They’re both sugars, and you can make one out of the other. But the difference between granulated sugar and powdered sugar is the cornstarch. Yes, cornstarch is added to powdered sugar to keep it dry and to eliminate the possibility of chunks forming. If you keep your granulated sugar in the refrigerator (a humid climate), you may have noticed clumps in it. That’s what would happen to confectioners’ sugar if there were no cornstarch. OK, now that we’ve got that straight, let’s get to the question: “Can I replace granulated sugar with powdered sugar?” In a word (or a few) ‒ no ‒ and yes, kind of.
Types of Sugars
If you’re one of the many home cooks who is getting into baking, having perhaps been watching those marvelous televised baking shows, you may be encouraged to try recipes you’d never thought of before. Cakes, cookies, pies, doughs ‒ all call for sugar. But, looking on the grocery shelf, we’re faced with a host of choices. In America, we’re used to granulated sugar called just that, granulated sugar. But it’s also known as table sugar, refined sugar or just plain white sugar.
But fine baking calls for fine ground sugar, and some American manufacturers now sell fine granulated sugar. In the UK, fine ground sugar is known as “caster sugar.” Be careful when substituting one for the other: Caster sugar dissolves much more quickly than granulated sugar, and it should be reserved for mixing with liquids.
Powdered sugar also has its own identity crisis. Icing sug_ar, _confectioners’ suga_r ‒ all are terms for _powdered sugar. You may even see a package with “10X” on the label, which specifies how finely ground it is.
Consider this scenario: The recipe you want to make calls for 1 cup of granulated sugar, and you don’t have any, but a bag of powdered sugar that’s been on your shelf for ages stares back at you. The ratio for substituting one for the other is 1 3/4 cup of well-packed powdered to 1 cup of granulated. Simple? Not really. Because what the ratio doesn’t take into consideration is if the recipe calls for cooking or baking, and it does make a difference.
Cookie dough with powdered sugar won’t bring the same result as granulated sugar. Your cookies will be drier. The opposite problem occurs when you try to substitute granulated sugar for powdered in an icing or glaze – that results in a grainy mixture. You won’t find a recipe for buttercream frosting that calls for granulated sugar because you’ll taste those grains of sugar instead of the smooth blend of butter, powdered sugar and vanilla.
However, if you’re making whipped cream and want a heavenly, puffy cloud, sift powdered sugar into the mixer as it whirls instead of granulated sugar. Your whipped cream won’t be weighed down by the sugar, and a lofty cream is the result.
When NOT to Substitute
Sweet sauces will thicken if you use powdered sugar instead of granulated. The cornstarch already added to confectioners’ sugar when you buy it is a thickening agent; however, liquids mix best with fine granulated sugar. If you don’t have a choice and must use powdered sugar, first make a slurry by whisking the liquid with powdered sugar until it’s well-blended, and then add it to your recipe.
My seventh grade English teacher didn't realize what she was unleashing when she called me her "writer," but the word crept into my brain. I DID become a writer. Of advertising copy, dialogue and long-term story for several network soap operas, magazine articles and high-calorie contents for the cookbook: Cooking: It AIn't Rocket Science, a bestseller on Amazon! When I'm not writing, I'm cooking!