Pants/Trousers Wrap – Flattening & Tweaks

So now that you have your cling film + clear tape pants wrap, let’s talk about flattening the wrap, converting it into pattern, & tweaking the muslin(s). While everyone’s body is slightly different & not all my learnings may apply to you, hopefully my notes will help you figure out how to turn your wrap into usable tight pants pattern.

As mentioned before, if you wrapped both legs, to keep things manageable you may want to start with just one side (left or right) – maybe the bigger side. If this one side works well for both legs in your muslin, then you’ve saved yourself unnecessary extra work. If it doesn’t fit as well on the other side, then convert that side into pattern as well & make up your asymmetrical muslin to see if that fits better. If it does, you will have to decide how much effort you’re willing to put into making your pants and what minor fitting flaws you’re willing to live with: If perfection is non-negotiable, you’ll have to make asymmetrical pants. If minor fitting flaws are acceptable, go with the better side or try an average (line in between the lines of your two sides) to see if that fits even better.

Now the flattening process itself, let’s start with my biggest lesson:

Darts better than Princess Lines for flattening

For normal pants at least. Unless you plan on making all your pants with princess seams, don’t cut your wrap apart on the princess lines like you might with a bodice wrap. Because if you do, when you put the pieces back together to form your front & back pattern pieces you’ll inevitably add ease along the curved princess lines like this…

See the big gap / fisheye dart at the back thigh? If you don’t sew it up, it will cause saggy back thighs. This ease allows the pants leg to hang away from your back thigh, making the length along the back princess line slightly too long. You can see the excess length in my Wrap 1 Pattern 1 Muslin 1 below. When I sew the princess seams up (remove the ease), then the back looked fairly good. But as I don’t always want princess seams in my pants, I tried to pivot some of the ease into a bigger waist dart & remove a bit more from the side seams & crotch/inseams. The result looked and felt awful.

Which is why I had to pester MR to wrap me again. For Pattern 2 I tried a different approach and refined it a bit further in Pattern 3. Both of these were based on Wrap 2.

