Many people have noticed the small circular dent on the side of a plastic milk jug, but few stop to consider why it’s there. Even though it looks like a simple design detail, it actually serves an important purpose. Manufacturers include this indentation intentionally to help make the jug safer, stronger, and more reliable during everyday use. One of the main reasons for the dent is pressure control. Milk containers often experience temperature changes as they move from delivery trucks to store shelves and then into home refrigerators. When liquids warm or cool, they naturally expand or contract. The circular...
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