A dramatic visualization showing how 1/8 teaspoon of sugar spreads depending on degree of granulation.
Superfine sugar, aka “baker’s sugar,” is the finest granulation before becoming powdered sugar. It is called for in recipes such as meringue, because it will dissolve more easily into the egg white, in cookies when a smooth dough and exterior is desired, and in butter cakes for the finest texture.
You can make superfine sugar by processing fine granulated sugar for several minutes, but if processing large quantities it will scratch the food processor bowl and make it a bit cloudy. Also, some bakers feel that the granules will be less consistently even but personally I have found there to be no noticeable difference in the finished product.
Different brands of superfine sugar will vary in degree of fineness. I used Domino brand for years and then found that C & H was slightly finer. But the finest of them all is the India Tree brand.
Note: All sugar will lump on storage, and the finer the sugar, the more prone it is to lumping. Powdered sugar, for example, contains a small amount of cornstarch to help reduce its tendency to clump. With refined sugar, all you need to do is press it through a strainer to restore its free-flowing consistency.
Here is the link to India Tree for their sugar:
If you would like to read more on sugar, Rose wrote a Sugar Bible article for Food Arts. Here is the link: