The terms 'hard' and 'soft' water refer to the mineral content found in the water. Hard water contains high levels of dissolved minerals, primarily calcium and magnesium, which it picks up as it flows through limestone or chalk deposits. Soft water, by contrast, has low mineral concentrations. In the world of beverages, water hardness is vital. For example, the soft water of Pilsen in the Czech Republic is perfect for making crisp Pilsner lagers, while the hard, mineral-rich water of Burton-on-Trent in England is ideal for brewing bitter Pale Ales, as the minerals highlight the hop bitterness. Similarly, tea enthusiasts often prefer soft water because the minerals in hard water can react with tea polyphenols, creating an oily film (scum) on the surface of the tea.