My latest project involves making piping for some bags. I found cotton 1/4" filler cord in the upholstery department as shown in the photo below. The sales clerk rolled it up loosely and placed in a shopping bag, as normal. However, when I got home and unrolled it, the cord had developed bulges here and there--it was no longer uniform as it had appeared on the spool. Cotton filler shown on right in the photo.
Determined to produce a better end result, I started hunting for alternatives for the filler and found a 3/16" diameter nylon braided rope in the marine department at the local big box store.
The rope is washable, uniform the length of the rope, flexible, and stable. I also had less problem with twisting of fabric. (See photo below). Cotton filler cord piping is on the left below, nylon on the right.
I used 1 1/4" wide strips of bias cut (on 45 degree angle) fabric strips to make the piping.
Moral of the story--use your imagination and consider alternatives for your creative work. Poke around the craft section and even the hardware section of department stores--you never know when you might spot something that you can work into a project!