Chewing gum production. Factory worker checking mixing vats containing gumballs in a chewing gum factory. Chewing gum is made up of a water soluable gum-base, which is melted at a temperature of around 115 degrees Celsius. It is then filtered through a fine mesh screen. After further refining, it is placed into mixing vats (seen here) where other ingredients such as sugar, glucose, food colourings, flavourings and preservatives are added. Photographed in Oakland, California, USA.