Is mercury coated on the inside of the thermos flask?

Is mercury coated on the inside of the thermos? Why is the small protrusion at the bottom broken and cannot be kept warm?

The secret of the heat preservation of the thermos is mainly the double-layer glass inner liner.

Let’s take a look at how the double-layer glass inner liner is made.

The raw material of the glass bottle liner is made of high-temperature resistant soda-lime-silica hydrochloric acid glass. The raw material is fired into a glass fluid at high temperature, and then blown in a metal mold into a glass bottle with a wall thickness of 1 to 2 mm. A glass tube is welded to the bottom of the outer bottle. In the following process, this glass tail pipe is used to extract the air between the inner and outer layers and for silver plating.

After heating, use a knife to cut off the excess part of the inner refill mouth. The cut part can be returned to the oven and used again. The outer refill is cut into two parts, mainly for loading the inner refill into it. Put the inner refill into the outer refill and put the asbestos or spacers that leaves a gap between the inner and outer refill, and then re-fused the two parts of the outer refill through high temperature and cut the excess part of the outer refill. Fuse the mouth of the inner and outer refill.

Inject pure water from the tail pipe, clean the gap between the inner and outer refill, drain the water, and then inject the silver plating solution. A certain amount of compound solution is used as a reducing agent and poured into the gap through the tail pipe to carry out the silver mirror reaction. The silver ions are reduced and deposited on the surface of the glass interlayer to form a thin layer of mirror silver film.

The air between the inner and outer bottles is drawn from the glass tube to become a vacuum.

Heated to 300~400℃ to evaporate the moisture in the interlayer. melt-sealed the glass tube at the bottom of the refill and the double-layer glass refill is completed.

This is why there is a small protrusion at the bottom of the refill, and once the protrusion is broken, the double-layer refill cannot maintain the vacuum state, and the heat preservation effect is very poor.

The inside of the thermos is coated with a thin layer of silver, which is as bright as a mirror, (there are also materials such as aluminum and copper), not mercury. Some people worry that silver is harmful to health. Thermos has been born for more than 100 years. At first, mercury was coated on the glass, but later for health and cost reduction, it was changed to silver plating. The inner liner of the thermos bottle is double-layered, and the silver is coated in the interlayer, so it will not come into contact with boiling water and has no effect on health.