When the term "ballpoint pen" is used, what is generally meant is the writing implement that is probably the one most frequently used internationally. It is made primarily of plastic and consists of more than just the elongated polymer object with a clip to attach it to a chest or jacket pocket. When it is unscrewed, a reservoir - often made from a polymer material too - can be found inside, which acts as a storage container for the ink. Ballpoint pen inks contain at least one coloured metal oxide pigment and, as its main component, resin and organic solvent. The resin, which accounts for about 15 to 45 per cent of the ballpoint pen ink and is there essentially to determine the viscosity of the ink, is normally a blend of phthalate/alkyd, aldehyde and/or ketone resins, i.e. synthetically produced resin or, in other words, chemical substances / plastics. Alkyd resins belong to the polyester group and are produced in the course of condensation polymerisation of a multivalent alcohol like glycerine with dicarboxylic acid.