What's that rainbow film on your tea? It's not what you think!
Occasionally, you might notice a delicate film on the surface of tea that shimmers like a rainbow. It's natural to wonder about the colors appearing in your cup. Where do they come from, and what do they mean?
Foam and the film on tea are phenomena that often raise concerns. However, their causes are typically simple and not worrisome. While they may look unusual, there's nothing harmful about them. It's helpful to know where they originate, and there are ways to prevent them. This is a fun fact you can share with your mother-in-law during afternoon tea.
Where does the rainbow film on tea come from?
The film that appears on the surface of tea is different from the film seen in milk, with its sheen resembling spilled gasoline. It results from the interaction of tea polyphenols with calcium carbonate in the water (especially in hard water).
The harder the water, the more visible the film will be on the tea. You can avoid this by filtering the water before brewing the tea. Adding a slice of lemon can also help reduce the risk of this film forming. While the film may look unsightly, it is not harmful to health and does not significantly affect the flavor of the brew.
Foam in tea
In addition to the rainbow film, foam may also appear on tea. There are several reasons for this, one being saponins. These are natural chemical compounds found in tea leaves that create foam. Saponins are harmless to our bodies, and the foam they create is not a cause for concern.
The way tea is poured also impacts foaming. If tea is poured with a strong stream from a height, more air is introduced into the drink, which escapes during brewing in the form of foam. Sometimes, this is even desirable, such as in Moroccan tea, where it is deliberately poured from a great height.
The type of tea leaves also contributes to foam formation. Small, loose leaves contain more air, which "escapes" when the tea is poured with boiling water, resulting in foam. This remains a harmless phenomenon that does not affect the taste or properties of the drink.
