The material of the thermos cup is basically stainless steel. Stainless steel contains metal elements that are relatively stable under normal conditions. However, in an acidic environment, some substances that will react with metals and are harmful to the body may be dissolved.

There is an acidic substance called tannic acid in coffee, which will cause slight damage to the thermos cup, greatly shorten the life of the thermos cup and make the thermal insulation performance worse and worse. It is also prone to chemical reactions, which will have an impact on health over time. Moreover, after long-term insulation and heating, coffee will destroy the taste and easily deteriorate.

In addition, coffee is easy to remain in the thermos cup and it is difficult to clean it. After a long time, dirt will form in the thermos cup, which is not only difficult to clean, but also harmful to the body.

Which cups can't make coffee?

1, enamel cup

Enamel cups are glazed at a high temperature of thousands of degrees Celsius and contain stable metal substances. If it is used to hold acidic drinks such as coffee for a long time, the metal substances on the enamel cup are easy to dissolve out. In addition, the surface of the enamel cup is easy to be damaged and the paint falls off. Some harmful metal substances may seep out.

2, stainless steel cups

Stainless steel cups are durable and corrosion resistant. But stainless steel cups are metal products, which contain heavy metals such as nickel, chromium and manganese. Like an enamel cup, if you don't pay attention to it, the heavy metals in the cup will seep out for a long time, which is harmful to your health.

3. Colored glazed ceramic cups

The pattern on the glazed ceramic cup is painted with pigment, and the inner wall is painted with colored glaze. When filling acidic coffee drinks, harmful heavy metal elements such as lead will be dissolved in the drinks, which is harmful to health.

4. Wooden cups

Cups made of wood and bamboo are environmentally friendly and harmless to human health, but if they are not cleaned, they will become moldy and black, especially when sugary drinks are put. If the wooden cup is used for a long time, it will crack if it is filled with overheated water.