Powdered sugar has the smallest crystal size of any of the white sugars, as small as 0.01 millimeters. It’s also known as “confectioner’s” or “icing” sugar depending on where you live. The tiny crystals make it good for dusting and of course making frostings and icings. The only major drawback to powdered sugar is its flavor and texture which can be chalky. The reason, because powdered sugar contains up to about 3% corn starch, which is there to absorb moisture and keep the tiny crystals from clumping.