  1. Preserve the princess line lengths by slashing a whole bunch of darts along the side seams & inseams/crotch instead.
  2. To flatten the wrap, let these darts spread or overlap as needed.
    • Pattern 2: I initially tried to keep the marked princess line on the straight grain. This resulted in different spreads/overlaps on the side seam vs the inseam. It might have skewed the angle of the legs, which may in turn be partly responsible for extra wrinkles on the back thigh that I just couldn’t get rid of. So not recommended.
    • Pattern 3: This time I kept the spreads/overlaps the same on both side seam & inseam -ie balancing on the mid-point between the two seam lines which may be slightly off to one side of the marked princess line. This approach seemed to work out better with less back thigh wrinkles.
  3. Next tally up the spreads & overlaps along the side seam & inseam to see if they have become too long (excess) or too short (shortfall).
  4. Correct the excess/shortfall to restore the original side seam & inseam lengths while making sure no extra length is added to the princess lines – especially on the back:
    • Overlap excess/spread shortfall as necessary. This can be above, below, and/or at the leg-bum crease depending on if the excess/shortfall is in the torso or leg portion or both.
    • Above the legs, excess/shortfall can also be pivoted to/from the waist dart.
      Remove excess length by pivoting the side seam/crotch dart into the closest waist dart. This removes the dart in the side seam/crotch & make the waist dart wider.
      Add shortfall length by pivoting the closest waist dart into the side seam/crotch overlap. This removes the overlap in the side seam/crotch & make the waist dart narrower or close it completely.
    • If necessary to preserve the back princess length, you can overlap back inseam up to an extra 1/2″.  A slightly shorter back inseam is one method some tailors used to improve the fit of closing fitting trousers (see Cutter & Tailor’s thread on German slim cut trousers ironwork , another debating where ease & shaping should be, & Canadian tailor Jeffery Diduch’s explanation for why he does these ironwork shaping.)
    • In my Pattern 3 front, I only needed to pivot a crotch overlap into a waist dart. The leg portion had no excess or shortfall. The back was more guess-work: The leg was 3/8″ too long & the torso side seam & crotch also have small darts at the hip level which I didn’t want to pivot into even wider & deeper waist darts. I experimented a bit to see what would preserve my back princess length the best. The result was overlapping at the thigh line the leg excess (3/8″) + extra 1/2″ on the inseam. This leave a 1/2″ fisheye gap at the bum crease which is compensated by a 5/8″ fisheye overlap when I close the hip line darts. So princess line 1/8″ shorter. I can live with that. Interestingly even with the extra 1/2″ overlap on the inseam, my back inseam ended up only 1/4″ shorter than the front.
  5. If the crotch sticks out too much over the leg inseam, slash the lower crotch curve from the bum crease end, leave hinges on the crotch line, & spread/reshape the crotch curve so that the end point of the crotch curve doesn’t stick out too much & you’re able to smooth the inseam line without adding too much ease to the thigh.
    • I didn’t have to do this on the front thanks to the less faithful 2nd layer of wrap I did for the front crotch. But my back had this problem, and I ended up with a weird back crotch curve & shaved 1/4″ off the back crotch length at the thigh. I tried to make sure this new back crotch curve is close to but doesn’t dip below the back thigh/bum crease line. For such tight trousers I didn’t want there to be too much nor too little fabric in that back crotch area.
  6. Add ease below the calf so that the hem is wide enough for your feet to pass through (measure the circumference around your heel to front of ankle then back to heel).
    • Mine was only added to the back to de-emphasize my big calves.
  7. Establish the grain line: I’m not entirely sure the correct method that will work for everyone. Standard advice for slim pants is to fold the pattern pieces in half lengthwise from knee to ankle. The straight line that continues up from this foldline is the straight grain line. But one source I found claims that this may not work if you have knock-knees or bow legs.
    • Note that your hip line for this tight-fitting pants will probably not be on the cross grain, especially in the back. It will slant up on the crotch end, & more so in the back than the front. Front may be close to or even on the cross grain. I’m guessing this prevents the front & back legs from being on drastically different grain which may cause twisting in the leg due to the different behaviour of the fabric at different grain?
    • Pattern 2: This was before I researched the “correct method” – me bad. I used the thigh line as my cross grain & a line perpendicular to this cross grain that run through the centre of the knee as my straight grain. It was at a slightly different angle to my marked princess line as well as to the mid-line between the side & inseam. Maybe this incorrect grain is partly responsible for the back thigh wrinkles that I couldn’t get rid of?
    • Pattern 3: I tried the “correct method” and it worked out better for my legs, which are relatively straight though my knees do rotate slightly inward.
  8. Establish match point notches: If your back inseam is shorter, the stretching should be in the thigh length & not from the hem up. This help the tight pants mimic the actual shape of the legs along the princess lines – back thigh generally shorter than front thigh, whereas below the knee the back is actually longer than the front because of the calves. In fact, this is true of the side seam as well. And the tailoring references mentioned above do stretch & shrink both the side seam & the inseam in different places. Mr Diduch even says that in their factory “to control the amount of stretching and shrinking, we shift the knee notch up by 1/4 to 3/8 inches on the back panel- this has the effect of introducing fullness into the calf area and shortness in the back of the thigh. When we press the seams open and crease the trouser we then stretch the back thigh and front calf, eliminating any ripples of fullness in the seam and doing the same shaping.” So establish your match points for the legs:
    • Top: thigh/bum crease line at the side seam, crotch line at the inseam.
    • Bottom: hem line for both seams.
    • Middle: either use the front knee line making sure both seams below this line is the same length on front & back (ie shorter back inseam is only above the knee), or move the back knee match points 1/4-3/8″ up on both seams as Mr Diduch suggests.
    • Pattern 3: This was before I found the tailoring references. I moved my back knee match points up 1/2″ on both seams. I saw that my back knee guide lines was actually 1″ higher than the front & was worried without some manipulation there would be too much lengths in the back thigh causing fabric pooling there, while there won’t be enough length for the back calf causing dragline there & raised back hem. So the 1/2″ was a compromise because I wasn’t sure I could stretch the relatively straight grain of the side seam & inseam too much. Also, I moved the knee match points to below the knee rather than kept them at mid-knee, again trying to cox the fabric to mimic my curves.

So here are my muslins for Pattern 2 & 3 before the fitting tweaks, plus Pattern 1 muslin for comparison.

