How copper changes it appearance
Copper has been used in design and architecture for thousands of years, in fact all the way back to ancient Egypt , where it was used to clad the massive doors of the temple of Amen-Re at Karnak (Copper Development Association Inc. 2022). This is due to its versatile nature and malleable attribute, but it as has aesthetic features when it weathers and changes colour to different climates. In most countries copper weathers naturally to a blu-green colour or patina over years. In dry climates the colour changes to a nut brown which is different to the patina colour and oxidisation that occurs due to moisture. This patina is actually a protective barrier that stops corrosion, unlike rust that forms on steel and iron. This also is anti-microbial that stops algae and keeps roofs clean and free from degrading.
Copper its uses and forms
Within the UK and Europe copper was extensively used on castles and cathedrals as decorative and functional. The Statue of Liberty in New York Harbour was sculpted using over 160,000 pounds of copper (Copper Development Association Inc. 2022). The other benefits of copper in structures and buildings is its light weight and availability to press into a thin flat sheet. Other materials like steel, iron, brass, gold and silver are much heavier and less abundant than copper. The copper used within the architectural application is commonly used in sheet or strip form. In these forms copper has a number of EN standards (EN1172) and thickness depending on its uses. Copper sheet is supplied to EN1653 and EN1652 with various hardness levels. These hardness levels determine the malleability and ultimately the use and application.
Copper is a natural product that weathers and patinas due to its climate and periods of time that it is exposed to the elements. There is a natural weather colouring chart that is useful to understand the colours to be expected and the timelines it takes. These colours are determined by the exposure to oxidising agents which can change depending on the location of the property. Metropolitan, marine and industrial areas where there is higher levels of pollutants exist, copper sulphate can appear on the surface which is the reaction of the acid being neutralised on the surface. Once again though the patina effect is crucial here to protect the surface against these weathering agents.This natural barrier against corrosion and degrading is another reason why copper has stood the test of time for 1,000’s of years.
Copper and considerations for use
Copper can have some usual relationships with other materials and also in the way that it is structural used and considered. These can be seen in the way it weathers and lasts and one example is with the soldered joints that change the appearance. There is also a choice in substrate which can effect how copper develops over time. The recommended substrate is wood and specifically kiln-dried and with smooth joints (Copper Development Association Inc. 2022, p.15). There is also the consideration for joints and seams and also the span of flat copper which can be subjected to buckling. With all construction materials the correct usage is imperative for longevity, but one characteristic is often forgotten and this is coppers high electrical conductivity that can effect radio frequency and needs to be considered for grounding. This characteristic has been known about for years with regard to lightening strikes and the conductivity, hence why copper roofs have always resorted to lightening protection systems, conductors and ground components.
Copper architectural features
The use of architectural copper is widespread throughout the world and visiting any city or town in the world and copper clad roofs are distinctive in their green colour. This green colour or patina is actually making the copper more durable and long-lasting. This is predicted to allow copper to have a life span of over 1,000 years. There is also a specific structure that adds to this longevity and it is the dome shape often associated with historic building and multiple structures within it. Examples of these are the Berlin Cathedral Church (1465), the Belvedere Palace in Vienna (c.1700) and the more recent the Millennium Centre in Cardiff, Wales (2000). This roof is actually steel but is treated with copper oxide to create the bronze colour and distinctive copper appearance.
Copper Development Association Inc.(2022) Copper in Architecture : A comprehensive compilation of designs, details and specifications. Available at www.copper.org/publications/pub_list/pdf/A4050-Architectural-Handbook.pdf [Accessed online : December 2022]