Experts and BHG readers answer.
Why did my fudge get hard and turn grainy when I started to beat it?
The sugar in fudge is responsible for its texture. As sugar cooks and cools, it physically changes, forming crystals, some tiny, some big. Graininess results when sugar crystals get large. To keep this from happening, wash down the sides of the pan with water as the fudge cooks using a pastry brush. Follow the timings and temperatures as given in the recipe.