oChef » What Is Castor Sugar and How to Use It

What Is Castor Sugar and How to Use It

Castor sugar, often spelled caster sugar, is a type of very fine white sugar commonly used in British baking. In the United States, you will typically find it sold under the name \"superfine\" sugar. Its texture sits somewhere between standard granulated sugar and powdery confectioners' sugar.

Because the grains are so small, castor sugar dissolves much faster than regular sugar. This makes it a preferred ingredient for delicate baked goods like meringues or for sweetening cold beverages where grainy texture is unwanted.

Understanding the Texture and Name

The name “castor” comes from the sugar’s ability to fit through the holes of a sugar caster, which is a type of table sprinkler or shaker. While standard granulated sugar grains are often too large for these shakers, castor sugar flows through easily.

It is distinct from confectioners’ sugar (also known as powdered or icing sugar). Confectioners’ sugar is crushed mechanically into a fine dust and generally contains a small amount of cornstarch to prevent clumping. Castor sugar, by contrast, is simply pure sugar ground to a finer crystal size without added starch.

Common Uses in the Kitchen

The primary advantage of castor sugar is its ability to dissolve quickly and integrate seamlessly into mixtures.

Meringues: Since it dissolves rapidly, it helps create a smooth, stable foam without the risk of grainy sugar crystals remaining in the egg whites.
Cold Liquids: It is excellent for sweetening iced tea, cocktails, or cold desserts because it does not require heat to dissolve fully.
Lighter Baking: In sponge cakes and cookies, the finer crystals can incorporate more air during the creaming process, potentially leading to a lighter texture.

How to Make a DIY Substitute

If a recipe calls for castor or superfine sugar and you only have regular granulated sugar, you can make a simple substitute at home.

Place standard granulated sugar into a food processor or clean coffee grinder.
Pulse or grind the sugar for a couple of minutes until the grains are significantly smaller.
Let the dust settle inside the bowl for a few moments before opening the lid to avoid inhaling the fine sugar cloud.

Quick tip: Be careful not to over-process the sugar, or it may begin to turn into powder similar to confectioners’ sugar.

FAQ

Is castor sugar the same as powdered sugar?

No. Powdered sugar (confectioners’ sugar) is ground into a fine dust and mixed with starch to prevent clumping. Castor sugar is made of distinct, tiny crystals and usually contains no starch.

Can I use regular sugar instead of castor sugar?

In many recipes, yes, but the texture may be slightly grainier. For meringues or cold drinks, regular sugar might not dissolve completely, affecting the final quality.

What is the American equivalent of castor sugar?

In the United States, castor sugar is sold as “superfine” sugar. It is the same product, just labeled differently.