Here's a blog post that I originally wrote for The Daily Stitch, the Village Haberdashery's blog. Once again, they have been very kind and allowed me to re-post it here for those that didn't see it first time round. BTW, you can find the VH's range of zips/zippers here.
The ability to shorten a zip is a very useful skill to have in your sewing-bag of tricks. Often a student will arrive at a class I’m teaching all stressed out because they couldn’t find the exact length zip that a sewing pattern called for, in the right colour for their project. My advice is always this: focus on finding a zip that is a great colour match for your chosen fabric. If the zip is a couple of inches too small, it’ll still probably be fine for your project, and if it’s too big then it can easily be shortened. If you type in ‘How to shorten a zip/zipper’ into YouTube, you’ll find heaps of videos on the subject. However, here is the method that I prefer…
Please note: this tutorial is for shortening regular or invisible/concealed zips with nylon teeth, not metal ones.
Step 1: Find out how much shorter you want your zip to be.
Step 2: Place a pin where you want the new stopper to be. Alternatively, you could mark the zip tape with chalk or a marker pen.
Step 3: Put a strong needle in your sewing machine (I like to use a 90/14 needle for this process). Position the zip underneath your presser foot so that the needle is directly above the pin that you placed in the zip tape. Lower the presser foot so that the zip tape is clamped down and remove the pin.
Step 4: Slowly sew across the zip tape from one side to the other. It may feel a bit weird to do this, so use the hand wheel rather than the foot pedal if sewing over the zip teeth is freaking you out. But don’t worry, your needle is extremely unlikely to break!
Step 5: When you reach the other side of the zip tape, make sure the needle is piercing the zip tape (use the hand wheel if necessary). Then lift the presser foot, spin the zip round 180 degrees , lower the presser foot again and stitch back over the row of stitching. Do this three or four times to create a strong new zip stopper.
Step 6: Remove the zip from your sewing machine and snip away any loose threads.
Step 7: Measure ½” below your new zip stopper and cut the excess away.
Step 8: Most zip shortening tutorials stop at this point, but I like to seal the bottom of the zip tape to prevent it from fraying. Quickly pass the cut edge through the flame of a lighter. I’m sure this goes without saying, but please take care using a lighter!
Done! A freshly shortened zip to your exact specifications, that won’t fray in the wash!