ASorry I can't seem to find a clear answer. Is castor sugar the same as extra fine granulated like you would use in IMBC?
Caster sugar is very fine and when I have a recipe that calls for it I just run a bunch through either the blender of food processor, pulsing quite a few times. Then I measure the amount.
In Australia we call it Castor Sugar - whilst other Countries call it Extra Fine ...but it is the same thing.
Yes, my grocery store sells extra fine sugar labeled as "Bakers Sugar" by C&H I think. It comes in a paper style milk carton. It's easy to pour out from the spout, then I can put a bulldog clip in the opening to seal it tight.
In Canada, it's also called "Berry Sugar", and the bag clarifies that by saying "extra fine granulated sugar". You can also buy Super Fine Sugar at Bulk Barn.
Before I figured that out what was what (thank you Google), I was whizzing sugar in my (clean) coffee grinder. Pain in the rear!
It's so darn confusing sometimes.