text: Wrought iron is redshort or hot short if it contains sulfur in excess quantity. It has sufficient tenacity when cold, but cracks when bent or finished at a red heat. Hot short iron was considered unmarketable.
  Cold short iron, also known as coldshear, colshire, contains excessive phosphorus. It is very brittle when cold and cracks if bent. It may, however, be worked at high temperature. Historically, coldshort iron was considered sufficient for nails.
  Phosphorus is not necessarily detrimental to iron. Ancient Near Eastern smiths did not add lime to their furnaces. The absence of calcium oxide in the slag, and the deliberate use of wood with high phosphorus content during the smelting, induces a higher phosphorus content (typically <0.3%) than in modern iron (<0.02–0.03%). Analysis of the Iron Pillar of Delhi gives 0.11% in the iron. The included slag in wrought iron also imparts corrosion resistance.
  Antique music wire, manufactured at a time when mass-produced carbon-steels were available, was found to have low carbon and high phosphorus; iron with high phosphorus content, normally causing brittleness when worked cold, was easily drawn into music wires.  Although at the time phosphorus was not an easily identified component of iron, it was hypothesized that the type of iron had been rejected for conversion to steel but excelled when tested for drawing ability.
  History