copper and Copenhagen buildings
/Børsen - the Exchange in Copenhagen. Dragon Spire 1625
Copenhagen City Hall completed 1905
Apartment building by the harbour about 1900 lit by evening sun
Copper and the copper alloys of bronze and brass are amazing metals with a long history of use in Denmark for a wide range of uses including making domestic vessels; for coins; for making weapons, particularly ornate weapons for ceremonial use or to display status, and copper and bronze, because they are relatively easy to work, have been used in jewellery and in the decorative arts, particularly for cast sculpture. From the late medieval period onwards copper and bronze have also been used on a much larger scale in architecture, for covering and protecting the roofs of important buildings and, again, because the metals are durable but relatively easy to work and because they can be used as thin sheets that can be shaped and joined together, copper is particularly good for covering domes and spires where the metal layer can be supported by a strong formwork or framework.
Pure copper is found naturally as an ore that has to be processed or refined to separate out the metal itself which, initially, is a bright pink red in colour but with exposure to air the surface oxidises - particularly near the sea where salts in the air effect the process to produce copper sulphate. The surface of the metal gains a patina that can be a shockingly sharp and bright green and can have irregular stain marks and what appears to be a surface crust. The change to the surface can take five years or more and in some situations thirty years or more but then it forms a complete protective surface that stops further degradation of the material underneath.
ornate Bronze Age weapons in the Danish National Museum
Working with copper is amazing … if it is heated to melting point it can be formed into shapes in moulds but sheets of the metal can also be manipulated and beaten into shape with a hammer - like working iron on an anvil - or can be drawn out into wires and twisted or plaited and it can be joined by welding. Beating out with a hammer, to form a shape or a vessel like a bowl, is often done on a sand-filled leather cushion with a hammer with a rounded end. Beating and working changes the characteristics of the metal so that it becomes harder and more rigid but if it is reheated the original malleability returns although the shape formed is retained so more and more extreme shapes can be achieved.
Combining copper with another metal to form an alloy also changes the workability and final appearance and hardness or durability of the metal so when copper is combined with tin it forms the alloy bronze that has a lower melting point so the metal can be used more easily for casting but is also more resistant to corrosion. Copper with zinc, forms the alloy brass that also has a lower melting point for casting in a moulds but can also be turned in a lathe. Brass has a darker and heavier brown colour, itself attractive, but it has another interesting quality in that it resists microbes so was a natural choice for door handles and for the handrails of staircases particularly in hospitals but actually for anywhere with heavy public use and where people were or are concerned about the transfer of germs.
alloy handle Vesterport building Copenhagen 1931
Not only can copper sheet or thin sheets of the copper alloys be cut and formed into complex 3D shapes but separate sheets can be joined by using rivets or sheets can be welded together, to form water tight vessels, for instance for brewing, or can be crimped or folded together to form weather-tight joins that can be used over large areas to form a light roof covering for domes or dormer windows or spires, particularly if there is also decorative work. Copper is much lighter than clay tiles or stone slates and certainly much lighter than alternative metals, lead or steel, when used for roof coverings and drains and downpipes. Climb one of the church towers or climb up the Round Tower in the centre of Copenhagen and look over the city and you can see just how many of the important roofs and spires and domes in the city are covered with copper.
That copper and its alloys can be cast in a mould but then cut and worked or finished, has made it an important material for decorative work and statues, which, with a form work beneath, can be of almost any size … think Statue of Liberty.
