When making icing sugar from raw sugar for glace icing I notice it goes a murky brown colour, is this usual?
You use pure icing sugar when you want the icing to go hard. Soft icing sugar has tapioca added to make it stay soft ( for example when you decorate cup cakes or a butter cake)If a recipe says icing sugar, I use soft icing sugar. I only use the pure when I'm making fondant or decorations to adorn the top or sides of cakes.