What is Borax? Office for Science and Society - McGill University

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One day a craftsman showed up in the court of Tiberius, Emperor of Rome (14AD to 37AD), to present the ruler with a beautiful transparent glass vase. Just as he was about to hand the vessel to Tiberius, the man let the vessel slip through his fingers. Everyone jumped, expecting a crash and flying glass. Roman glass after all had a history of fragility. But the glass did not break! Tiberius was very impressed and asked the glassmaker for the secret of the unbreakable glass. The craftsman was unwilling to divulge his method and boasted that he alone would be the keeper of the secret. This did not sit well with the ruthless Tiberius who had the glassmaker put to death. It is likely that the unfortunate artisan had accidentally stumbled on a method of making borosilicate glass. Ordinary glass is made by heating together sand, limestone and sodium oxide, a process that was well known to the Ancient Romans. If certain boron compounds are added to the mix, the glass becomes shatter resistant. This is the kind of glass we regularly use today in laboratories. Sodium borate, or borax, as it is better known, was used by Roman goldsmiths as a "flux," a substance added to the metal to make it flow more easily when heated. Perhaps the glassmaker added some borax to his molten mix to improve its flow properties and noted that the resulting glass was much stronger. The Romans never did discover the secret and it was only in 1916 that an American patent officially described shatterproof "Pyrex" glass containing a high percentage of boric oxide. Pyrex can withstand extreme temperature changes without cracking and is ideal for baking dishes. Borax was a rarity in ancient Rome, found only around some hot springs in Tuscany. But then in the 13th century Marco Polo returned from the Orient with samples of gunpowder, spaghetti and white crystals of borax. The Italians immediately figured out that they could make spaghetti themselves, but the borax had to be imported. Caravans were organized and soon Venetian goldsmiths were blessed with an ample supply of this ideal welding flux. Europeans also learned that the Chinese used borax in pottery glazes and began trying it themselves for this purpose. Addition of borax to improve the flow qualities of molten glass was a natural extension of this process. But the substance was still hard to come by. Most of the world supply of borax now comes from a gigantic open pit mine in California near a town that has been appropriately named Boron. There are now a myriad uses for the material which started its technological life as a gold flux. It is used to make glass for car headlights, enamel for stoves and refrigerators, ceramic tiles, antiseptics, bleach for unbleachables, weed killers and fertilizers. Thin fibres made from elemental boron are used to reinforce resins destined for aircraft and space vehicle parts. Boric acid, which is made from borax, can be used to control cockroaches. A bait made with flour and sugar and spiced with boric acid is likely to be their last supper. Even if they choose not to dine, the crystals of boric acid stick to the exoskeleton and rub away the oily protective layer. The creatures dehydrate and die. Ants suffer a similar fate.