What Is Caster Sugar + How Do You Use It

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Caster sugar is surely an ingredient you came across while baking. If you got stumped about what this specialized sugar is, don't worry. You're not the only one who wondered what this kind of sugar could be. 

In the simplest terms, caster sugar is basically white sugar that has been ground more finely than granulated sugar but not too fine that it's been powdered. Caster sugar is also known as superfine sugar, baker's sugar, and has been spelled as "castor sugar" as well. 

White sugar is a kitchen staple.
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What makes this sugar perfect for baking? The superfine texture of this sugar ensures that with minimal stirring, it will dissolve faster than regular sugar granules. 

You may be wondering why you can't substitute powdered sugar with caster sugar since it is even finer ground than caster sugar. What prevents powdered sugar from being the perfect substitute for caster sugar is the fact that powdered sugar is so finely ground that it has a tendency to clump. To prevent this, cornstarch is usually added to absorb excess moisture. Sugar, after all, is a hygroscopic substance, or a substance that absorbs moisture from the air. 

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Cornstarch isn't always an ingredient that is favorable in baking recipes however. It can mess up the perfect ratio that makes a baking recipe work. 

So if you ever see caster sugar is an ingredient in your baking recipe, take a look at how it's used to see if it can be substituted with regular sugar. How can you tell? There are two instances where you can safely substitute caster sugar with regular sugar in baking: 

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1 Whisk egg whites to soft or stiff peaks. 

When it comes to whipping egg whites, caster sugar is best to help stabilize the egg whites so you can more effectively whisk it to soft peaks and up to stiff peaks without it clumping and looking overbeaten. Caster sugar is best but if you don't have it on hand, you can use regular sugar.


All you have to do is this: add regular sugar in earlier. Since regular sugar has larger granules than caster sugar, you will need more time to dissolve the granules. By adding it earlier, as soon as the egg whites are frothy, and waiting in between additions until each addition is somewhat dissolved before adding the next teaspoon or two. You'll get the same result at the end. 

Photo by Riell Santos

2 Roll baked goods in sugar. 

What makes caster sugar so great as a decorating sugar is its texture. The granules are perfect for a nicer mouthfeel with each bite. Regular sugar still has too large a texture that isn't the most pleasant. However, when you don't have caster sugar, regular sugar is a fine substitute for this. 

Did you know you could make superfine sugar with regular sugar? You can! Just like you can make powdered sugar, you can place regular sugar into a food processor or a blender and process it just enough that the granules are finer. 

Ready to start using caster sugar? Make a start of it by using it for whisking egg whites to stiff peaks and make the fluffiest chiffon cakes: 

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