Take a piece of fabric about 12″ X 12″ or a little larger. With an wash-fast marker, make a 10″ X 10″ square, making sure to note the straight of grain. After all washing, drying (and any other laundering steps) remeasure what is left of the 10″ X 10″ square and calculate the percent of shrinkage by subtracting the new measurement from the original 10″ and dividing the difference by the original 10″… make sure that you clearly note the warp and weft shrinkage.

When it comes to shrinkage being different at different ends of the bolt, could this come from the stretch that was added to the fabric as it was wound onto the bolt? Or does this have something to do with the weaving?????

http://www.hancocks-paducah.com/item–i-OG-SQ.html
It is only $13.49.

But, to address the question re: ’sag factor’. I presume that a designer would need to commission a weaver, specifically, with very specific tolerances on the fabric. I know shrinkage can be enforced at the mill - presuming your volume is sufficient to make sense.

Shrinkage is a factor of stability or distortion, which are criteria by which the quality of goods are measured. Since these things can be measured, they can can also be managed. Solutions may already exist or they may need to be developed. The most qualified person, IMO, to speak on this is an experienced denim weaver.

RE: AAATC. I’ll need to pull the book. I’m confident it says 3 cycles. My memory could be playing tricks on me, though. So, I need to check myself. I’ve always done 5 cycles for raw & finished goods because that’s how I was taught. Training and experience continue to support that theory, so I saw no reason to change.

It’s interesting there is a whole variety of other tools available. Until now, I’ve always been - decidedly - low-tech, emulating the End User. For specialized tests, like flammability, abrasion, tensile strength, chemical exposure, etc. I know to use a lab (guess it’s time to add one to the Rolodex!).

I don’t want to get unhinged but this touches on one of those entries I never published because I thought it’d annoy or be too boring (Danielle has told me I have to stop saying that but I really do worry I’ll bore you).

You mention AAATC recommends 3 washings…as far as I’ve been able to determine, the commercial machines for testing shrinkage are designed to mimic the effects of *5* washings (in one load) so it’s odd AAATC says three. I guess commercial interests can (sometimes?) follow more stringent guidelines.

Re: shrinkage calculators, again, I never published my entry on this but there are rulers you can buy for this purpose. They’re pricey tho, some $80+ for a metal rule. I’ve found sources here (scroll down, under “templates”) and here (UK, M223C Stability Template and Shrinkage Rule). There’s also mention of a patent for one but no illustration. I know there’s ways to download patents but I never remember off the top of my head. I’d also found instructions for a detailed method (illustrated) to specifically measure the shrinkage incurred when fusing but that’s on my home computer. It is definitely not a process you’d figure out without a long trial of experimentation. Gee, if I’d known anyone was interested, I would have published it months ago.

This reminds me, if you’re in the market for any high level technical research papers, access to Sage Journals is free until the end of this month. Spend some time browsing and downloading while the opportunity lasts. They have tons of apparel and textile related science stuff.

With custom clothing - I’ve mentioned this before - I pre-shrink the goods. AAATC recommends reporting test results after 3 laundry cycles, I prefer 5. So, when I say “pre-shrink” I mean 5 laundry cycles are applied before the goods ever hit the table.

RE: testing. I don’t recall anyone talking about testing the finished garment - at least not in casual conversation. We certainly tested all new styles before they went into production. We did this at the uniform company I worked for in college and I do it with all prototype garments I have made, since.

First rule: NEVER believe the shrinkages that the fabric supplier gives you. We found that these NEVER related to the real world.

Actually, that’s the only rule. We always ordered an extra metre for testing, and would cut a 100×100cm square. Apologies for the metric, but it worked beautifully with percentages. We’d overlock/serge the edges and then measure each of the edges again (to check if some had got cut off through overlocking) and write the measurements on the square with a water-proof marker - usually on the reverse for better legibility. We’d then send it to the laundry that treated all the denim, and got them to do whatever it was we planned to do in that particular denim (e.g. enzyme wash, stone wash, etc.). When the square came back, we pressed it, measured it again, and worked out the shrinkage percentages for warp and weft. We’d then digitise the jean pattern and apply the shrinkage on the computer. Then the sample would get cut and made, and sent to laundry. This worked a beauty with one exception.

We cut our waistbands correctly (see the post by Kathleen; cutting the waistband on the same grain as the rest of the pant) but these never shrank as much as the rest of the pant. I don’t know if it was to do with all those stitchlines, or bulk, or what, but almost always we had to take the waists in, despite the pre-shrink patterns being correct.

Couple of things everyone should know about stretch denims:
If the laundry washes them at too high a temperature, the elastomeric will ‘die’ and lose its ‘grip’ on the weft yarns; the jeans will relax and grow up to a size and no longer be stretchy (this only happened once that I remember, and the laundry actually refunded us fabric costs). Also, although most fabrics tend to shrink more along the warp, the stretch fibre in the weft yarns shrinks a lot (think elastic, and how it shrinks) and therefore an average pair of jeans were up to a size bigger before laundry.

Finally, despite the testing, sometimes production turned into a nightmare as some stretch denims varied quite a bit in the way they shrank. Two rolls of the same fabric could shrink quite differently, and sometimes (in one denim we used season after season, this was a rule) the two ends of the same roll would vary significantly in the way they shrank. The company produced half-sizes (i.e. 1″ increments in the waist measurement) and this worked to our advantage when there were problems; we simply relabelled the pairs that had shrank too much or little.

Not sure if this is any help; good luck!