I gathered together the supplies needed. I used pure cane white sugar and corn starch. Apparently the cornstarch works as an anti-clumping agent, and arrowroot can be substituted. I had no arrowroot on hand so I can't speak to the efficacy of it's use. I set up my VitaMix blender. Just a tip; I have learned when I want to use mine for grinding dry ingredients, and want to prevent the spout from being caked full of the end product, I take a piece of paper towel or small piece of fabric, roll it tightly and place it in the spout, from the inside, leaving a very small amount sticking out into the container. Be VERY CAREFUL to pack tightly so that it does not slip out during blending. With the centrifugal force and outward pressure of the blending, there is minimal chance of it coming, but I am still careful to avoid it being loose. You may have to use tweezers to remove it, but this is much easier that trying to dig out the dry packed, product when you are cleaning up.
Add 1 Tablespoon cornstarch to the sugar. You may also choose to use arrowroot.
Pour the two ingredients into the blender. Place top on Blender. This is a very important step, as this process creates a lot of sugar dust. Not only will the be messy, but you don't want to breathe in these small particles. Keep the lid in place during the blending process and let the dust settle before opening the top. Do not blend for more than 30 or 45 seconds at a time to avoid heat production and melting the sugar.
The finished product is fine and fluffy with the same characteristics as the purchased confectioners sugar. This is used for icing, candy centers and other baked goods. The original 1 1/2 cups expands as it is ground into the find powder.
Filling the jar was a little messy, but it wipes right up with a wet cloth.