aka the grittiness you feel in the fudge. Instead, wait to pick up the spoon (our Test Kitchen loves using wooden spoons) until the fudge drops to between 110 and 113°F, about 15 minutes.
The refrigerator will cause the fudge to dry out and pick up the scents and flavors of food near it. The last thing you want is for your famous fudge to start tasting like cucumbers or other veggies.