Glass pearl necklace

There are records of imitation pearls as far back as the Roman Empire, through the Middle Ages and into Renaissance Europe. Techniques for making them have varied.

Leonardo da Vinci's recipe for glass pearls:

If you wish to make a paste out of small pearls, take the juice of some lemons and put them to soak in it, and in a night they will be dissolved... Then wash the said paste with clear water a sufficient number of times for it to lose all trace of the lemon juice. After this let the paste dry so that it turns to powder. Then take white of egg, beat it well and leave it to settle and then moisten the said powder with this so that it becomes a paste again. And from this you can make pearls as large as you wish, and leave them to dry. Then place them in a small turning lathe and polish them, if you wish, with a dog's tooth, or if you prefer a polishing stick of crystal or chalcedony.