|Bias ruffles are made from a single layer of woven fabric...no hemming, not folded...the raw edge of the fabric is exposed. A true bias [cut at a 45 degree angle from the selvage edge of woven fabric] strip is gathered to form the ruffle.
See Marking and Cutting Long Bias Strips Tip
Also see Making Ruffles by Machine, No Special Foot Tip
I wanted to try this technique on a project, but hesitated to use it without knowing how it would look, after going through the washing machine and dryer. Test time!
I used a pale peach polyester satin, and sacrificed a triangle cut from the corner of the fabric, about 10" from the cut end. This gave me a 14" long strip of bias to play with. I practiced ruffling, using a tight upper tension on my machine [top section of photo link above].
I cut another bias strip from the triangle-shaped scrap of fabric, and gathered it close to one edge. Then I cut a straight-grain rectangle from the remainder of the scrap, to imitate a garment edge.
Next I attached the ruffle to the rectangle, RS together, with a zigzag stitch, which also finished the raw edge of the rectangle.
Last, I finger-pressed the ruffle down, and the seam allowances up [underneath the rectangle]. Then I topstitched to hold it in place [see second section in photo link above]. This is how I planned to sew it onto my garment, as a finish, instead of a hem.
Now for the laundry test. I realized my sample was so little, it could get lost in the washing machine or dryer. Normally, this would mean I'd put it in a mesh bag to launder it, but I wanted it to "take a beating", just like a full-sized garment would. So I hand-basted it to the hem of PJ pants that I was about to wash [third section in photo link above]. Tossed it in the wash, then in the dryer.
I'm happy to report that the raw edge of the bias ruffle came out looking very nice! It has a fuzzy or furry look to it, that I think is quite pretty [last section of photo link above has a close-up].
If a bias ruffle works this well in polyester satin [which has the wispiest of fibers woven together to make the fabric], it should work great with almost any woven fabric. But a test like this will let you know how each woven fabric will look, when used for a bias ruffle.
2-14 Edited to add a link to the Pattern Review for Satin Pajamas w/Bias Ruffles
Photo of the Ruffled Satin Pajamas