Please help me im stuck on this question

Starch turns a blue-black color in the presence of iodine. julian decides to use this information to test the permeability of some dialysis tubing. julian fills the tubing with a starch solution and places it in a beaker of iodine and water. after two hours, the starch solution in the dialysis tubing turns blue-black. the iodine solution remains the same color (it doesn't change colors). what do julian's results show about the permeability of the tubing?