Copper, Brass, and Bronze Surfaces E-Book

L. William Zahner

• Herausgeber: John Wiley & Sons
• Kategorie: Geisteswissenschaft
• Serie: Architectural Metals Series
• Sprache: Englisch

Seitenzahl: 522

Veröffentlichungsjahr: 2020

Beschreibung

A FULL-COLOR GUIDE FOR ARCHITECTS AND DESIGN PROFESSIONALS TO THE SELECTION AND APPLICATION OF COPPER, BRASS, AND BRONZE Copper, Brass, and Bronze Surfaces, third in Zahner's Architectural Metals Series, provides a comprehensive and authoritative treatment of copper, brass, and bronze applications in architecture and art. If offers architecture and design professionals the information they need to ensure proper maintenance and fabrication techniques through detailed information and full-color images. It covers everything from the history of the metals and choosing the right alloy, to detailed information on a variety of surface and chemical finishes and corrosion resistance. The book also features case studies that offer strategies for designing and executing successful projects using copper, brass, and bronze. Copper, Brass, and Bronze Surfaces is filled with illustrated case studies that present comprehensive coverage of how each metal is used in creating surfaces for building exteriors, interiors, and art finishes. All the books in Zahner's Architectural Metals Series offer in-depth coverage of today's most commonly used metals in architecture and art. This visual guide: * Features full-color images of a variety of copper, brass, and bronze finishes, colors, textures, and forms * Includes case studies with performance data that feature strategies on how to design and execute successful projects using copper, brass, and bronze * Offers methods to address corrosion, before and after it occurs * Explains the significance of the different alloys and the forms available to the designer * Discusses what to expect when using copper, brass, and bronze in various exposures Written for architecture professionals, metal fabricators and developers, architecture students, designers, and artists working with metals, Copper, Brass, and Bronze Surfaces offers a logical framework for the selection and application of copper, brass, and bronze in all aspects of architecture.

Leseprobe

Table of Contents

Cover

Preface

CHAPTER 1: Introduction—Element 29

INTRODUCTION

COLOR

COLORS OF ALLOYS

COPPER MINERALS

HISTORY

THE MODERN COPPER PRODUCTION PROCESS

SUSTAINABILITY, ENVIRONMENTAL, AND HYGIENIC CONCERNS

COPPER AND WATER

HEALTH AND SAFETY

COPPER: THE ANTIMICROBIAL METAL

COPPER ALLOYS FOR THE ARTS

NOTES

CHAPTER 2: Copper and Its Alloys

INTRODUCTION

THE RICH HISTORY OF COPPER ALLOYS

ELEMENTS ADDED TO COPPER

ALLOY DESIGNATION SYSTEM

THE UNIFIED NUMBERING SYSTEM

TEMPERS

WROUGHT COPPER ALLOYS

BRASSES

LEADED BRASSES

TIN BRASSES

PHOSPHOR–BRONZE ALLOYS

ALUMINUM–BRONZE ALLOYS

SILICON–BRONZE ALLOYS

COPPER–NICKEL AND NICKEL–SILVER ALLOYS

CAST ALLOYS

RED BRASSES

YELLOW BRASSES

SILICON–BRONZE ALLOYS

A TIN–BRONZE ALLOY

NICKEL–SILVER ALLOYS

A MANGANESE–BRONZE ALLOY

NOTES

CHAPTER 3: Surface Finishes

INTRODUCTION

MILL SURFACES

MECHANICAL FINISHES AND TEMPORARY PROTECTION

COLOR FROM OXIDATION AND CHEMICAL REACTIONS

TEXTURES

TIN‐COATED COPPER

MELTED COPPER ALLOY SURFACING

COPPER AND GLASS

PROTECTING THE SURFACE

NOTES

CHAPTER 4: Expectations of the Visual Surface

INTRODUCTION

INTENT: AN UNCHANGED SURFACE APPEARANCE

INTENT: A SURFACE APPEARANCE THAT CHANGES NATURALLY

FLATNESS

TEXTURING THE SURFACE

INITIAL OXIDATION ON COPPER ALLOYS

IN SITU PATINATION

PREPATINATION

THE EFFECT OF SEALANTS

THE CAST SURFACE

ARRIVING AT THE BEST POSSIBLE OUTCOME

NOTES

CHAPTER 5: Designing with the Available Forms

A BRIEF HISTORY

WROUGHT FORMS

THE CAST FORM

NOTES

CHAPTER 6: Fabrication Processes and Techniques

INTRODUCTION

FORMING

V‐CUTTING

CUTTING COPPER ALLOYS

MACHINING

SOLDERING, BRAZING, AND WELDING

CASTING

CHAPTER 7: Corrosion Characteristics

GENERAL INFORMATION

CATEGORIES OF CORROSION

ENVIRONMENTAL EXPOSURES

ACIDS AND BASES

COPPER ALLOY SURFACE CATEGORIES

NOTES

CHAPTER 8: Maintaining the Copper Alloy Surface

INTRODUCTION

PROTECTING THE NEW COPPER ALLOY SURFACE

ACHIEVING PHYSICAL CLEANLINESS

ACHIEVING CHEMICAL CLEANLINESS

ACHIEVING MECHANICAL CLEANLINESS

REPAIRING PATINAS

PROTECTING THE SURFACES OF COPPER AND COPPER ALLOYS

CLEANING THE COPPER SURFACE

REMOVING COPPER STAINS FROM OTHER SUBSTANCES

DETERIORATING PATINAS

NOTES

APPENDIX A: Comparative Attributes of Metals Used in Art and Architecture

APPENDIX B: Hardware Finish Codes and Descriptions

APPENDIX C: Numbering Systems Used for Copper Alloys

Further Reading

Index

End User License Agreement

List of Tables

Chapter 1

TABLE 1.1 Electrical conductivity of various metals in siemens m

−1

at 20 °...

TABLE 1.2 Approximate percentages of elements in the Earth's upper mineral strat...

TABLE 1.3 Mineral forms of copper.

Chapter 2

TABLE 2.1 A few of the names given to alloys of copper.

