I have a few shirts that are 100% cotton and billed as wrinkle-resistant (and they really are). What I can’t figure out is how the creases are permanent.
How do they get the creases in? Conventional ironing won’t do this.
Are they definitely 100% cotton? In my experience most crease-resistant shirts contain a small amount of polyester in the fabric. I always assumed that the creases were put in with a device hot enough to slightly melt the polyester into shape, but I could be wide of the mark with that one…
Just heat and pressure. Probably the pressure is the real key, since when you overheat at home you (that is I) get scorch marks.