What is the inner liner of a stainless steel thermos made of?

There are two main types of materials used for the inner liner of stainless steel thermos flasks:

1. Stainless Steel: Stainless steel thermos flask liners typically consist of two layers of stainless steel, with a vacuum gap in between. This type of liner offers excellent corrosion resistance and durability, and is not easily broken.

 

2. Glass: Glass thermos flask liners consist of two layers of glass, also with a vacuum gap. The surface of the glass liner is usually coated with metals such as mercury or aluminum to reduce heat transfer. The glass surface may also be coated with a bright silver film to reflect infrared radiation, further improving insulation.