A foam layer on tea can be caused by several factors. Firstly, hard water, which is rich in minerals like calcium and magnesium, can react with antioxidants in tea, such as catechins, to form foam. Additionally, some types of tea contain natural saponins, soap-like substances that can lead to foam formation when mixed with water. The brewing method, such as the temperature of the water and the brewing time, can also affect the amount of foam. Finally, the way water is added to the tea, such as pouring from a great height or stirring, can introduce air into the tea causing foam formation. This foam is usually harmless and does not affect the quality of the tea. For more information and answers to other frequently asked questions, visit our FAQ page . Discover more tips, advice, and interesting articles about our products and related topics on our blog .