Let's analyze the causes and treatment methods of fogging on the glass door of the refrigerator

What are the characteristics of the glass on the glass door of the refrigerator?
Isotropic: The molecular arrangement of glass is irregular and its molecules are statistically uniform in space. In an ideal state, the physical and chemical properties of homogeneous glass (such as refractive index, hardness, modulus of elasticity, coefficient of thermal expansion, thermal conductivity, electrical conductivity, etc.) are the same in all directions.
No fixed melting point: Because glass is an amorphous mixture, it has no fixed boiling point.

The transition of glass from solid to liquid occurs within a certain temperature range (ie softening temperature range), which is different from that of crystalline materials and does not have a fixed melting point. The softening temperature range is TG?T1, where TG is the transition temperature, T1 is the liquidus temperature, and the corresponding viscosities are 1013.4 DPA·s and 104?6dpa·s respectively.

Metastability: Glassy materials are usually obtained by rapidly cooling the melt.

When it changes from a molten state to a glass state, the viscosity increases dramatically during cooling, the particles do not have time to align regularly to form crystals, and the latent heat of crystallization is not released. Therefore, the glassy material has higher internal energy than the crystalline state, and its energy is between the molten state and the crystalline state, belonging to the metastable state. From a mechanical point of view, glass is an unstable high-energy state, for example, there is a tendency to transition to a lower-energy state, ie, there is a tendency to crystallize.

Therefore, glass is a metastable solid material.
Gradient change is reversible: the process of glassy material from molten state to solid state is gradual, and the change of its physical and chemical properties is also continuous and gradual. This is obviously different from the crystallization process of the melt.

New phases will appear during crystallization and many properties will change abruptly around the point of crystallization temperature. Glassy materials go from the molten state to the solid state over a wide temperature range. As the temperature is gradually lowered, the viscosity of the glass melt gradually increases, and then a solid glass is formed, but no new phases are formed in the process.

In contrast, the process of heating and melting glass is also gradual.