I am trying out a new recipe and it says sifted cake flour. The cake flour I have has already been sifted and I thought all cake flours were pre-sifted. Does the recipe want me to sift this flour again before measure? I just want to make sure I get the right amount. But why would you have to sift cake flour a second time. I have never sifted my cake flours before... how do you do it?
all powders compact in transit (vibration) and sitting on the shelf (gravity)
so sifting aerates them -- loosens them up so you get better texture.
easiest way -- large wire mesh strainer -- as IndyDebi says "shake and bake"