Because there are some fat-soluble substances such as fatty acids, carotene and some volatile aroma components in tea soup. This kind of leaching substance has a light specific gravity and floats on the surface of tea soup.

When the tea soup reaches a certain high temperature, there is a certain temperature difference between the top and bottom of the tea soup, resulting in steam. Because of the barrier of this layer of "oil", water vapor can't evaporate into the air immediately. When the shape of tea is constantly changing, it will sometimes look like fog and sometimes like oil, and it will appear under certain conditions.

Extended data

There are five main factors that affect the appearance of tea.

1, the more fat-soluble substances in tea soup, the more obvious the tea brewing effect.

2. The darker the soup color, the easier it is to contrast, and the easier it is to find tea.

3. When brewing, the higher the temperature of tea soup, the more substances are leached instantly, and it is easier to produce tea. If the temperature is low and the air pressure is low on the day of drinking tea, it is easier to produce tea. The other is the container problem. If the soup container is light-colored, it will be easy to see the tea, especially when using white porcelain utensils.

4. If there are many substances in the tea itself, there will be relatively many extracts in the tea soup, so the amount of substances contained is one of the decisive factors for the formation of tea.

5. The refraction of light is also an influencing factor. Some teas are very thick, and the heat is high. When water vapor comes up, it will refract with light, and there will be a fog like water vapor.