I've found that organza
is the best fabric to use to achieve this really ruffly effect. I cut out my circles, then use my scissors to make "divets" around the edges of the fabric (scalloped edges). As mentioned above, slowly lower the fabric to the candle, but don't let the flame get too close to the fabric, as organza curls and heats up VERY QUICKLY! (learned this the hard way). I also have found that it curls up (ruffles) better for me if I focus singing toward the center of the fabric rather than the very edges. It gives the fabric layer more of a "cupped" appearance.