Hey y’all! Heather here. Today I want to share a tutorial for adding an invisible zipper to our Pietra Pants. I love this pattern because it’s the best of both worlds, pants-wise; a clean, flat front and a gathered elastic waist at the back for comfort. In order to make them easy to get on and off, we built a lot of elastic gathered ease in the back. As a result, the back is gathered a bit more than a pair of pants that have elastic gathering all the way around. The downside of this is that it makes grading between more than two sizes a bit of a challenge, since you need to add even more gathers/ease to the waist in order to get them over your hips.
For this reason, we suggest adding an invisible zipper so you don’t have to add a lot of fabric bulk at the waist in order to get them on and off. It’s also a good option if you’d like to sew them out of a heavier fabric; a more structured fabric will create more pronounced gathers, so eliminating a bit of waist ease will create a more flattering effect in the back.
I wanted to make a pair of cool weather Pietras out of a durable cotton canvas (which happen to create a pretty awesome workwear-inspired “suit” with the new jacket pattern we’re launching next week!) I’ve been sewing a lot with canvas lately – I love how it looks in garments, and it weathers and ages beautifully. Here are the pants I made:
I suspected that such a firm fabric would look better with less ease/gathers in the back, so I decided to remove a bit of width through the top of the back waist, like so:
If memory serves I took an inch or so from the top of the back leg, grading to nothing at the hip. This removes about 2″ total gathering ease from the waist, keeping the comfort of that elastic but reducing the amount of gathering overall. You can do this regardless of whether or not you’re grading between sizes – it really depends on how much gathering you’re after. Once I had my modified pattern, I set about inserting an invisible zipper – let me show you how to do that!
First off, you want to get your pants mostly assembled. You should attach the front facing to the waist seam, and attach the back waistband. One side seam should be completely sewn, and the other should be sewn till about 7″ from the top of the waist (or however long your invisible zpper is). Your elastic should be sewn to the side seam on the side you are not installing the invisible zipper. Your pants should look something like this:
Notice that on the right side of the pants where I’m inserting the zipper (as I would be wearing them) the waistband and facing are still free. In the above image I had actually basted the entire side seam closed to try them on, but that seam should be free so you can insert the zipper. The biggest difference in construction here is that the non-zipper seam will be serged or finished together and pressed to the back. The zipper side seams should be finished separately and pressed open.
Once you’ve got to this stage, lay your zipper on the side seam and mark where the zipper teeth end:
Pin the zipper to the back leg, making sure you don’t capture the top half of the waistband in your stitching. The top of the zipper teeth should end at the fold you pressed in your waistband.
Sew the zipper in place using your invisible zipper foot as far down as possible. Repeat for the other side, ensuring the top of the zipper teeth aligns with the top of the waistband. Do the zipper up to ensure everything meets up nicely. If you need more guidance sewing an invisible zip, we have a tutorial here.
Before we can enclose the zipper with our waistband and facing, we have to finish inserting the elastic. It’s the same process as in the instructions, but we’ll keep the end of the elastic free for now so we can try them on later to test the fit.
Fold the waistband over the elastic and pin into place, ensuring about 1/8″ extends past the waistband seam so you’ll have fabric to catch when you stitch in the ditch in the next step.
Make sure you leave at least 3″ free on the zipper side so you can flip the waistband over later on. Stitch in the ditch to mostly close the waistband.
At this stage, I suggest trying your pants on to finalize the length of that elastic. Make sure the pants fit snugly (but not too tight!) before sewing the elastic in place on the zipper seam, next to the zipper teeth.
Once the elastic is secure, flip the inside of the waistband over to encase the other side and the elastic. Fold the top edge of the zipper tape down so it’s in line with the waist seam.
Stitch in place, being careful not to sew over your zipper teeth. Here’s what it looks like on each side:
Clip the corner and flip the waistband right side out. The zipper teeth should be sandwiched between the back and the waistband.
Finish stitching in the ditch to enclose the elastic.
Next, its time to enclose the other side of the zipper between the front leg and facing. Fold the top edge of the zipper tape down so it’s tucked out of the way.
Flip facing down alongside seam and pin in place.
Sew facing to front leg, again careful you’re sewing next to the zipper teeth and not catching them in your stitching. Clip corners and turn right side out. Ensure the zipper does up evenly and finish waistband by topstitching elastic in place.
Here is what it will look like from the right side. My fabric was quite thick so it was tricky to get a perfect corner on the front but it looks very clean!
I also chose to add a little line of stitching to the bottom pocket edge since there are quite a few layers here and I wanted to anchor everything together.
Needless to say, I love these pants! I’d like to make another pair in dark denim, perhaps a bit longer to keep my ankles warm when the snow descends.
Now go forth and add a zip to your Pietras! You won’t regret it.