While not perfect, I think both are better than Pattern 1 muslin without the princess seam sewn up. So I think the darts flattening approach definitely worked better for me than the princess seam flattening approach.

Muslin Tweaks

Both patterns based on Wrap 2 had similar problems in the crotch area. I managed to fix the crotch area with Pattern 2 tweaks, but it resulted in slightly different left & right – a pain for further pattern designs. Pattern 2 muslin also had a bit more problem in the legs which I just couldn’t get rid of. I made 3 muslins in total for Patter 2 & each had mini tweak experiments – 10 photographed tweaks in total, some of which made no difference & were ditched. Here’s the last of the Pattern 2 muslins:

Pattern 3 was started after I gave up on Pattern 2 muslin tweaks. Thankfully there was less problem in the legs. So I focused on the problem in the crotch area that appeared in both patterns, copying & comparing Pattern 3 to my fixes to Pattern 2 as shortcuts, but tried to avoid asymmetrical left & right. Please note that although I’m summarizing the tweaks by symptoms, the fixes were in done different order & some may have only worked in conjunction with other tweaks (see photo sequence below the tweaks summary). In other words, it’s not a straightforward process. So have patience when you tweak your own muslin!

  • Front crotch wrinkles & pool of fabric (camel toe?):
    • I did try Fashion Incubator’s fix for camel toe by scooping out the front crotch – ie moving some width from CF to the side seam. But it didn’t fix my problem (sorry didn’t take photos).
    • From Pattern 2 muslin, I knew that taking a horizontal wedge out at front hip level tapering to nothing at side seam did the trick for me, so that’s what I did again. Perhaps my wrap had wrapped in a pre-Xmas feast – my front hip line was slanted up at the CF in the trace. Or maybe it’s just that the undulating landscape in my front leg crease created more surface area in the wrap than the fabric can handle. Anyway, the wedge removed basically brought the hip line down so that it’s on the cross grain.
    • Also comparing to Pattern 2, Pattern 3’s front dart was not as deep, hip width a smidge too narrow, & inseam a smidge too long. So a smidge width was added to CF (which now falls right in between my Pattern 2 left & right CF crotch lines), the dart deepened, & crotch point lowered a smidge to match Pattern 2.
    • The resulting fix looks a bit like the opposite of Fashion Incubator’s fix for camel toe. So maybe my unsightly front crotch problem wasn’t a real camel toe even though it looked like one.
  • Minor excess fabric in back crotch area:
    • From Pattern 2 muslin, again it seems like for the best tight-pants fit my hip level should angle up about 1″ at CB crotch. Pattern 2 muslin had a bit more excess fabric below the bum, which is why I tried taking a wedge out (like with the front) & discovered this fix. But note that the fix didn’t properly worked until the front wedge was also removed.
    • Also pinched out CB a bit which resulted in a deeper scoop at back crotch. This lifted my aging droopy bum a bit, minimizing that coach-potato-bum-spread look, & seemed to improve that pooling of fabric under the bum a tinsy bit as well.
  • Legs too short:
    • Maybe the wrap was a bit short to begin with as it’s difficult to cover the ankle bone which goes below where the feet jut out of the legs. The tight fit + knees bent as you walk + my big calves also probably push up the hems a bit (& deposit the extra wrinkles at the knees). The legs were lengthened by 2″. Not sure the extra length will be needed if the legs were widened.

And the actual order I did these tweaks, or at least the ones I remembered to take photos…

Where next

Maybe a wearable muslin in heavier fabric? My muslins so far were made from old sheets, so have no stretch & are perhaps a bit too light-weight for tight pants. This could have caused some of the wrinkles you can still see at the front crotch, under the bum, and around the knee areas in both front & back. Then again maybe my lower body is just impossible to fit perfectly in non-stretch fabric. Or I’m just no good (yet) at pants fitting! Anyway, I’m calling this GOOD ENOUGH & hoping it’ll look better in heavier fabric.

Hopefully this 0-ease Pants/Trousers Block will work for jeans in 100% cotton denim or other mid- to heavy-weight stretch woven. But it probably won’t work so well for stretch denim with 2% or more of elastine – especially not the light-weight (<10oz) jegging variety: Most of the jeans patterns for stretch denim seems to have at least 1″ of negative ease.

