What Are Cinderella’s Shoes Made Of?
Cinderella's shoes are actually an alloy of lead oxide - PbO - with silica, a sodium or potassium compound (soda or potash) and small additions of other oxides.
Although lead-potassium-silicate glasses are more expensive than lime glasses, it is easier to melt them and manufacture. This allows using high concentrations of PbO and low concentrations of alkali metal without affecting the fusibility. The high content of lead monoxide yields a high refractive index and a high dispersion value - two parameters of particular importance in some optical applications, as they make the product shiny and bright.
When a painter looks at the Mona Lisa, they can, of course, define the mixture of paints and paint additives; when an actor watches a soap opera, they do not follow the plot but check for the failed scenes instead; when a typographer looks at the money, they are interested in the quality of printing. Authors of such claims can project them ad infinitum, but what we are really seeing is not the chemical or physical structure of the material but a mythologised perception of it.
One such enigma is lead glass. Perhaps gold is the only element in humanity's history that has been more often associated with wealth than this - whether natural or man-made - mineral. There is no point in mentioning all the stories about Bohemian glass. Still, it is worth noting that, for instance, every Soviet family - and there were at the very least 100 million of them - believed a Czech crystal chandelier was an attribute of welfare. Even if they hung their lamps in Khrushchev-era apartments.
People sang songs about lead crystal - Vladimir Vysotsky, who emphasised the secondariness of metals, among them. "The crystal house in the mountain is for her... My springs are of silver, And my mines are of gold!"
A town in Vladimir Oblast was named after lead glass: Gus-Khrustalny. And the word 'Holocaust' originates from the "Night of Broken Glass" of 1938, despite the 'night' itself has nothing to do with crystal.
An interesting question is why so much attention was paid to silicon dioxide and not emeralds, agates or rubies. It is not beauty that is considered here but ancient Greek myths that today's men and women take as an axiom. According to the legends, the marble statue of Galatea can be revived, and water and ice can be transformed into another substance - crystal. In other words, our subconscious sees it as 'dead water' - the universal healing balm, also in Russian fairy tales.