There are a few baking recipes I want to try that call for Caster Sugar (a.k.a. - Super Fine Sugar, also seen spelled "Castor"). I understand why it is called for in a recipe. I've done a little research in an effort to find out if I can simply make Caster Sugar by grinding regular, white granulated sugar and it appears you can. It also seems that you can't substitute Confectioner's Sugar due to the difference in density and the added cornstarch.
I've made Confectioner's Sugar before but never Caster Sugar. How do you know how far to take the grinding process for Caster Sugar?
Are there any experienced bakers out there who make their own Caster Sugar who might have some tried and true instructions or tips on making it to consistently achieve the proper consistency and weight?
Thanks.