BTW why do denim stretch out over time? A “denim expert” from Baldwin Denim said in an GQ article that “dry, 100% cotton denim expands anywhere between 1 to 1.5 inches over a 3 month period of daily wear.” Closet Case Files’ post on sourcing denim says that’s because the twill weave relaxes over time. Do other twill weave fabrics “relax” & stretch out as well? And if I plan on washing the jeans in luke warm water & hang dry, do I still need to pre-wash & dry the denim 3+ times? (Trying to do my bit for the environment!)

I will also need to modify this block to make looser Pants Blocks like…

  • Slim Pants Block that doesn’t hug the bottoms so tightly
  • Loose Pants Block that hang straight down from the hip at the back

For these I’m sort of applying the theory outlined in Catfork’s Work-In-Progress PDFs on “Drafting a slim-pant block (basic pattern) from a skirt block”.

So the self-flagellation quest for the perfect pants/trousers patterns marches on! 🙂

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8 comments on “Pants/Trousers Wrap – Flattening & Tweaks

  1. I always enjoy reading your epic research projects and think it is incredible the amount of work you do and freely publish so people can follow along and learn from your experiences.

  2. Thank you for such a detailed tutorial on making a wrapped pant block. This is one I’m definitely going to try. As I started reading I thought of the the Cutter and Tailor reference to ironwork in achieving a better pant fit and then you referred to it also. Certainly some fabrics accept shaping more easily than others but I’m experimenting with the concept. It does make sense that you can’t fit a three deminsional body with a two deminsional shape, hence the need for additional shaping with ironwork. I’ll be watching for your next steps.

    • You’re very welcome! I guess part of the lesson is pairing fabric with the right pants fit, eg non-stretch fabric that can’t be shaped with looser fitting pattern. Sometimes we just expect too much of fabrics don’t we? I wonder if there were any tradition of more seaming for a closer fitting pants like we’re used to for tops & dresses. Hope if & when you try the wrap you will also share your experiences on your blog!

  3. Your final muslin is pretty flawless. How is the sitting/bending ease? You don’t have any fabric under your tush so I would be concerned about that with a non stretch fabric.

    I wouldn’t lose sleep over the lines around the front crotch. I have them on almost all my (obsessively fitted) Gingers and I think it’s normal on really slim fitting pants. Sometime horizontal lines can indicated the hip being too tight so you could try letting out the hip and see if that works but honestly? THEY’RE GOOD. MOVE ON. 😉

    • Nay, this is standing only pants! OK, I can just about walk in them. But definitely no bending down or sitting 🙂

      I’m hoping it will be ok in stretch woven. Not sure about stretch & non-stretch denims. Only considering non-stretch denim because of what people say about denim stretching out with wear. But maybe even then I do need tiny bit of positive ease? After all, your Morgan BF jeans pattern has 1″ ease. Is that design ease (BF style) or wearing ease? (Haven’t done enough reading about denims.)

      The front whiskers I think you’re right. When I did let out a bit more at front crotch I got sagging shadow. Looking at fashion photos of tight jeans it does seem most have the whiskers. So am hoping in pants weight fabrics it’ll just look normal.

      • Anon says:

        The whiskers on the front of your pants, although minor, are a result of two issues:

        1. it’s pulling horizontally across the front of your hips/thighs because there is not enough fabric horizontally.

        2. it’s bunching vertically, because you have excess vertical fabric.

        If you make your front crotch curve more shallow in the places where there are whiskers, you will gain the needed horizontal width. At the same time, you will be decreasing the vertical length because you are decreasing the curve. If that doesn’t make much sense, Cation Designs discussed something similar here in figure #1: http://cationdesigns.blogspot.com/2013/09/pants-pattern-alterations.html.

        Crotch curves are pretty sensitive, 1/8″ might be all it takes, so you should be able to test this out pretty quickly with your existing muslin by just sewing a slightly shallower front crotch curve into the seam allowance in front.

        • Thanks for the tips. I tried letting out/making the curve 1/8″ more shallow, but got Georgia O’Keeffe crotch instead. Too shy to show }:-) Maybe the muslin fabric is too lightweight. Will try again with heavier weight fabric.

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