Silver Spoon / Tate & Lyle Caster Sugar is predominantly used for baking and creating lighter cakes. Caster Sugar is made of extremely fine sugar crystals which incorporate more air than other sugars; this is why it is so light and fluffy. This quality icing sugar is just what you need for creating lighter, fluffier cakes. It is also just the ticket for whipping up a soft and airy meringue.