Directions:

In a saucepan, combine sugar, corn syrup, butter, cream of tartar and salt.
Boil rapidly on medium high heat, stirring constantly, until mixture reaches 260 degrees.  Remove from heat.  Stir in baking soda, mixing thoroughly.
Immediately pour over popped corn in a large bowl, stirring until well coated.
Place coated corn in a large buttered roasting pan. 
Bake caramel corn for one hour in a preheated 200-degree oven,
Stirring 3 or 4 times.
Store in a tightly covered container after cooling.
If it becomes sticky, place in oven again for a short while.