Kroc cooked his first batch, carefully duplicating the brothers' method. He peeled the potatoes, leaving a bit of skin for flavour, then cut Idaho shoestring strips and soaked them in cold water. After the water was white with starch he rinsed off the potatoes and then fried them in fresh oil. Out of the grease the batch looked just right, golden brown. But something was amiss. The McDonald's fries were always crispy, but this batch was mushy. Kroc struggled to reproduce the perfect fries. After several phone calls to California he learned that the McDonald brothers stored their potatoes in bins where they naturally cured in the dry desert air. Kroc put an electric fan in the basement of his Illinois store, blowing on the potatoes to produce the desert drying effect. After three months of trying he achieved the correct formula.