Is it Possible to Make Roman Flexible Glass?
Today, the story of Roman flexible glass is mainly treated in the same manner as it had been by Pliny, i.e. with much doubt. Nevertheless, there have been some speculations on how this glass may have been made. One of these, for instance, is that the Roman glass-maker had somehow had access to boric acid or borax, both of which can be found naturally. By adding a small percent of boric oxide to the glass mixture, the end result would be something that was relatively unbreakable. It may be added that borax was imported from the East into Europe on a regular basis during the Middle Ages, and it was used by goldsmiths as a flux.
Boric acid could also be found in the steam vents of the Tuscan Maremma to the north of Rome, though this was supposedly only realized during the 19th century. Nevertheless, it is possible that the glass-maker may have stumbled on this source by chance. In any case, it is likely that the recipe for Roman flexible glass, if it did exist at all, will continue to elude us, and remain a ‘lost invention of the Romans’.