How to calculate denim shrinkage

Here’s today’s guest entry from Maria Santiago from Tucson AZ who shares what she’s learned about calculating shrinkage for denim. This first part was the email which I included because I thought it was funny, followed by her entry.

Kathleen, here is the article, it’s not super-long, but I think it says everything. I am currently undergoing similar difficulties with buttons. ARRGH!!! I remember when I was still in school, and I bought some books you recommended, “Quality Management in Production” and other stuff like that. I should have been buying “All the Little Intricacies of Buttons” and “A Million Things About Denim You Never Would Have Ever Imagined”. That would have been WAAAAAY more appropriate. Anyway, I am surely not having a unique experience in trying to make a denim company; certainly, other companies exist that are considering making one jean part of their line. I’m sure they could use all my experience to their advantage.

Once I figure out the deal with buttons, I would not mind writing one about all the different things about buttons-for-jeans (shank buttons vs. snap buttons vs. rivets). In fact, I would not mind writing an entire tutorial (in bits and pieces of course, as I figure it out) of what I’ve learned.

How to calculate denim shrinkage
I graduated college a year ago after having spent a semester writing a business plan for a small apparel manufacturing company -a jean company specifically. An economics major, I spent 50 pages talking about employee compensation and incentive; about supply-chain management and benefits above cost; things an economics major would consider the forefront of Important Things in the creation of a company. Well, I was wrong.

Instead of writing about conceptual matters, I should have been learning about practical ones. As a result, everyone at Patternworks is schooling me in the practical matters in making jeans.

Challenge number one involved shrinkage. After I had acquired my denim, my wash-house guy and I set about finding the different colors and shades we could get from the denim with different washes and other processes; when Patternworks asked for shrinkage, I figured I could kill both birds with one stone. With Wash-House Guy, I cut the denim into 20-inch by 20-inch sections, stapled them together into the shape of a pant leg, and washed them (Kathleen describes how to test for torquing and shrinkage in her book) .

I took the raveling squares of denim to Patternworks so that they could calculate the shrinkage from the denim. For many reasons, this was completely unacceptable. First, shrinkage is traditionally calculated with 12.5-inch axes (make a 90-degree angle out of two lines, both 12.5 inches long) because it’s easy to calculate percentage-shrinkages with those measurements. So, the length of my denim squares was incorrect. Note that “length” is defined as along and parallel-to the selvage edge; “width” is perpendicular to the selvage edge.

Then, denim typically shrinks a little bit- not a ton; but approximately 2% – 5%. When you have small shrinkage percentages like these, “a little bit of raveling here and there” actually translates to “we can’t figure out your shrinkage because the raveling is too large relative to actual shrinkage”. I should have made my axes far, far away from any un-sewn edge, so that the raveling would not interfere with my 20-inch by 20-inch (which, of course, should have been 12.5-inch by 12.5-inch) axis.

Denim is composed of little fibers that run both lengthwise, vertical (“warp” yarns) and horizontal, width-wise (“weft”, or “filling”) yarns. These yarns shrink in different ways- due to their weave, the selvage edge, and other factors. Thus, when you calculate shrinkage, you have to account for this and note where the selvage edge is. So, a length of denim, freshly-unrolled, will shrink differently in different sections. Sections closer to the selvage edge will shrink less; sections closer to the middle of the length (between the selvage edges) will shrink more. So, any given length of denim, after having been washed, will have shrunk (minutely) differently, given the “section” it is in, relative to the selvage edge. This is important when you consider the marker that will be made for the pattern. To overcome this, you have to average out the shrinkage.

These are the steps to calculate denim shrinkage:

  1. Lay out a length of denim; 1 yard in length (note: “length” is defined as along and parallel to the selvage edge) should be sufficient.
  2. Make an axis maybe 4 inches away from the top selvage edge; make the vertical axis perpendicular to the selvage edge, and the horizontal one parallel to the selvage edge.
  3. Make sure to label in permanent ink “12.5 inches” on both axis, just in case.
  4. Repeat with the “middle” axes, which should be in the middle of the length of cloth.
  5. Repeat again with the “bottom” axes, which should be at the bottom, maybe 4 inches up from the selvage edge.

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  1. bethany says:

    This is a perfect tutorial for me. I am just introducing a jean to my Fall 2008. Frankly, I would love to hear more about the button issue.

  2. Elizabeth says:

    Ugh, don’t even get me started on school education! I have too many issues to count- but since we’re on the topic, here’s a relevant one. In an era of designer denim, premium denim, denim that lifts/ tucks/ molds your body, finds your future husband and does your house chores too (it’s gotta, at 200 bucks), “Fashion School” taught me NOTHING about denim (OK, they told me the light weight one is called chambray, woo-hoo!). Forget the 500 ways you can rinse, distress, whisk, twist, cut and otherwise mutilate it into a Hawt Item of the Moment, I don’t know anything about shrinkage, torque, and other (First, Second and Third) Eye(s) Opening topics mentioned by you and Kathleen, let alone the glossary of buttons, so please, please, please Maria, do tell us more!!
    I just realized, I’m afraid of denim- where does one start?! Even patterns are different, what are the rules for ease, the crotch depth, the pockets (and WHAT is up with the 5th pocket? Someone please put the rumor to rest, was it really meant for match boxes in the old days? Why do they call it a coin pocket then?). Anyway, is it really possible to get more than one shade/ colors out of the same fabric?? What shade would be the best shade, a medium one? Would you be able to go lighter and darker? Oh, and is there ANY way to get that super sleek dark blue (indigo) to STOP BLEEDING allover the couch, the skin and one’s underpinnings?! That is really annoying and destructive to one’s couch/ skin/ and underpinnings. And why is 12.5″ THE size for testing? What are the proper names of processes used today- if one would look to have whiskers on the front of the pants (I don’t know why they do, but let’s assume they I would too), what kind of contractor would I look for- a Whisker?!! Or the faded look, I’m thinking asking for a Fader might not be the most intelligent thing? Is a Wash- House a company that handles all kinds of denim processes (and only denim, or they can do “cool stuff” with other fabrics?) Or what do they do exactly and would they be able to pre- shrink the fabric? How much of an extra cost would it add, what would be a ballpark minimum and how is the price calculated? Also, is it effective/ worthed? Sewing-wise, what specific machines are necessary, and what do they look like (I so want to go research info on this now). I suppose a shank- snap- rivet button setting artillery is necessary- are those all different machines? I’ve benefited from a grommet setter, I imagine they look similar? Oh, this has to be an easy one, but I’ll ask anyway- what kind of thread is it (fiber, weight, name)?
    Thank you! :)

