Air pop the pop corn, keep it plain. No butter or Salt just plain. Gently pick out un-popped kernels. Place into a basting pan (like the one you use for turkey). You can also use a strong tin foil basting pan that is recyclable.
Preheat the oven to 250 degrees. Combine salt, sugar, butter, Karo light corn syrup in a sauce pan. bring to a boil for five minutes stirring constantly. Take off the heat and add the vanilla and the baking soda. Stir until mixed. Pour over popped pop corn and gently fold in.
Placed into oven uncovered for fifteen minutes at 250 degrees. Take out and gently fold over itself trying not to break up the popped popcorn. Place back into the over for another fifteen minutes. Repeat for a total of four fifteen minutes, totaling an hour. You are drying out the pop corn for a light and krispy treat.