Red gallbladder adopts double-layer lead-free copper-plated glass liner. Copper plating is generally on the outer layer of the inner container, which will not contact with water and will basically not affect human health. However, asbestos is contained in the interlayer of white gallbladder, which is harmful to human health.

When buying a thermos, you can tap the glass layer of the bottle with your fingers. If the sound is clear, it is a good bottle, without cracks. When the external glass breaks the bottle, the glass in the bottle will hum, which is the sound produced by air convection in the glass.