|The manual that came with my sewing machine is pretty detailed, but it doesn't have much about the tension adjustments. Over decades of sewing, I've figured out a lot just by trial and error. It occurred to me that I should be able to ruffle fabric, just by adjusting the top tension.
So I tightened the upper tension on my sewing machine, as tight as it would go...my tension dial is numbered 0-11...I had it at 11. It's normally set at 3, for most of my sewing.
Then I stitched through a strip of fabric with a long stitch [6 stitches per inch, or 4mm length]. This gathered the fabric without the use of a special ruffler foot, at a 2:1 ratio. I liked the way it looked, the gathers were evenly distributed, and 2:1 is an attractive ruffle proportion.
Curious about whether this technique would only gather a single layer, or if it would work on a double layer of fabric, I tested that too...also works great [see photo link above].
Since a long stitch is used, the gathers can still be adjusted if necessary. Also, handle the ruffle carefully until it's sewn to your project, as the gathers can move or come out.
Tip...as you run the strip of fabric through your machine to gather it, don't let the ruffle hang down behind the machine. The weight of the fabric pulling down could lessen the amount of gathering.
2-14 Edited to add a link to the Pattern Review for Satin Pajamas w/Bias Ruffles
Photo of the Ruffled Satin Pajamas