TABLE 2.2 UNS number ranges for wrought copper alloys.

TABLE 2.3 UNS number ranges for cast copper alloys.

TABLE 2.4 A few common cold rolled wrought temper designations.

TABLE 2.5 A few common hot rolled temper designations.

TABLE 2.6 A few common temper designations of copper.

TABLE 2.7 True brasses.

TABLE 2.8 List of leaded copper–zinc alloys.

TABLE 2.9 List of nickel–silver alloys used in architecture.

TABLE 2.10 Common cast tempers.

TABLE 2.11 Common cast alloys.

Chapter 3

TABLE 3.1 Scotch‐Brite pad color and corresponding grit range produced.

TABLE 3.2 Buffing compounds used on copper alloys.

TABLE 3.3 Colors achieved using certain chemical compounds.

Chapter 4

TABLE 4.1 Coating comparisons.

TABLE 4.2 Coefficient of linear expansion of various copper alloys.

Chapter 5

TABLE 5.1 Comparison of alloying constituents of Muntz Metal with Architectural ...

TABLE 5.2 Approximate weights for copper sheet and plate.

TABLE 5.3 Typical widths available for plate.

TABLE 5.4 Standard lengths of sheets.

TABLE 5.5 Typical widths available for sheet stock.

TABLE 5.6 Correlation of weight thickness to nominal length thickness.

TABLE 5.7 Nominal foil thicknesses and unit weights.

TABLE 5.8 Several extrudable copper alloys.

TABLE 5.9 Several of the copper alloys available in wire form.

TABLE 5.10 Various strand configurations.

TABLE 5.11 Comparisons of casting methods used on copper alloys.

TABLE 5.12 Factors to consider for various cast methods.

Chapter 6

TABLE 6.1 Cutting methods used on copper alloys.

TABLE 6.2 Machineability of copper alloys.

TABLE 6.3 Leaded solders.

TABLE 6.4 Lead‐free solders.

TABLE 6.5 Common brazing alloys.

TABLE 6.6 Welding processes used on copper alloys.

TABLE 6.7 Various surface maladies seen on castings.

TABLE 6.8 Elongation of C11000 by temper designation.

Chapter 7

TABLE 7.1 Common mineral forms of copper.

TABLE 7.2 Various mineral forms of copper.

TABLE 7.3 Corrosion categories.

TABLE 7.4 Oxides of copper.

TABLE 7.5 A few of the minerals and associated colors of the patinas.

TABLE 7.6 Electrical potential of various metals in flowing seawater.

TABLE 7.7 ISO environmental exposure categories.

Chapter 8

TABLE 8.1 Levels in achieving physical cleanliness.

TABLE 8.2 Chemically clean surface levels for copper alloys.

TABLE 8.3 Relative hardness of substances on the Moh scale.

List of Illustrations

Chapter 1

FIGURE 1.1 Copper's position in the periodic table of elements.

FIGURE 1.2 Face‐centered cubic structure of a copper crystal.

FIGURE 1.3 Copper atom.

FIGURE 1.4 Sea of shared electrons around the metal atoms of copper.

FIGURE 1.5 Reflectivity of aluminum, silver, stainless steel, copper, and gold...

FIGURE 1.6 Image of different alloys and colors.

FIGURE 1.7 Color changes in brass alloys.

FIGURE 1.8 A naturally formed patina.

FIGURE 1.9 The Statue of Liberty.

FIGURE 1.10

Perseus with the Head of Medusa

, by Benvenuto Cellini.

FIGURE 1.11 Various minerals of copper.

FIGURE 1.12 Approximate time periods of major copper activity in ancient times...

FIGURE 1.13 Image of the Ontonagon copper boulder.

FIGURE 1.14 Roman helmets made from copper.

FIGURE 1.15 Giant cast Buddha at the Todaiji Temple in Japan.

FIGURE 1.16 Image of religious totemic items.

FIGURE 1.17 Bronze cannon.

FIGURE 1.18 Initial mill forms.

FIGURE 1.19 Examples of special‐order copper alloys with biocide properties fr...

FIGURE 1.20 Cast dragon ornamentation on the Town Hall in Munich, Germany.

FIGURE 1.21 A repoussé copper piece from Jerusalem.

FIGURE 1.22

Heartland Harvest

, Kansas City Board of Trade.

FIGURE 1.23 Copper spot price in US dollars per pound over a 30‐year period.

Chapter 2

FIGURE 2.1 Copper handrail and copper wire rope.

FIGURE 2.2 Panel system made of the C11000 alloy at the de Young museum in San...

FIGURE 2.3 Copper alloy C22000 in the Ohio Holocaust and Liberators Memorial,

FIGURE 2.4 Mirror polished C26000 alloy.

FIGURE 2.5 Polished C28000 alloy entryway.

FIGURE 2.6 Alloy C37700 was used on the artwork for the Museum of the Bible.

FIGURE 2.7 Extruded plates of alloy C38500 (Architectural Bronze) used for the...

FIGURE 2.8 Alloy C61000 form made from thin sheet.

FIGURE 2.9 Interior walls made of alloy C75200.

FIGURE 2.10 Art cutout using alloy C75200.

FIGURE 2.11 The use of alloy C83600 for the cast doors at the Kansas City Life...

Chapter 3

FIGURE 3.1 Heavy oxidation on a thick copper alloy plate.

FIGURE 3.2 Art deco nickel silver.

FIGURE 3.3 The aluminum–bronze alloy TECU Gold, produced by KME of Germany, wa...

FIGURE 3.4 Alloy C28000, polished and coated with clear Incralac, in use at th...

FIGURE 3.5 The de Young museum, 1.5‐millimeter‐thick copper sheets made into I...

FIGURE 3.6 Kiosk at the Midland Theatre, Kansas City, Missouri.

FIGURE 3.7 Comparison of the natural color of various alloys of copper.

FIGURE 3.8 A large cone of the naturally colored C22000 alloy with an Angel Ha...

FIGURE 3.9 Curved custom polished surface using the C22000 alloy.

