King Charles VI believed he was made of glass.

Famous Figures

T he first part of Charles VI’s reign in France seemed promising: He brought in more competent advisers and humane policies, earning the nickname “Charles the Beloved.” Unfortunately, history would remember him by another name: “Charles the Mad.” One of the king’s strangest symptoms? He believed he was made of glass. He even wore special clothing to avoid shattering. And he wasn't the only one.

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By the Numbers

Year Charles VI was crowned at age 11 and his uncles took over

1380

Year the first medical treatise to mention the glass delusion was published

1561

Did you know?

Clear glass wasn’t invented until the 15th century.

Clear glass is so common today that it’s easy to assume it has always existed. But for most of history, glass had a noticeable tint. Traditional glass is made from silica (sand), lime, and soda ash. Because these materials naturally contain impurities, early glass usually appeared greenish or slightly cloudy. Roman glassmakers experimented with additives to reduce the color, but producing consistently clear glass proved difficult. That changed in 15th-century Venice, one of Europe’s leading glassmaking centers. In the late 1400s, glassmakers on the Venetian island of Murano developed a remarkably pure glass known as cristallo. Using refined quartz sand and potash, they created glass that was nearly perfectly transparent, resembling natural rock crystal. The clarity of cristallo made it highly prized and helped spur new technologies, including magnifying lenses and reading glasses.