What is the difference between a red glass bulb and a white glass bulb?

Red glass liners and white glass liners are both common types of glass liners found in thermoses. While their primary function is to retain heat, there are actually significant differences when it comes to materials, craftsmanship, and safety. These differences directly impact our comfort and safety during use, making them key factors to consider when selecting a thermos.

First, let's talk about materials. Most white glass liners are made of ordinary borosilicate glass, which is silver-white in color because it contains no iron. However, be aware that some cheap, low-quality white liners may include asbestos between the double layers of glass to improve heat retention-a practice that could pose health risks with long-term use. In contrast, red-lined glass thermoses use rutile-type borosilicate glass, which contains a small amount of iron, giving it a reddish hue. This material is more stable and less prone to cracking when filled with boiling water due to temperature differences. Furthermore, they are manufactured in strict compliance with national standards, ensuring the inner layer is completely free of asbestos, making them safer to use.

Looking at craftsmanship, the manufacturing process for white glass liners is relatively simple-it's a basic double-walled vacuum structure with no additional treatments, resulting in lower costs and a more affordable price. Glass red liners, however, are different. They employ a "double-layered lead-free glass with an inner copper-plated layer" process. The copper-plated layer locks in heat more effectively, providing not only superior insulation but also greater durability. Since the manufacturing process is more complex, the cost is naturally higher. In terms of safety, qualified red-lined glass kettles do not leach heavy metals such as lead or cadmium, making them safe for use in households with the elderly, pregnant women, and children; whereas inferior white-lined kettles may contain asbestos residues, which could pose health risks with long-term use.