FIGURE 3.10 A C11000 surface with in‐and‐out embossed bumps in a Prada store.

FIGURE 3.11 Heat‐generated color on copper alloy C11000.

FIGURE 3.12 Niello used on a bronze axe head and a helmet.

FIGURE 3.13 Ohio Holocaust and Liberators Memorial, Columbus, Ohio,

FIGURE 3.14 Custom doors made of the C22000 and C28000 brass alloys.

FIGURE 3.15 Bond Street window surrounds made of the C11000 alloy,

FIGURE 3.16

Left

: Addition to the Walker Art Building at Bowdoin College in Br...

FIGURE 3.17 Various Dirty Penny tones.

FIGURE 3.18 Dirty Penny on copper panels made of the alloy C11000 after three ...

FIGURE 3.19 Perforated and bumped Dirty Penny copper alloy C11000.

FIGURE 3.20 Fifty‐millimeter thick black copper plate by John Labja.

FIGURE 3.21 Robert Hoag Rawlings Public Library, Antoine Predock Architect.

FIGURE 3.22 Blackened copper alloys in three projects.

FIGURE 3.23 Three examples of red patinas.

FIGURE 3.24 Red patina on panels at the Daeyang Gallery and House, Korea,

FIGURE 3.25 The patinated copper roof dating to 1625 on Børsen and t...

FIGURE 3.26 Walls clad in prepatinated copper.

FIGURE 3.27 Patinated walls right after installation and several years later.

FIGURE 3.28 Roof and soffit surfaces in Hong Kong.

FIGURE 3.29 Various patinas that can enhance copper alloys.

FIGURE 3.30 Various artworks made of patinated copper.

FIGURE 3.31 Formation of patina.

FIGURE 3.32 Layering of patinas for the art wall in the Smithsonian's National...

FIGURE 3.33 Custom patination across multiple panel elements.

FIGURE 3.34 Cold patina blend over a surface.

FIGURE 3.35 Price Tower, Bartlesville, Oklahoma, designed by Frank Lloyd Wrigh...

FIGURE 3.36

Heartland Harvest

, Kansas City Board of Trade,

FIGURE 3.37 Green patina on

Muse of the Missouri

by Wheeler Williams (1963).

FIGURE 3.38

Left

: Gold patina cast door

Right

:

Black

...

FIGURE 3.39

Two Piece Mirror Knife Edge

by Henry Moore, East Building, Nationa...

FIGURE 3.40 French brown patina on cast pillar with bas relief, by Manuel Carb...

FIGURE 3.41 Repoussé and chasing work on ornamental panels.

FIGURE 3.42 Hammered copper surface used on a kitchen hood in a residence.

FIGURE 3.43 Deep hammering of copper surfaces.

FIGURE 3.44 Embossed copper.

FIGURE 3.45 Custom patterns pressed into thin sheet copper.

FIGURE 3.46 Tactile surface textures produced using CNC.

FIGURE 3.47 Copper wall reflecting off the glass in the fern court at the de Y...

FIGURE 3.48 Etched and darkened C26000 alloy.

FIGURE 3.49 Various examples of etched and engraved copper alloys.

FIGURE 3.50 Chemical milled C22000 plate below.

FIGURE 3.51

Top

: Laser‐etched names in Commercial Bronze (alloy C22000).

Lower

...

FIGURE 3.52

Left

: Silver plate on copper demonstration sample.

Right

: Chrome p...

FIGURE 3.53

Top

: Chrome‐plated

Fuga

, by Jan Hendrix.

Lower left

: Nickel plate ...

FIGURE 3.54 Tin‐coated copper.

FIGURE 3.55 Melted copper alloy surfaces.

FIGURE 3.56 Copper and glass.

Chapter 4

FIGURE 4.1 Newly installed copper on a roof in Minnesota and on walls in Texas...

FIGURE 4.2 Cuprous oxide forming on the C11000 panels used at the de Young mus...

FIGURE 4.3 Interference oxides developing on copper surfaces exposed to the at...

FIGURE 4.4 Distinct design paths for the use of copper alloys in art and archi...

FIGURE 4.5 Benzotriazole test.

FIGURE 4.6 Fireman's Memorial fountain sculpture. Designed by artist Tom Corbi...

FIGURE 4.7 Sketch of Incralac lacquer and a wax coating on a copper alloy.

FIGURE 4.8 Old wax showing signs of decay.

FIGURE 4.9 The

Muse of Missouri

and stains developing on its patina.

FIGURE 4.10 Copper alloy handrails showing signs of patina wear from human int...

FIGURE 4.11 Benzotriazole bond with surface copper.

FIGURE 4.12

Left

:

Heartland Harvest

, an artwork using the C11000 alloy at the ...

FIGURE 4.13

Bottom

: Differences in metal color tone below the clear film when ...

FIGURE 4.14 Newly installed thin copper sheathing.

FIGURE 4.15 Flat‐seam thin copper panels and expected direction of geometry ch...

FIGURE 4.16 Sheet width‐to‐thickness relationship to ensure flatness.

FIGURE 4.17 Examples of embossed copper sheet.

FIGURE 4.18 Cupric oxide forming on the surface of copper shortly after instal...

FIGURE 4.19 Cupric oxide changing with time of exposure.

FIGURE 4.20 Failure of in situ patination.

FIGURE 4.21

Left

: Prepatina on interior walls at the University of Toronto.

Ri

...

FIGURE 4.22 Sealant streaking below glazing.

FIGURE 4.23 Marks from a marking pen on a metal after 25 years of exposure.

FIGURE 4.24 Copper roof surface.

Top

: Initial installation.

Bottom

: After two ...

FIGURE 4.25 The surface of the National Underground Railroad Freedom Center de...

Chapter 5

FIGURE 5.1

Left

: Ancient formed spear;

top right

: ewer;

bottom right

: helmet m...

FIGURE 5.2 Etched cross‐section of an initial casting of copper.

FIGURE 5.3 Large slab of copper at the rolling Mill.

FIGURE 5.4 Large copper coils.

FIGURE 5.5 Thick copper plate.

