Recipe for the Iodine Solution:
Always make up a fresh iodine solution. Keep this solution in a dark-colored (or foil-wrapped) bottle and away from light. Since iodine is poisonous, treated apples should also be considered poisonous and should not be eaten by people or animals or used in composting. Do not allow pets to lick the fruit after testing.
Dissolve 10 grams (about 1/3 ounce) of potassium iodide in 10 ml (approximately 1/8 cup) of water. When it is dissolved, add 2.5 grams (about 1/12 ounce) of iodine crystals. Shake the mixture until the crystals are thoroughly dissolved. Dilute this mixture with water to make 1.14 liters (1 quart).
Make sure the solution is completely mixed by shaking the bottle every day for several days.