1. scrub with soft cloth or small towel with salt or detergent. If the bottom of the cup is not deep enough, you can wrap the scrub on the chopsticks or wrap it on the toothbrush. 2. toothpaste can be wiped. 3. break the egg shell, put it in a cup with hot or white vinegar, cover it and shake it to remove the tea scale. 4. and the skin that can be used with potatoes.
Scale: scale is due to the use of kettle for a long time, and a thick layer of impurities will grow on the inner wall. Just under the rain and snow, there is no mineral substance in the water, it is "soft water". After the water was boiled, some of the water evaporated. The calcium sulphate (CaSO4, gypsum), which was not well soluble, precipitated. The dissolved calcium bicarbonate (Ca (HCO3) 2) and hydrogen carbonate (Mg (HCO3) 2) decompose in boiling water, release carbon dioxide (CO2), and become dissolving calcium carbonate (CaCO3) and magnesium hydroxide (Mg (OH) 2), also precipitate, and sometimes produce MgCO3. So the scale is formed.