Once sugar has been refined, it is passed through sieves with a specific hole size that determines the largest grain in any given batch. Some sugars are also sieved to remove smaller crystals. All refined sugar has equal sweetening power (by weight), regardless of the degree of granulation. The one exception is confectioner’s sugar, because it contains a modicum of starch.
Loaf or cube sugar is granulated sugar that has been pressed into molds while still moist. It is subsequently dried to retain its shape. Most sugar was sold in this form prior to the late nineteenth century; consequently, old recipes sometimes call for it. See sugar cubes.