A mirror is metal laid down so flat that its bumps are smaller than light itself. That is the whole trick, and sugar is what pulls it off.
Ammoniated silver nitrate holds silver as a dissolved ion, Ag⁺, suspended in ammonia. Drop in a reducing sugar like glucose and its aldehyde group hands electrons straight to that silver. Each ion grabs one electron and drops out as solid metal. The sugar oxidizes to gluconic acid in the same step.
Because the reaction runs slowly across the entire surface at once, the silver plates out atom by atom instead of clumping. It settles into a continuous film about 100 nanometers thick, thinner than a single wavelength of red light.
That thinness is the entire point. Every metal reflects, but a surface only reads as a mirror once it gets smoother than the light landing on it. Rough silver scatters that light and looks like grey powder. Smooth silver throws it straight back and you see your own face. Liebig's bath produced that smoothness with no polishing at all.
Before 1835, making a mirror meant pressing tin foil onto glass and flooding it with mercury to form an amalgam. The finish came out cloudy, the metal was heavy, and the workers who breathed mercury vapor all day paid for it with their nervous systems. Liebig swapped a slow toxic craft for a liquid you pour.
The reflection in your bathroom this morning was a frozen electron transfer. Sugar let go of electrons, silver caught them, and the metal locked in place flat enough to show you yourself.
Massimo (@Rainmaker1973)
Although mirrors have been around for thousands of years, a German chemist made a breakthrough in 1835 that would make the modern manufacture of them possible.
Add some sugar to ammoniated silver nitrate, pour it onto glass: you’ve got yourself a mirror.
Video
— https://nitter.net/Rainmaker1973/status/2070879826035229169#m