The formation of streaks on glass is a daily phenomenon that is often attributed to poorly performed cleaning or ineffective products. In reality, behind those annoying opaque streaks, precise physical principles are hidden, explained in a clear and informative way by Professor Vincenzo Schettini, a well-known face of the project The physics we like. Understanding what happens on the surface of the glass during cleaning allows you to avoid common mistakes and obtain truly brilliant surfaces, without visible residues.
What are halos on glass
From a scientific point of view, the halo is nothing more than a solid residue left on the glass after the evaporation of water. Surface cleaners contain surfactants, molecules designed to bind to dirt and carry it away with the water. The problem arises when this mixture is not completely removed. If the water evaporates too quickly, as happens in direct sunlight, the surfactants remain anchored to the glass together with the dirt particles, creating that opaque effect that we perceive as a halo. It is therefore not the glass that is dirty, but the result of unbalanced evaporation that leaves visible chemical traces.
Because the water temperature is decisive in cleaning glass without streaks
An often underestimated aspect concerns the temperature of the water used. Hot water plays a key role because it reduces the viscosity of detergents, making them more fluid and less likely to stick to the surface. Furthermore, heat weakens the bonds between dirt and glass, making it easier to remove mechanically. Using hot water with a little soap therefore allows you to dissolve impurities better and rinse more effectively, preventing the surfactants from remaining trapped on the glass. It’s a delicate balance: more product doesn’t mean cleaner, but often the opposite effect.
Raw potato as a natural alternative to chemical surfactants
Among the most curious, but scientifically based solutions, emerges the use of raw potatoes as an ecological method for cleaning windows. The inside of the potato is rich in proteins and pectins, substances capable of lowering the surface tension of water in a similar way to industrial surfactants. By rubbing a potato cut in half on a previously dusted glass, these natural molecules help remove dirt without leaving chemical residues. The final, fundamental step is always rinsing thoroughly with water alone, which eliminates all traces and restores transparency to the surface.
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