text: In 2007 it was reported that a preliminary dating of a Pločnik copper workshop with a furnace and copper tools to 5,500 BCE, if correct, indicated the Copper Age could have started in Europe 500 years or more earlier than previously thought. The sophisticated furnace and smelter featured earthen pipe-like air vents with hundreds of tiny holes in them. Also there was a chimney to ensure that air goes into the furnace to feed the fire, and smoke comes out away from the workers. Copper workshops from later periods thought to indicate the beginning of the Copper Age were less advanced, lacked chimneys and workers blew air on the fire with bellows.
  In 2008, a copper axe was found at Pločnik that was dated to 5,500 BC. This pushed back the start of the Copper Age by 500 years.
  A study published in December 2013 reported an in situ discovery of a tin bronze foil from Plocnik dated to . This is the oldest tin bronze so far found in the world - a significant technological advance.
  This discovery was further supported by a reanalysis of 14 other tin bronze artefacts from neighbouring sites in Bulgaria and Serbia dated to before 4000 BC. This showed that early tin bronze was more common than previously thought, and developed independently in Europe 1,500 years before the first tin bronze alloys in the Near East.
  Another artifact similar to the Plocnik foil is a bronze ring from :fr:Gomolava in Serbia. When analyzed, the ring showed that it has above 8% tin content. The Plocnik foil has 11.7% tin. Tin bronzes above 8% tin require the high annealing temperatures in the range of 500–800C, so this was the temperatures already achieved at that time. These are considerably higher that the temperatures needed for the production of copper artifacts.
  According to the authors, the next horizon of bronzes in Serbia is dated to the third millennium BC, so this means there was a significant interruption, when this technology appears to have been lost. In Bulgaria, on the other hand, the production of bronze continued in the fourth millennium BC, but only arsenic bronzes were produced; so this was a different technology. In Serbia, likewise, mostly arsenical bronzes were produced in later times.