FIGURE 5.6 Copper panels on the de Young museum in San Francisco.

FIGURE 5.7 Various copper roof types. Top left: batten seam; top right: standi...

FIGURE 5.8 Copper leafing.

FIGURE 5.9 An extrusion must fit within a circle whose size is determined by f...

FIGURE 5.10 (a–c) Examples of hollow, semihollow, and solid extrusions.

FIGURE 5.11 A box extrusion made from two sections that snap together.

FIGURE 5.12 Improvements to extrusion design to aid in metal flow.

FIGURE 5.13 A larger part created from a series of smaller extrusions.

FIGURE 5.14 Extruded brass with statuary finish on the Ohio State Supreme Cour...

FIGURE 5.15 Entertainment Building, Hong Kong.

FIGURE 5.16 Copper bar used as handrails at the Smithsonian's National Museum ...

FIGURE 5.17 Examples of different sized bars and rods used in art applications...

FIGURE 5.18 Copper wire rope used as an artistic feature on the handrails at t...

FIGURE 5.19 Three examples of expanded copper alloy.

FIGURE 5.20 Expanded patinated copper surface created from KME's TECU Patina M...

FIGURE 5.21 Fine mesh light diffuser.

FIGURE 5.22 Decorative copper alloy meshes.

FIGURE 5.23 Custom perforation of the C11000 alloy used in the Irving Conventi...

FIGURE 5.24 The C11000 alloy with a Dirty Penny finish, surfaced with bumps an...

FIGURE 5.25 Sand cast door handles made from silicon–bronze alloy C87300.

FIGURE 5.26 Cross‐section of a typical sand cast mold.

FIGURE 5.27

Throwing in the Towel

Chapter 6

FIGURE 6.1 Stress–strain graph of copper.

FIGURE 6.2 Hammered copper vase.

FIGURE 6.3 Ancient Roman helmet hammered out of copper alloy.

FIGURE 6.4 Various fabricated copper items.

FIGURE 6.5 Bending with and against the grain.

FIGURE 6.6 V‐cutting copper alloys.

FIGURE 6.7 V‐cut corner on panels at the de Young museum of art.

FIGURE 6.8 Shaping copper alloys.

FIGURE 6.9 Graph of change in yield strength as alloying elements are added.

FIGURE 6.10 Copper and copper alloy–clad surfaces.

FIGURE 6.11

Left

: Decorative leaf form by Reilly Hoffman.

Right

: Decorative gr...

FIGURE 6.12 Waterjet cut thick brass inserts.

FIGURE 6.13 Gate with waterjet cut angels.

FIGURE 6.14 Laser cutting in

Fuga

FIGURE 6.15 Laser cut artwork

FIGURE 6.16 The plasma cut copper artwork

Hands of Man

by the author.

FIGURE 6.17 Machined copper alloy parts.

FIGURE 6.18 Machining, texturing, and finishing of panels at the Museum of the...

FIGURE 6.19

Top

: Initial mill marks on the metal surface.

Bottom

: Computer ima...

FIGURE 6.20 Machined lettering at the Museum of the Bible, designed by Larry K...

FIGURE 6.21 Soldered joints in a copper roof.

FIGURE 6.22

Left

: Brazed copper with blown glass.

Right

: Brazed copper wire an...

FIGURE 6.23 Two solder joints on thin sheet material.

FIGURE 6.24

Left

: Welding of C22000 plates.

Right

: Welding of a handrail using...

FIGURE 6.25 Welding of a copper elbow for the Prada store in Tokyo.

FIGURE 6.26 Visible welds on weathered cast bronze.

FIGURE 6.27 Various examples of sand‐cast shapes, from simple to intricate.

FIGURE 6.28 Spun and polished copper hemisphere light sconce.

FIGURE 6.29 Plastic deformation zone before fracturing.

FIGURE 6.30 Custom perforating and embossing.

FIGURE 6.31 Custom embossed copper at the de Young museum of art

FIGURE 6.32 Roll embossed finish: (

top

) unaged surface; (

bottom

) a finish expo...

FIGURE 6.33 Diagram showing hold‐down clearance needed for custom embossing.

Chapter 7

FIGURE 7.1 Christ Church in Philadelphia, Pennsylvania, has the oldest copper ...

FIGURE 7.2

Top

: Hildesheim Cathedral has the oldest existing copper roof in Eu...

FIGURE 7.3 Statue of Liberty.

FIGURE 7.4 Cuprous oxide on a door made of copper plate.

FIGURE 7.5 Black cupric oxide formation on copper exposed to low pH and humidi...

FIGURE 7.6 Weathered copper alloy doors showing the presence of both oxides.

FIGURE 7.7 Casting made of the C87610 alloy near the seaside.

FIGURE 7.8 Prepatinated surface in Corpus Christi, Texas.

FIGURE 7.9 Polished Cartridge Brass (alloy C26000) showing tarnish from handli...

FIGURE 7.10 Green developing along the lower edge of a copper panel.

FIGURE 7.11 Makeup of a galvanic cell.

FIGURE 7.12 An idealized cold‐water connection where a copper pipe is joined t...

FIGURE 7.13 Stainless steel supports and the C22000 copper alloy in a chloride...

FIGURE 7.14 The galvanic circuit and the means to prevent it from occurring.

FIGURE 7.15 Dezincification on a C26000 surface.

FIGURE 7.16 Microscopic images of dezincification corrosion.

FIGURE 7.17 Fingerprints and handprints on different surfaces.

FIGURE 7.18 Cleaning compounds left on the surface.

FIGURE 7.19 Corroding steel support under a cast copper alloy handrail cap.

FIGURE 7.20 Relationship of metal temperature to ambient air temperature.

FIGURE 7.21 One‐hundred‐year‐old copper and brass time capsule.

FIGURE 7.22 Copper panels affected by moisture entering a crate.

FIGURE 7.23 Streaks on the upper regions of a sculpture.

FIGURE 7.24 The chlorides in deicing salts will affect copper surfaces.

FIGURE 7.25 Uncoated copper roof and walls.

