What is the principle of anti-fog spray?

[DominicLee]

The principle of anti-fog spray is to utilize the hydrophilic groups in the formulation to adsorb water molecules in the air and reduce their surface tension, thereby decreasing the contact angle between water molecules and the surface of transparent objects. Before water molecules can form tiny droplets on the surface of the transparent object, they wet and spread across the surface, forming an ultra-thin transparent water film. This film no longer scatters incident light and does not interfere with vision, thus achieving an anti-fog effect. Below are the usage method of anti-fog spray and the reason why anti-fog spray becomes blurrier the more you wipe it: Usage method of anti-fog spray: Spray the anti-fog spray on the car glass and then wipe it clean to form a transparent protective film. This film can prevent water vapor from condensing into a fog layer on the glass, especially suitable for cold winters. Reason why anti-fog spray becomes blurrier the more you wipe it: After spraying the anti-fog spray, if you use a towel to wipe it, the anti-fog protective film on the laminated glass will be damaged, making it more likely for the anti-fog spray to become blurrier the more you wipe it. When this happens, the only solutions are to reapply the anti-fog spray or to ventilate the interior.

[AlexaFitz]

I often use anti-fog spray when driving in winter. It prevents the car windows from fogging up by forming a transparent film on the surface through the chemicals in the spray. This film reduces the surface tension of water, causing water vapor to spread evenly into a thin layer rather than forming droplets, thus maintaining clear visibility. I remember one heavy snow day when I used it, driving felt much safer and helped avoid potential accidents. This spray isn’t just for cars—it can also be used on bathroom mirrors or ski goggles at home. One application lasts for several days, saving the hassle of constant wiping. How convenient! When choosing a spray, it’s best to check the ingredients and opt for safe, non-toxic products. Avoid cheap, off-brand options as they might be harmful to the skin.

[SanAndrew]

Speaking of anti-fog sprays, my understanding is that they primarily rely on surfactants to work. These chemical ingredients reduce the surface tension of water, essentially creating an oil-resistant layer on the surface. When water vapor condenses, it spreads out evenly instead of forming obstructive tiny fog droplets. For example, it's similar to the waterproof coating we apply on umbrellas, but in reverse—it's designed to be hydrophilic. After trying it a few times, I found that this stuff works particularly well on car windows and home mirrors. After spraying, the fog disappears quickly, making driving visibility much clearer. Some sprays on the market even add long-lasting agents, where one application can last one to two weeks. However, be careful not to spray it on leather or electronic devices, as it may damage the material.

[DiJake]

I usually use anti-fog spray at home to treat bathroom mirrors and kitchen windows. The principle is simple: the spray creates a base layer on the surface, causing moisture to condense into a uniform film of water rather than blurry droplets, ensuring clear visibility when looking in the mirror or through the window. When purchasing, opt for an easy-to-spray type. Once applied, it saves you from constant wiping, making cleaning more effortless. The spray ingredients are generally safe, but any excess should be washed off immediately to avoid unsightly stains.