    • Mary Anne A Krohn says:

      RE: the 5th pocket on a pair of jeans: I believe it’s a holdover from the original jeans made in the 1870’s by Strauss and Davis. The pocket was designed to hold a pocket watch for two reasons: only women wore wrist watches, and most “blue collar” working men of the time did not wear vests to work in, which was the usual “housing” for time pieces for men, along with the chain. Even in the mid 50’s, a lot of farmers, ranchers, and construction workers in the Western town I grew up in only wore wrist watches on Sundays and special occasions, so having a safe place to carry your daily pocket watch was critical. I even remember our elderly parish priest finally receiving a gift of a wrist watch from the parishioners because he was always pulling up his vestment or cassock to pull his pocket watch out of the 5th pocket of his pants or jeans. For us kids, it was pretty humorous to watch!

  3. Todd Hudson says:

    Thanks for the the entry. Is there a sewing contractor in Tucson that does denim? I’m interested because that’s my hometown. Otherwise, I would assume you’re doing your patterns, sewing and washing all in LA. Or Mexico?

  4. Jennifer E. says:

    Great entry – when I did shrinkage testing for a manufacturer I did from selvage to selvage with squares going diagonally across the fabric trying not to be using the same warp or weft yarns; this methodology I was taught in my Textile Science courses. I could get between four to five squares across the fabric. I would then calculate the average shrinkage across the fabric. I actually found the section closer to selvage to shrink more because they have more tension on the warp (length wise) yarns, but that my experience with the fabric I use

    In answer to some of Elizabeth questions
    12.5 ” verse any other number – easy math especially good if you have to do some over and over and over and over again – not that I have any experience with that (2 years, 4 months and several odd days doing this for garment manufacturer on ugly plaids)
    1/8 inch is .125 therefore if it shrinks 1/8 inch is got 1% shrinkage 1/4 2% etc…

    Indigo whether synthetic or natural is oxidized to the fabric and therefore does not bond to the fiber like other dyes there is rubs off – so no not really going to be able to change that unless you do not use indigo but then you can not get whiskering, fading etc.. again basic textile science

  5. Timo Rissanen says:

    Some years ago I worked for a young women’s denim brand – think stretch hipster jeans if you can bear it – and we had a system for testing denim shrinkage that worked for us very well. This is not to dispute what the book says (I got it! I know nothing! I’m loving it!) but I thought worth sharing. Each season we’d use at least ten different denims (of those, at least 90% were stretch, the rest rigid, as we used to call non-stretch fabrics), each with a different shrinkage.

    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 100x100cm 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!

  6. J C Sprowls says:

    I’ve been taught both Timo’s way and the way listed in the post. Personally, I’ve always done it the way it’s done in the post because there are differences along the width of the fabric.

    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.

  7. Kathleen says:

    …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.

    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.

  8. Lily says:

    I’m not in the apparel business, just a customer. How does stretching-out relate to these estimates? One of the biggest complaints of customers is that after a few wears, the jeans that fit so beautifully out of the dryer are now saggy. Likewise, one of the things people love about premium denim (like Paige) is that it keeps its shape wear after wear.

  9. J C Sprowls says:

    I’m out of my depths on manufacturing with denim – at least for now!

    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!).

  10. Trish says:

    I am not sure if this info is valuable but I was taught by apparel industry professionals to calculate shrinkage this way…

    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?????

  11. theresa says:

    This a lay person’s question. I bought two pairs of strech jeans and would like to shrink them a from a size 8 to a size 6. If this is not possile please e-mail with a way I can shrink them the most(of course not ruining them)

  12. erika says:

    Do you know how to calculate shrinkage based off before & after specs of a sewn garment? I hear this is a more accurate way to determine shrinkage.

    • Yes, I can calculate shrinkage based on before and after. I disagree that it is more accurate, I’d think it would be exactly the opposite. Maybe whoever told you that could explain and enlighten us all.

  13. Oscar says:

    I’m a tailor and trying to make made to measure jeans for fussy people. I find this very confusing so my idea is to buy preshrunk material. What I would like to know is what do you call this type of denim. Another way I was looking at is to pre-wash the fabric before you draft it in very hot water. Please advise me if my ideas would work . Thank you

  14. Manik says:

    Read your article on denim shrinkage and found it educative .Hoever it will very useful and educative if you can elaborate exact time duration and temperature conditions in relation to the washing cycle. Regret to bother you and express regret for thhe same.

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