FIGURE 7.26 Copper alloy art inserted in the terrazzo floor of Miami Internati...

FIGURE 7.27 (

Left

) Patinated copper art, (

middle

) roofs, and (

right

) walls.

FIGURE 7.28 Prepatinated copper surfaces: (

top

) successful and (

bottom

) unsucc...

FIGURE 7.29 Unprotected patinas on bronze.

FIGURE 7.30 Under‐film oxidation on brass.

Chapter 8

FIGURE 8.1 Tarnish on copper surface of a door made from thick copper plates.

FIGURE 8.2 Cleaning solution and handprint left on a copper alloy form.

FIGURE 8.3 Fingerprints on copper alloy surfaces.

FIGURE 8.4 Panels at the 9/11 Memorial darkening under the film.

FIGURE 8.5 Image of test results of ability of benzotriazole to prevent tarnis...

FIGURE 8.6 Bird waste on copper wall panels and a bronze sculpture.

FIGURE 8.7 Bird waste beginning to interact with the copper alloy used for

FIGURE 8.8 (

Left

) Bird waste, (

top right

) old wax, and (

bottom right

) Mill pri...

FIGURE 8.9 Deicing salt residue on surfaces.

FIGURE 8.10 Deicing salt damage to copper surfaces.

FIGURE 8.11 (

Left

) Old wax and (

right

) renewed wax on a bronze sculpture by th...

FIGURE 8.12

Muse of Missouri

by Wheeler Williams.

FIGURE 8.13 Microscopic image of the decaying coating.

FIGURE 8.14 Rust stains on the

Muse

sculpture from deposits in the water.

FIGURE 8.15 Cleaning copper alloy surfaces with mild soap and water.

FIGURE 8.16 (

Right

) Cleaning fluid left on a surface, (

top left

) iron rust sta...

FIGURE 8.17 Dark streaks of cupric oxide visible on old copper surfaces.

FIGURE 8.18 Cast copper alloy doors after decades of exposure.

FIGURE 8.19 Initial removal of oxides.

FIGURE 8.20 Much of the tarnish, old oxide, and patina was removed from the su...

FIGURE 8.21 Developing the statuary finish.

FIGURE 8.22 The restored doors are hung.

FIGURE 8.23 (

Left

) Removing oxides from C26000 alloy and (

right

) repolishing t...

FIGURE 8.24 Mechanical polishing of a copper alloy surface.

FIGURE 8.25 Laser ablation of copper surface.

FIGURE 8.26 Scratches through the protective layer and patina of three surface...

FIGURE 8.27 Packaging for Prada being prepared for shipping.

FIGURE 8.28 Steel corrosion products on several surfaces.

FIGURE 8.29 (

Left

,

top right

) Rust stains on cast sculpture; (

top right

) befor...

FIGURE 8.30 Blistering on the surface due to the core remaining inside the scu...

FIGURE 8.31 Antique light fixture before (

left

) and after (

right

) restoration.

FIGURE 8.32 XRF readings of the top section of the light fixture.

FIGURE 8.33 Cleaning the copper stain from a limestone base, before (

left

) and...

Guide

Cover

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ZAHNER'S ARCHITECTURAL METALS SERIES

Zahner's Architectural Metals Series offers in‐depth coverage of metals used in architecture and art today. Metals in architecture are selected for their durability, strength, and resistance to weather. The metals covered in this series are used extensively in the built environments that make up our world and also attract and fascinate the artist. These heavily illustrated guides offer comprehensive coverage of how each metal is used in creating surfaces for building exteriors, interiors, and art sculpture. The series provides architects, metal fabricators and developers, design professionals, and students of architecture and design with a logical framework for the selection and use of metal building and design materials. Forthcoming books in Zahner's Architectural Metals Series will cover steel and zinc surfaces.

Titles in Zahner's Architectural Metals Series include:

Stainless Steel Surfaces: A Guide to Alloys, Finishes, Fabrication, and Maintenance in Architecture and Art

Aluminum Surfaces: A Guide to Alloys, Finishes, Fabrication, and Maintenance in Architecture and Art

Copper, Brass, and Bronze Surfaces: A Guide to Alloys, Finishes, Fabrication, and Maintenance in Architecture and Art

Copper, Brass, and Bronze Surfaces

A Guide to Alloys, Finishes, Fabrication, and Maintenance in Architecture and Art

L. William Zahner

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Library of Congress Cataloging‐in‐Publication Data:

Names: Zahner, L. William, author.

Title: Copper, brass, and bronze surfaces : a guide to alloys, finishes, fabrication, and maintenance in architecture and art / L. William Zahner.

Description: Hoboken, New Jersey : Wiley, 2020. | Series: Zahner's architectural metals series | Includes bibliographical references and index.

Identifiers: LCCN 2019045098 (print) | LCCN 2019045099 (ebook) | ISBN 9781119541660 (paperback) | ISBN 9781119541677 (adobe pdf) | ISBN 9781119541684 (epub)

Subjects: LCSH: Copper. | Brass. | Bronze. | Architectural metal—work. | Art metal—work.

Classification: LCC TS620 .Z34 2020 (print) | LCC TS620 (ebook) | DDC 739—dc23

LC record available at https://lccn.loc.gov/2019045098

LC ebook record available at https://lccn.loc.gov/2019045099

This book is in honor of Salvatore Orlando.He was a good friend and advocate of the red metal.

Preface

The passage of time is reflected in the color of copper.

Of all the metals used in art and architecture, copper is the most engaging.

Throughout history, mankind has had a special relationship with copper. Copper has a weight and feeling of substance. It can be shaped and formed into useful objects, and more importantly, it has an appearance as natural as the colors of an oak forest in the fall: a color that shows value and the passage of time.

Power and force are needed to shape the other metals used in art and architecture. Copper, on the other hand, shapes and moves under the blows of handheld chasing tools. It can be easily folded, curved, stretched, and embossed. One gets close to the metal when working with copper.

Throughout human time copper and copper alloys have played different and expanding roles. Bronze sculptures of ancient deities and heroes have outlived their civilizations, even while resting under the sea for thousands of years. Copper has been mined by every major civilization and converted and cast into both useful tools and decorative statues.

