Sugar to Confectioner's Sugar

[MayFox]

I've recently been doing some research into how to make homemade frosting/icing, because it is cheaper, and even a bit less sugar than store bought. I don't have Confection Sugar, but I did find a way to make it myself, but in every thing I see that you need Cornstarch, but in a few it say that it's optional. Is Cornstarch needed and why?

 

[SatNavSaysStraightOn]

Cornstarch is there to get it to flow correctly and not clump together because sugar flour which is in essence what you are creating, is a hydrophillic substance, so likes to absorb water. Cornstarch also helps to somehow prevent this, I'm not certain why.

If you were to make up what you needed and use it immediately, you would not need to add cornstarch to it.