From a safety point of view, glass may be the best choice. No harmful substances seep out basically, and water can be injected at different temperatures. But glass still has its shortcoming, that is, it is fragile.
glass
2 stainless steel cups
Food-grade stainless steel cups are immersed in quite strong acid for a long time in standard tests, and metals such as chromium and manganese can be neglected. However, we usually only use it to hold water, tea, coffee, juice and so on. It is much milder than the test conditions, so there is no need to worry about the leakage of harmful metals.
Stainless steel cup
3 ceramic cup
Under-glaze colored ceramic cups, that is, the ceramics are colored first, then fired at high temperature, and finally the pigments are covered with glaze, so that the heavy metals in the pigments are difficult to precipitate, which is relatively safe. On the contrary, heavy metals in pigments will easily seep out when glazing. It is healthy to choose ceramic cups without pigment patterns.
ceramic cup
4 enamel cup
Because of the low calcination temperature, the porcelain formed by enamel cups is not stable enough. When the enamel cup comes into contact with food (especially acidic food), harmful metals will seep out. Moreover, after the porcelain on the surface is damaged, the metal hidden under the porcelain is more likely to seep out. So this kind of cup is not recommended.