The maritime world embraced copper alloys, particularly brass. Alloys with names such as Admiralty Bronze and Naval Brass recall a time when this metal served as biocladding on the underside of a ship and ornamentation on the top. Consider that the military term “brass” relates to someone of high rank: the one with the brass metals or the brass‐adorned hat.

Copper alloys, both those with new, untarnished surfaces and those with colorful patinas, offer the artist and the designer an amazing palette of color to choose from and design with. Oxide colors will be predictable to a point, but beyond that it is nature that will take over the design. These colors will also act as potent inhibitors of corrosion. But note that both natural, untarnished surfaces and beautiful patinas on art and architecture forms will require something additional—either in the form of a coating or in the form of energy applied from an elbow—to keep them looking good.

I have worked with copper and many of its alloys for decades. I have hammered it, cut it, welded it, and shaped it into beautiful pieces of art. I have experimented with creating color on the surface of the metal with chemical interaction, heat, and selective electroplating. I have worked with friends to cast it and I have formed its sheets to create incredible surfaces.

Copper is special for its amazing ability to be shaped and stretched and for its ability to react with other elements and compounds to achieve a unique and beautiful surface.

Copper can be cast into glass, and the glass accepts it. It can be severely shaped, and it yields to take the new shape. It can withstand the attack of powerful acids and bases, all the while forming a natural mineral surface that slows further reaction while giving a beautiful patina.

This is the third in a series of books on metals used in art and architecture. I have attempted to cover many of the copper alloys that have found their way into use in art and architecture. New and innovative uses of the metal, along with advances in fabrication techniques and a renewed interest in patination, are fueling a renaissance in the use of copper alloys.

It is the surface of copper alloys—the part that interacts with the environment and the part that absorbs and reflects light in unique and special ways—that we find interesting as a material of design. But industry is also looking for ways of capitalizing on the antimicrobial benefits of the copper alloy surface. Tests have proven bacteria and viruses do not thrive and will diminish when in proximity to copper ions.

The corrosion resistant behavior of the copper alloy surface is unmatched. Few corrosive materials can get through the protective behavior of the oxide surface. All of this is an important and essential quality of the metal, but it is the unique color that draws us to it. There is no other metal that comes close to the intense beauty of copper alloys.

The early alchemists associated each of seven metals with a planet. Copper, one of the oldest metals known to man, was associated with the planet Venus, one of ancient man's “wandering stars.” Copper was thought to represent the characteristics of feminine beauty, caring and nurturing, love and lust.

The symbol for copper is the female symbol that is also the symbol for the planet Venus.

The book is intended to give the artist and designer more knowledge about copper, its alloys and this amazing surface. Those who are interested in the metal will acquire information on how to work with the different copper alloys, how they will interact with the environment with time and exposure. Copper and copper alloys have a vast history, but the story is far from over.

CHAPTER 1Introduction—Element 29

Copper and Copper Alloys

Cu—Cuprum

INTRODUCTION

Of the metals, only copper and gold possess colors other than gray or silver in their natural forms. When copper is combined with different elements, elegant colors and tones can be produced both naturally and artificially. This is the reason why our ancient ancestors first worked with this metal: they could identify it among rocks and stones more easily and it was more abundant than gold. The brightly colored ores of copper, malachite, and azurite surely attracted the attention of early humans. These were not your normal rocks.

Copper is element 29 in the periodic table (Figure 1.1). It falls between element 28 (nickel) and element 30 (zinc). Copper is in the same group as silver and gold: metals that it mixes with and that possess similar properties of electrical and thermal conductivity. Like copper, gold and silver were also highly valued by early man. Being more abundant, copper took on the heaviest workload. The age named for it marks an advance in civilization.

Copper possesses a face‐centered cubic structure in its pure state, but this structure changes as alloying elements are added (Figure 1.2). This face‐centered structure is shared with many other metals, such as aluminum and iron.

The atomic makeup of copper is responsible for many of the unique attributes this metal offers (Figure 1.3). The atomic number of 29 means that copper has 29 protons in the nucleus with 29 electrons making up its outer shells. It is the lone electron in its fourth orbital that gives copper one of its most important traits. This electron is free to move about, allowing electrical current to move easily from atom to atom.

FIGURE 1.1 Copper's position in the periodic table of elements.

FIGURE 1.2 Face‐centered cubic structure of a copper crystal.

FIGURE 1.3 Copper atom.

This lower resistance coming from a single electron in the outer orbit gives copper its exceptional ability to transport electricity. The metals whose atoms have the fewest electrons in their outer (or valence) shell offer the least resistance to the movement of electricity from one atom to the next. Gold, silver, and copper are metals that have only one electron in their valence shells, which gives them their ability to conduct electrical current more efficiently than atoms with more than one electron. This lone electron moves freely around and through the lattice structure of the metal, transferring the electrical current with little resistance. Aluminum has three electrons in its valence orbit, while zinc, nickel, iron, and titanium have two (Table 1.1).

Operating under a principle similar to electrical conductivity, the conductivity of heat has the same order across metals. Alloying will change the heat conductivity of a particular metal, as it does the electrical conductivity. For instance, most bronze alloys of copper will not conduct as well as many aluminum alloys. The alloying elements in bronze diminish its ability to move an electrical charge.

As they are essentially shared, these valence electrons are free to flow in and around the atoms, creating a “sea” of charged particles. This sea of electrons allows the charge to move rapidly and with little resistance as energy is transferred from electron to electron that collectively make up the sea around the copper atoms (Figure 1.4).

Most of the copper found on the Earth's surface is from hydrothermal activity that brought the metal to or near the surface. Other surface copper is drift copper, deposited by glacier activity and randomly set in rubble. Copper makes up approximately 0.0068% of the upper mineral crust of the Earth and is widely distributed with concentrations in select regions.

Copper has a poor strength‐to‐weight ratio as compared to other metals used in industry. However, copper alloys, such as brass alloys, have a strength‐to‐weight ratio equivalent to stainless steels.

