One of the most useful items in the cake decorator's pantry is confection's sugar, also known as icing sugar, 10x sugar, or powdered sugar. Many desserts and treats would be overwhelmed by the application of decorative frosting and need only a dusting of this finely powdered sugar to make them look tempting. Confectioner's sugar is white, granulated sugar that has been ground by machine into a fine powder.
The powdery delight is a common ingredient in many cake icings, glazes, dessert sauces, and decorative frostings. Many times, confectioner's sugar is the finishing touch—sifted over donuts, beignets, and funnel cakes—to add just a bit of sweetness.
Confectioner's sugar is not meant to be used as a substitute for granulated sugar in most recipes. For one thing, powdered sugar costs a great deal more than granulated sugar which would make it a poor choice for budget-minded cooks. In addition to this economic consideration, confectioner's sugar is not heat-tolerant and is therefore inappropriate for use with prolonged high temperatures. The best use for this sugar is in icings and glazes and not in cakes, cooked sauces, or puddings. Besides these concerns, most confectioner's sugar is not pure granulated sugar but has had anti-caking agents added to it—in some cases a package will contain as much as 3% added cornstarch as an anti-caking agent.
The confectioner's sugar you'll find in your local grocery store has undergone the grinding process ten times which is why many packages of confectioner's sugar are marked "10x." This has become an alternate name for the ingredient. Different grades of confectioner's sugar are sometimes available. For instance, you might find 4x or 6x grind. This means that the sugar has been ground 4 or 6 times, respectively. The more times the sugar has been ground, the finer it is likely to be. You want a very fine sugar for making uncooked buttercream icing so you'll get a proper melding of the ingredients. Use a coarser grind and your icing will be gritty and may clog the smaller decorating tips. But the coarser grinds should be fine for sifting over cakes or cookies.
Some people will tell you that it is possible to make your own confectioner's sugar at home by grinding granulated sugar in a blender or food processor. However, experience shows that the homemade confectioner's sugar can never match the finely powdered texture of the commercial product. As you grind the sugar, it will superheat and clump, never getting as fine as you'd hoped. Homemade confectioner's sugar can be used for dusting baked goods and desserts, but not for making icings and glazes.
Store confectioner's sugar airtight and keep it safe from dampness and moisture. Stored the right way, the sugar will keep for an indefinite period, so you're safe in stocking up on large quantities of this pantry staple when it is on sale.