The mystery of the back crotch wrinkles, finally solved
In the last instalment of this series a liftetime ago, I field-tested the pants pattern I made from my duct tape shell – and found the same crotch wrinkles in all the test pants that I found in my ready-to-wear pants.
This time, I’m going to fix the problem, and share what I learned about the (extremely common) reason so many people experience this exact same thing. Even people who have completely different butt and hip shapes from me!
Plodding on along
I won’t lie, the upcoming part was a right old slog.
So if you’ll recall, I was cutting my pattern out in test fabric, making adjustment after adjustment, and having photos taken from behind me after each alteration (since I had to be standing straight without twisting so as to avoid distorting the fit).
I pinned, prodded, took in, let out, and ad nauseam. Poor Felix had to take gazillions of photos, and listen to me say things like “Nooooo! Why is it doing that all of a sudden?” And “Who needs pants anyway? I can totally wear skirts when it’s minus 20 degrees out!” I tried what felt like ALL of the alterations. And those #$**@!* wrinkles would simply not go away.
I looked through pants fitting guides, I checked out multiple commercial pattern crotches for clues, and I looked up countless photos of other people’s efforts at pants fitting. That’s when, to my surprise, I discovered that I wasn’t alone in experiencing this particular fit problem.
The moment of epiphany (in which Aunt Kitty mentions unmentionables)
In fact, loads of ordinary photos posted by normal people for, say, online pattern reviews, quite often showed the same rear crotch wrinkle pattern, to varying extents.
But these were people with very different body shapes, sizes, and proportions! Full and flat buttocks, wide and narrow hips, muscular or thin thighs — I couldn’t see a correlation.
Then something suddenly struck me. When you look at a normal pants pattern’s front and back pieces next to each other, you can see that they assume that your front and back crotch curves are level with each other and relative to the ground.
I know this is super-confusing, because it requires you to understand negative spaces, which isn’t intuitive to most of us. Take a look at the drawing below:
This shows the back and front crotch curves of the pants pattern, and the spaces where your body parts are supposed to go (your pubis in the front and your buttocks in the back, labelled in red). The blue line shows you that the bottom curves of the front and back crotch are more or less level with each other on this imaginary pattern. But this is NOT how loads of people are built!
Now, try this with me, even though it’s going to sounds pretty weird: cup your left hand over the bottom curve of your butt, and your right hand in front over where your pubis starts to curve out from your body. Then look in a mirror sideways, and check if one hand is significantly lower (closer to the ground) relative to the other.
No, I’m not showing a picture of this, because we’re keeping this family-friendly. We’re trying to find the body parts that correspond to the pink arrows in the drawing below:
If you’re anything like me, you left hand is noticeably lower than your right. In other words, the bottom of your buttock curve sits lower on your body than the corresponding front curve of your crotch.
This is sometimes called “low buttocks” in pattern adjustment guides, and can be due to lots of different things, such as the action of gravity on a large tush or (as in my case) the tilt angle of the pelvis. It doesn’t necessarily have anything to do with the shape, size, width, or protrusion of your bum.
I’ve since learned that this is pretty common, which is why I saw those same rear crotch wrinkles I had on so many other people, who otherwise looked nothing like me in the butt department. Turns out it’s not due to the strange shape or flatness of my rear end after all!
So how do we fix it?
Fix the pants pattern, I mean, not my butt or yours. Remember, Kittens, clothes should always fit you, not the other way around.
Well, since pretty much every pants pattern ever (or at least the two dozen or so I looked at) are drafted so the front and back crotch curves level, you’re going to have to alter them. Even if you made the pattern by duct-taping yourself, you may still need to do this, if you saw wrinkles similar to mine.
I just started by scooping out the bottom of my back crotch curve. The purple line at on the drawing below shows you roughly where to scoop, but you’ll have to experiment to find exactly where and how much on yourself.
I started out by scooping out only a very small amount (around ¼ in), tried on the muslin, had Felix take a photo, looked at the result, and kept on scooping more — until, magically, the wrinkles disappeared!
