But what is all this useful for? Actually, hygroscopic materials are all around you. Some common ones include wood, clay and wool. Because hygroscopic substances do such a good job of absorbing water they are often used as drying agents or desiccants, like the little silica gel packages. Those are helpful when you want to keep a product very dry. To determine how hygroscopic a material is, scientists measure how much water it absorbs, depending on the relative humidity of the environment. And now you can test some of these impressive materials right at home. Let's get started and explore what substances in your kitchen can absorb water from their surroundings.