · Answer

the book, Sewing Outdoors Gear by Rochelle Harper has a negative ease chart in it that is very useful.

Unless you are going to be doing production, I'd recommend the following: Check your flat pattern for alterations and negative ease using the recommended chart. On tights, you'll want to compare numbers for circumference at quads, knee and calves. Check inseam length, and crotch length. Make sure you've allowed for how high or low you want them in the front or back, plus elastic. ( I've used this technique for mail order clients in Europe and never have problems with fit. )

Cut with 1" seam allowance and baste together, adjust fit, then seam. One rule of thumb is that if you are using a more stable stretch like powershield or even powerstretch, is to cut one size larger.

I would think that by measuring your pattern carefully, allowing for negative ease, and following the above suggestions that you will be fine, unless you are particulary anal about things.

you are welcome.

almost_fast · Answer

Thanks for the recommendation -- I've ordered it (and two others!).

Thanks for the thorough instructions, Penny. Good to see that what I've been doing isn't that far off after all... :-)

Wow, only two posts from me, and already you know me so well... ;-) Honestly, I'm working on becoming less anal, but I've got to go about it in *just* the right way! ;-)

How to measure a fabric's stretch?

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