Why does the zipper warp after ironing a jacket?

Q: Why does the zipper warp after ironing a jacket? Ironing warps a zipper when heat passes through the tape into moulded teeth, or when the tape is stretched while hot. The pattern of the warp shows which happened, and both are corrected at the iron rather than at the zipper. Check whether the warp follows the iron path or sits at the slider rest position. Confirm whether the iron touched the teeth directly or only the fabric beside them. Measure tape length before and after ironing a scrap to detect stretching. Review the iron temperature setting against the zipper care guidance. Iron a scrap at a lower setting with a pressing cloth and compare. Warp along the iron path points to heat, and warp at the slider points to pressure on the chain. Give operators a simple rule: press around the zipper, not across it, and keep the iron below the tape's comfort range. A pressing cloth is the cheapest control and prevents most of these claims.