When you put hot water in the "Air Pump Jug" or "Handy Jug" and later pour it into the cup to drink it, you may find something glittering like silver powder or glass powder in it. Sometimes it looks a shiny gold color. It's called "Flakes." Minerals in the water combine and make a thin film at the surface of the inner pot, then it breaks loose and floats in the water. These flakes are harmless to the health. It is in fact the result of calcium, aluminium, iron etc., being adsorbed by hydrous magnesium silicate (formed by the combination of the magnesium contained in the water with silicic acid) and forming a thin film on the surface of the glass, which then breaks down into small particles.
Flakes are not harmful
The flakes are composed of minerals such as silicic acid, magnesium and calcium that are already dissolved in drinking water, so they are not harmful to the human body. So there is no need to worry if you drink."
What to do when flakes occur
Once flakes have formed, the remaining deposit often sticks to the surface of the inner pot and is difficult to remove in many cases, and little by little, with each use, this will appear as flakes. If it occurs, dilute 10% citric acid with warm water and put in the pot, then leave it there from 30 minutes to 1 hour. Then wash it out with a soft brush inside the pot. Particularly in case of "water scale", wash the pot’s mouth or spout thoroughly.
The main cause of the occurrence of the flakes lies in water quality.
As mentioned above, the presence of magnesium and silicic acid are the required conditions for flakes to be produced, and it is also essential that the water is alkaline in order for these components to combine. Generally, water has carbon dioxide gas dissolved in it, so it tends to be acidic, with a pH of between 5 and 7; however, when boiled, the pH increases (becomes alkaline) and may even exceed a pH of 9. Moreover, magnesium is usually found in tap water, but it is not a component of the glass used for "Air Pump Jug" or "Handy Jug". Thus, the main cause of the occurrence of the flakes is the quality of the water, and depending on the degree of alkalinity after boiling, as well as the level of magnesium content, the magnesium may combine with the silicic acid (stone, sand, crystal, etc.) component of the glass of the "Air Pump Jug" or "Handy Jug", or with silicic acid contained in water, resulting in the occurrence of flakes." "In addition, the formation of flakes is also related to temperature, and the higher the temperature, the more likely they are to occur. In other words, "Air Pump Jug" or "Handy Jug", with their high thermal insulation, make it easier for flakes to occur. The flakes are slowly compounded in the "Air Pump Jug" or "Handy Jug", becoming crystals, then glittering flakes, by precipitation; however, if the right conditions are not met, crystallization will not occur, and the inside of the vacuum flask becomes stained with a fine precipitate (so-called water scale) which is formed by the precipitation of calcium etc. in the water.