Seam allowance show-through

A shiny, flattened patch on fabric after ironing comes from too much heat and pressure crushing the fibers, common on wool and synthetics. Press with a pressing cloth and let steam, not pressure, do the work.

A zipper tape that ripples once pressed, though it lay flat while sewing, comes from ironing directly over the teeth and tape without support underneath. Press from the wrong side over a seam roll.

Corduroy or velvet that looks crushed after ironing comes from pressing directly on the pile with a flat iron sole. Press face-down on a towel or use a needle board so the pile can stand.

Interfacing lifting away from fabric in little bubbles after fusing comes from too little heat, pressure, or time, or sliding the iron instead of pressing straight down. Re-fuse with steam and firm, held pressure.

A brown or yellow mark burned into fabric comes from an iron too hot for the fiber, or leaving it in one spot too long. Test heat on a scrap first and keep the iron moving.