Since the summer we have experienced a sharp rise in demand for certain gold products. The one-kilo bar has become very popular," said Fiorenzo Arbini, in charge of health and safety at Pamp, another large Swiss refiner.
"People used to buy certificates, now they want physical gold."
Schnellmann said the Argor-Heraeus smelter is operating at full capacity, three eight-hour shifts a day. Conquering the backlog by hiring is difficult, because each candidate has to undergo a security check.
Gold refiners were established in Switzerland to supply the watch industry and, later, jewellery-makers in Italy.
Switzerland's largest banks stepped in to replace a void in gold trading while the London gold market was shut after World War Two and again during a brief closure in 1968.
The former Soviet Union, another top gold producer, chose Zurich banks to handle most of its gold sales in the 1970s and 1980s.
"Gold has an image of being the asset of last resort. This could be viewed as old-fashioned but this is how enough people with enough money to matter think," said Stephen Briggs, a metals strategist at RBS Global Banking & Markets.