A Brief History of Zinc and
Copper Roofing
Zinc
The ancient Babylonians and
Assyrians used zinc as part of the alloying process to produce brass but it was
in the 13 th century that India first obtained metallic zinc through smelting.
The process was passed on to China where zinc coins were produced during the
Ming Dynasty. It was not recognised as a separate metal in Europe until 1546.
The
metal did not even have a universally accepted name at this time, being known as
tutanego, Indian tin, calamine or spiauter. The term "zink" was first used
around 1536 from the German word "zinke" meaning sharp point which described the
shape of the metal deposits in the furnace.
By 1720 zinc was being produced
in industrial quantities in Swansea using imported oriental methods. In 1743
William Champion built the first European zinc smelter in Bristol producing 200
tonnes of zinc a year. While zinc casting was common, in 1805 it was discovered
that the metal could be rolled at temperatures of 100o to 150o
C to produce zinc sheeting.
Zinc is mined, mostly
underground, in more than 50 countries, with Australia, Canada, China, Peru and
the U.S.A. the leading producers. The ore contains many impurities and goes
through a concentration process before smelting.
The main use of
rolled zinc sheet and strip is for roofing, cladding, flashings, rainwater goods
and historically, even to imitate ornamental stone carvings. It has been used
extensively for these purposes in continental Europe since the 19th
century but now, with increased awareness of its technical and aesthetic
qualities, its use is rapidly increasing in the UK.
Today's zinc is a
zinc-copper-titanium alloy. It has an excellent visual appearance, long life
with minimal maintenance, and a cost-effectiveness and versatility which enables
it to be used for innovative architectural designs.
Copper
Copper was known to many of the
world's oldest civilizations and has been in use for at least 10,000 years. In
Roman times it was mined in Cyprus, giving rise to the metal's name of Cyprium,
later shortened to Cuprum and eventually Anglicised into English as
copper.
Today most copper is produced from
open cast mines on all five continents. The copper is extracted from vast
quantities of ore, mainly copper sulphides, by smelting, before being refined by
electrolysis in huge tank houses. In the early 18th century about 90%
of the world's copper was smelted in South Wales.
Copper has been used as a waterproof
roofing material since ancient times and can be recognised by the greenish roofs
and domes on today's buildings. This colouring is the reaction of air with
copper which creates an additional protection against corrosion. Firstly copper
oxide forms, followed by cuprous and cupric sulphide then subsequently the green
layer of copper carbonate, called verdigris or patina.
Copper is rolled to thicknesses
ranging from 0.5 to 1.0mm, but 0.6 to 0.7mm thickness is usually used for
roofing. It can be worked at any temperature and does not become brittle in cold
weather. It is available in sheets or strips and is generally regarded as a
lightweight covering requiring a substrate such as boarding.
Today, tried and tested fixing
details and techniques make copper the ideal trouble-free building material for
roofing, cladding, flashings, gutters, downpipes and other architectural
details. Advances in prefabrication techniques and machinery and fixing
technology have greatly reduced costs, which enables copper to be used in a
greater variety of building situations than in the past.
Copper roofs have been known to last
for over 700 years, the substrate rather than the copper itself eventually
failing.
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