A happy ending
Note: I will be mostly showing the rear view in the following photos, since the front of all of these pants looked fine. I made them all in the same fabric so we’d be comparing apples to apples. You can ignore any various pocket and hem finish details, since they don’t affect the fit at all; I just wanted to make all of these wearable, so I could donate them to charity when I was finished.
So, in summary, we started out with a pair of pants, based on a pattern custom-drafted to my measurements following a standard pattern-making formula.
The first pants based on my duct tape shell had a seam down the middle back leg, and looked somewhat better, though far from perfect. Problematically, however, they didn’t have enough ease for me to move comfortably.
Next was the pair made from my revised pattern, now with more ease and a one-piece back. Again, worlds better than my original pants, but still not perfect. This was when the front and back crotch curves were still level with one another.
And finally, FINALLY, here are the pants I made after I finished scooping out my back crotch to make it significantly lower than the front (by nearly an inch, in my case, which is a lot in pattern-making terms).
The perfect pants, and where to go from here
Now that I’m in the elite club for people whose pants fit, what am I going to do?
For one thing, I need to go through my entire wardrobe, and replace every single pair of pants I own. Not just because the new ones will look so much better (though they will!). But because they will be so, so, SO much more comfortable and practical. Here’s why.
As it turns out, the same body features that caused those wrinkles, my “low buttocks,” were also forcing me to yank up my pants about a hundred times throughout the day.
Basically, the wrinkles were symptoms telling me that there wasn’t enough negative space in the bottom back crotch area. Meaning my bum was constantly “stealing” fabric from higher up to create enough space for itself lower down, making my back waistband pull down.
Once I “scooped out” enough space, the problem went away — and now pants waistband pretty much stays where I put it, even when I bend over. I had no idea how annoying it was to have to constantly hike up my pants, until I didn’t have to anymore. It actually changed my world.
What you can do with your new pants pattern
Your new pants pattern can be used for all sorts of additions to your future wardrobe, and not just for sewing this one pattern.
I hacked mine into overalls by adding a bib:
I’m planning on mashing it together with my perfected T-shirt pattern to make a knit jumpsuit, and widening the legs for pyjamas and summer palazzo pants. I’ll also be able to use it to alter any and all future pants patterns I make or buy by using its crotch curve as a reference.
I already made a pair of fully fleece-lined pants for freezing days, narrowing the legs a bit for extra wind exclusion. I wanted to see how this would turn out, because heavyweight pants are, well, heavier, meaning I’ve always had a huge problem with them falling down in the past. And like magic, these stayed up just fine! Here they are:
And that brings us to the long-delayed end of the pants-fitting saga.
If you don’t know, I decided to join the 21st century at last and learn how to use things like a laptop, email, and social media in February of this year. It was one heck of a learning curve, and I haven’t had time for much else since!
This may be the last blog here for a little while. Once I’ve dealt with the urgent business of creating an “online presence” (my new phrase of the year) for Felix & Kitty, my intention is to start a dedicated blogging site where I can write more useful posts – like step-by-step sew-alongs and hands-on tutorials for DIY projects.
Until then, thank you for those of you who are still hanging in with me, and hope to see you soon!
2 thoughts on “The Great Unicorn Pants Quest – Part 4”
I have the same low butt problem. When I scoop out enough to make a difference my back inseam is 1 1/2 inches lower than the front.
What is the best way to make them match? I have tried slashing ans spreading the back to add more below the crotch line but that makes the grain line almost touching the center back. Should I slash and remove from the front inseam? Should I adjust both front and back inseams?
In theory, when you scoop out the back crotch curve, it should not actually affect the inseam length at all. I am not sure what you’re describing regarding spreading the back — maybe you can email me some photos? You could also send me photos of your muslin fit and I can certainly give you my opinions on which alterations I think you might need to try next. Pants fit is so individual and tricky, and since I wrote this blog entry, I have found that sometimes, the direction of the grainline itself can cause very similar-looking bum wrinkles as the low butt issue. Generally, slashing and spreading along the crotch seam itself if rarely recommended, because it can create a host of other problems.