Tea Stains: Precipitated Beauty or Deadly Poison?
Leftover tea is most prone to forming stains
Scientific research shows that drinking water contains minerals and trace amounts of harmful heavy metal ions, such as cadmium, mercury, and arsenic. When water is heated, as the temperature rises, the solubility of certain calcium and magnesium ions decreases, and the concentration of insoluble salts increases continuously, precipitating out when the water is concentrated to a certain degree. These precipitates can enter the teacup when water is poured for tea. Tea that is not fully consumed or left exposed to air for a long time allows the tea polyphenols to oxidize with metal elements in the tea rust, producing brown tea stains, commonly known as tea scale, which adheres to the inner wall of the cup. Tea stains thus contain harmful metals such as cadmium, lead, mercury, and arsenic, and are the primary culprit endangering human health.
Long-term use of cups stained with tea scale can cause cancer
Associate Professor Li Hongzhu of the Tianjin Institute of Pharmaceutical Research once stated in an interview: "Tea stains contain toxic substances such as cadmium, lead, mercury, and arsenic, as well as carcinogens like nitrites. These substances adhere to the smooth surface of the teacup. When they enter the body through drinking tea and enter the digestive system, they combine with proteins, fatty acids, and vitamins in food to form insoluble precipitates. This not only hinders the body's absorption and digestion of these nutrients but also damages organs such as the stomach and intestines. Additionally, teacups that are not cleaned regularly retain more scale, which also contains large amounts of heavy metals, extremely harmful to health." Furthermore, these oxides entering the body can cause lesions and functional disorders in the nervous, digestive, urinary, and hematopoietic systems, and even lead to premature aging. In particular, arsenic and cadmium are carcinogenic, can cause fetal malformations, and endanger health.
How to thoroughly remove tea stains
The thicker the tea stains, the harder they are to clean, so daily cleaning and periodic deep cleaning are equally important. Experts recommend that after each use, even if no obvious tea stains are visible, the teacup should be carefully washed to prevent buildup over time.
(1) For stubborn tea stains that have accumulated over a long time, soak the cup in heated rice vinegar or a baking soda solution for a full day and night, then scrub with a toothbrush for easy removal. Note: If you are using a purple clay (Yixing) teapot, this method is not recommended. Purple clay has pores that absorb minerals from tea stains, which can help maintain the pot and prevent harmful substances from leaching into the tea and being absorbed by the body.
(2) Add a small spoonful of orange powder or orange juice (or other fruit juice) to the teacup or teapot, fill with clean water, and let sit for 2-3 hours. This will weaken the adhesion between the tea stains and the tea set, making them easier to remove.
(3) Add water and potato peels to the teapot or teacup, boil, then let cool. Rinse afterward, and the stains will clean off easily.
(4) For metal tea filters that have turned black from tea stains, if neutral cleaners are ineffective, soak them in vinegar or bleach to easily remove the stains.
(5) Apply table salt to the inner surface, especially where tea stains are present, then scrub vigorously with a toothbrush. Finally, rinse thoroughly with clean water.
Experts specifically remind that when removing tea stains, it is best not to use steel wool or rough cleaning balls, as these abrasive tools can damage the glaze on the inner wall of the tea set, making it thinner over time. Future tea stains will then penetrate deeply into the tea set, becoming extremely difficult to remove completely. It is advisable to use soft-bristled brushes, toothbrushes, or gentle cleaning cloths for cleaning.