Hello Brenda,
Making your own powdered sugar at home is a wonderfully easy way to save money, and it gives you complete control over what goes into your ingredients.
To address your point about store-bought icing sugar, commercial brands typically add an anti-caking agent, usually around 3 percent cornstarch or tricalcium phosphate, to keep the sugar from absorbing moisture and clumping into hard lumps on store shelves. While these additives are generally safe, making it yourself ensures you know exactly what is in your pantry.
To make powdered sugar at home, you only need two basic items: standard granulated white sugar and a starch such as cornstarch, arrowroot powder, or tapioca starch. The recommended ratio is 1 cup of granulated sugar to 1 tablespoon of cornstarch. If you plan to use the powdered sugar immediately for a recipe, you can even skip the starch entirely. However, if you want to store it for future use or use it in a smooth icing, adding the starch is recommended because it prevents clumping and improves texture.
Here is the step-by-step method:
First, place 1 cup of granulated sugar and 1 tablespoon of cornstarch into a high-powered blender, food processor, or clean coffee or spice grinder. A high-speed blender works best to achieve that commercial-grade ultrafine texture.
Second, blend the mixture on high speed for about 30 to 60 seconds. You will see a fine cloud form inside the container as the sugar crystals break down into powder.
Third, turn off the machine and let the sugar dust settle for about 30 seconds before removing the lid so you do not inhale the fine powder or make a mess on your counter.
Fourth, check the consistency by rubbing a tiny bit between your fingertips. If it still feels gritty, blend for another 20 to 30 seconds. For delicate icings, you can pass the powder through a fine-mesh sifter.
Finally, store any extra homemade powdered sugar in an airtight container or glass jar in a cool, dry place. It will last indefinitely just like regular sugar.
I hope this helps you save some money while keeping your baking pure and simple. Let me know if you have any questions about tweaking the process!