Domain: society (Home Maintenance and Lifestyle Crafts)
Problem: This is my first time sewing an invisible zipper and the final result looks terrible. People on forums suggested that the fabric was stretched, but that makes no sense to me because I am using a vintage 100% cotton fabric with a very tight weave. Why did the fabric grow longer and pucker after I sewed the zipper? What is the underlying physical principle for this? If I were to redo the project, what must I add to the fabric to completely prevent this from happening again?
Answer: The cause is "Bias Stretch." Use "Interfacing" on the seam allowance to stabilize the fabric.