No eye glasses when dating
In particular, in the form of letters of the dukes of Milan, Francesco and Galeazzo Maria Sforza, dated 14 respectively, reveal the first detailed information about spectacles since their invention; namely, 1.
Florence was producing in large quantities not only convex lenses for presbyopes, but also for myopes (i.
Each glass was first ground on its back surface and then surrounded by a crude frame and given a handle.
They were then manufactured in England beginning in the 15th century.
Other centers of production like Germany, France, and Netherlands began to appear more frequently in the sources only by the sixteenth century but they never produced anything near the quantity of the Florentine documentation until well into the seventeenth century.
Ordinary “run-of-the-mill” spectacles cost the buyer just 2 or 3 soldi (shillings). The finest examples with quality crystal/glass lenses and gold or silver frames were priced at 1 ducat (the equivalent of 82 soldi). As an example, a mason from Florence in the 15th century made 17 soldi per day so multiple pairs were frequently ordered.
They were not the expensive vision aids of the clergy, the wealthy, and intellectuals, but instead were extensively used by artisans as well.
Stone grinding advanced especially around monasteries. English Franciscan Friar Roger Bacon (1220 -1292), in his 1268 ‘Opus Majus’, noted that letters could be seen better and larger when viewed through less than half a sphere of glass (plano-convex shape).