TABLE 1.1 Electrical conductivity of various metals in siemens m−1 at 20 °C.

Metal

Siemens m

−1

Silver

6.30 × 10

7

Copper

5.98 × 10

7

Gold

4.52 × 10

7

Aluminum

3.50 × 10

7

Zinc

1.68 × 10

7

Nickel

1.43 × 10

7

Iron

1.04 × 10

7

Titanium

1.80 × 10

6

FIGURE 1.4 Sea of shared electrons around the metal atoms of copper.

Other characteristics of copper include excellent ductility, a deep forming ability, high fracture toughness, high elasticity (resiliency under shock loading), and soft edges.

Copper is also nontoxic—although copper salts are considered ecotoxic in certain instances—and has superior corrosion resistance in many natural environments.

Copper: Element 29

Atomic number 29

Crystal structure

Face‐centered cube

Main mineral source

Chalcopyrite and chalcocite

Color

Salmon red

Oxide

Brown to black

Density

8960 kg/m

−3

Specific gravity

8.8

Melting point

1083 °C

Thermal conductivity

401 W/m

−1

 °C

Coefficient of linear expansion

16 × 10

−6

/°C

Electrical conductivity

100% IACS

Modulus of elasticity

110 GPa

Finishes

Mill specular and nonspecular

Polished satin and mirror

Glass bead

Copper can be painted but this is rarely done.

Porcelain enamel is an art process used extensively on copper.

Plating with other metals such as silver, nickel, and gold is easily accomplished on copper

Artificial patina

Greens, browns, yellows, reds, blacks, and combinations are achievable on copper and copper alloys; the development of chemical patinas on the surface of copper alloys is unmatched in any other metal

Bright appearance

Copper absorbs and reflects the red end of the visible spectrum; alloys alter this reflection by emitting yellow wavelengths along with the red end of the visible spectrum

Reflectance

of ultraviolet

Very good

of infrared

Poor; copper absorbs infrared wavelengths

Relative cost

Medium

Strengthening

Cold working is the main method used to strengthen copper and copper alloys

Recyclability

Very easily recycled; recycled copper and copper alloys retain a high value

Welding and joining

Copper and copper alloys can be welded, brazed, and soldered

Casting

Copper and copper alloys are frequently cast in all casting methodologies

Plating

Copper and copper alloys can be electroplated

Etching and milling

Copper and copper alloys can be etched and chemically milled

IACS = International Annealed Copper Standard; GPa = gigapascal.

COLOR

Another attribute of copper and its alloys is color. There are only two metals that possess a tone other than gray or silver: gold and copper.

When light falls on the metal surface it is intensely absorbed by the atoms at the surface. The electromagnetic wave that we call light only penetrates a very small fractional distance—less than a wavelength—into the metal's surface. But this absorption is intense due to atomic characteristics specific to metals and the electrons that make up the sea that flow around the atoms.

This intense absorption of the electromagnetic wave on the surface causes a pulse of alternating current, which then excites this sea of charged particles and reemits light. This is luster: the intense reflection from a polished metal surface. The smoother the surface is, the greater the reflection. If the surface is coarse, a diffuse reflection occurs. For example, in the case of tarnish—a thickened, diffuse oxide that can develop on the surface of copper—a contrasting darker surface is apparent, dulling the copper's luster. Tarnish is a mineral formation that captures the electrons and makes the metal slightly less conductive.

The color of copper and gold is determined by the makeup of their atoms. When a light wave strikes a copper or gold surface, the portion of the wavelength from 600 to 700 nm is strongly absorbed, as Figure 1.3 shows. In metals, this absorption leads to reemission as reflected light. At the same time, both of these metals absorb the wavelengths at the blue and violet end of the spectrum poorly. This gives copper a reddish color and gold a yellowish color. It is this significant drop‐off in absorption—strong on one end of the spectrum and weak on the other end—that gives these metals their characteristic color.

For example, iron absorbs the wavelengths associated with blue and violet much more than copper, but it does not absorb the wavelengths associated with red, orange, and yellow. It has a fairly flat absorption line across all the wavelengths.1 Stainless steel is similar to iron's reflectivity, but the added chromium increases the reflection of portions of the light wave over 60%. Stainless steel is said to reflect, on average, 60% of the light wave (Figure 1.5).

FIGURE 1.5 Reflectivity of aluminum, silver, stainless steel, copper, and gold.

Source: Data plotted from NASA Technical Note D‐5353, “Solar Absorptances and Spectral Reflectances of 12 Metals for Temperatures Ranging from 300 to 500 K.”

COLORS OF ALLOYS

The color of copper alloys is determined by several factors. The addition of various alloying constituents influences the color up to the point at which the crystal structure of the metal changes. When this occurs, the density and form of the crystal changes and light absorption can potentially change as well.

For example, as zinc is added to molten copper it dissolves and integrates into a single crystal structure, or phase, along with the copper atoms. The alloy becomes progressively more yellow in color. At the point at which 35% zinc is alloyed with copper, the metal reaches a saturation point and the color will be yellow. This is the alloy C27000, also known as yellow brass. As zinc is added beyond this 35% level, a phase change occurs in the crystal makeup, the yellow color loses intensity, and the color goes back to a bronze tone. The copper crystal lattice can no longer take the zinc atoms in and two phases develop: an alpha phase, with a face‐centered cubic structure, and a beta phase, with a body‐centered structure. For example, alloy C28000, commonly known as Muntz metal, contains 40% zinc and is less yellow. Both alpha and beta grains are apparent in alloy C28000 (see Figure 1.6 for comparisons of the natural colors of copper alloys).

Mechanical characteristics also change as alloying constituents are added. As zinc is added, brass alloys get stronger. However, their corrosion resistance, particularly to the condition known as dezincification, will decrease. Once the dual phase appears in the alloy, which occurs at around 40% zinc, cold working ability declines. The C28000 alloy is harder to cold work than alloys with less zinc.

