Wikipedia Article About Superfine sugar on Wikipedia Superfine sugar, favored for sweetening drinks or preparing meringue. Caster sugar is the name of a very fine sugar in Britain, so named because the grains are small enough to fit though a sugar "caster" or sprinkler. It is sold as "superfine" sugar in the United States. If you don’t have any caster sugar on hand, you can make your own by grinding granulated sugar for a couple of minutes in a food processor (this also produces sugar dust, so let it settle for a few moments before opening the food processor).