Copper and its alloys have the ability to create amazing colors when they combine with nonmetal elements such as sulfur, chlorine, carbon, and oxygen (Figure 1.7). Almost everyone is familiar with the beautiful patinas that are apparent on copper roofs built a century ago. These attractive, natural‐looking green surfaces developed over time and with exposure to the atmosphere. They were not precolored but allowed to absorb the carbon, sulfur, and chlorine from the air. In a real sense, copper captures the industrial pollutants of sulfur and carbon dioxide from the air and forms these beautiful surfaces composed of copper sulfate, copper chlorides, and copper carbonates.

For instance, the green patina adorning the roofs of many centuries‐old buildings in cities around the world is a form of the mineral brochantite. This mineral has the formula Cu4SO4(OH)6 and displays the characteristic color of pale green. The copper began as a bright salmon‐red color, but as it was exposed to the air, natural humidity, and rain the copper combined with the sulfur and formed the mineral on the surface (Figure 1.8).

FIGURE 1.6 Image of different alloys and colors.

FIGURE 1.7 Color changes in brass alloys.

The patina is the copper surface corroding, but the difference is that once formed, this tightly adhered compound protects the underlying metal. The rate of corrosion slows way down as this inert, mineral form of copper achieves a level of equilibrium with the surrounding environment.

The Statue of Liberty (Figure 1.9) initially had the color of a penny when delivered. It was not polished copper but had the rich copper color of a slightly aged penny. Dedicated in 1886, it was subject to years of exposure to the polluted environment of industrial New York in the later part of the 1800s and early 1900s. Exposed to both the chloride‐rich seaside and pollution from heavy industry on the East Coast, the green patina we see today formed. As the inert mineral layer of brochantite, antlerite, and atacamite that made up the patina formed, it protected the copper plates from degradation.2

FIGURE 1.8 A naturally formed patina.

FIGURE 1.9 The Statue of Liberty.

FIGURE 1.10Perseus with the Head of Medusa, by Benvenuto Cellini.

In the world of art, this natural oxidation is a sign that the metal is corroding. Bronze statues and copper alloy artifacts must be protected, or the surfaces will corrode to some degree and can be visually affected as the surface metal combines to form the various corrosion salts. Sculpture, if not maintained, will oxidize and develop a patina. In severe cases, particularly in chloride environments, the copper alloy can undergo a destructive corrosion condition known as “bronze disease.” However, one only has to look at the ancient sculptures that have been residing under the sea for centuries to observe that they may have corrosion products, but they are still intact and recognizable.

When some maintenance is performed, bronze sculptures can last centuries and appear as if they were cast in recent times. Figure 1.10 shows the famous sculpture Perseus with the Head of Medusa, created by Benvenuto Cellini around 1550 and located in the Loggia dei Lanzi in Florence, Italy. One of the most intricate and beautiful cast sculptures in existence, it stands at 5.2 m (approximately 18 ft.) as measured from the stone base to the top of Medusa's head. This remarkable, nearly 500‐year‐old sculpture is well maintained.

COPPER MINERALS

Copper and the brass and bronze alloys of copper are metals that have been with mankind since antiquity. Gold, silver, platinum, and copper are the only metals found in their native state. Copper, being less rare and occasionally found on the surface, was more available to early man. When the nature of the material was discovered and disseminated by our early ancestors, the Stone Age was over and the Copper Age was upon mankind. Useful tools that could be reused and reshaped originated with the metal copper.

Copper makes up only about 0.007% of the Earth's upper mineral strata. Like iron and nickel it is a denser metal, so one would expect copper to be found deeper in the Earth, as lighter elements such as silicon and aluminum would be expected to float over heavier elements (Table 1.2).

Primary copper ores are called “porphyry deposits.” These ores are the virgin, nonrecycled sources of copper. They flow during magma releases but they often combine with sulfur to form heavy copper and iron sulfides, such as the minerals chalcopyrite (CuFeS2), a mineral composed of copper, iron, and sulfur, and bornite (Cu2FeS4). Most copper is miles below the surface of the Earth. As the Earth was formed these heavier metals sank, leaving a surface with very little copper. These heavy compounds tended to sink deeper in the fluid flows and were then expelled in magma during an eruption.3 This occurred in the Rocky Mountain region in the United States and in the formation of the Andes in South America.

Both of these regions are areas where large deposits of copper minerals are still being mined. Similar regions where volcanic activity over the eons moved minerals onto the surface of the planet exist around the world; places such as Papua province, where the Sudirman Mountains are located, and the southern Congo are rich in porphyry mineral deposits.

TABLE 1.2 Approximate percentages of elements in the Earth's upper mineral strata.

Element

Percentage (%)

Oxygen

46

Silicon

27

Aluminum

 8.1  

Iron

 6.3  

Nickel

 0.009

Zinc

 0.008

Copper

 0.007

TABLE 1.3 Mineral forms of copper.

Common mineral name

Formula

Color

Cuprite

Cu

2

O

Red oxide

Tenorite

CuO

Black

Malachite

CuCO

3

(OH)

2

Intense green with banding

Pseudomalachite

Cu

5

(PO

4

)

2

(OH)

4

Emerald green

Azurite

Cu

3

(CO

3

)

2

(OH)

2

Intense blue

Bornite

Cu

5

FeS

4

Dark red with slight iridescence

Chalcocite

CuS

Black or black gray

Brochantite

Cu

4

SO

4

(OH)

6

Green

Antlerite

Cu

3

SO

4

(OH)

6

Green

Nantokite

CuCl

Pale green

Atacamite

Cu

2

(OH)

3

Cl

Crystalline green

The mineral form of a metal is more stable and slow to change. When exposed to the atmosphere copper and its alloys can develop an oxide layer that approaches one of the more common mineral forms of copper. Cuprite, for instance, forms on exposed copper alloy surfaces when subjected to heat and humidity. Nantokite with atacamite can form on copper alloys exposed to chlorides when near the sea (Table 1.3).

Bronze sculptures that have been exposed to the environment for a long period of time can form several of these mineral compounds, which can appear as spots or streaks on the surface of the original patina provided by the foundry (Figure 1.11).

HISTORY

The distinctive color copper possesses differentiates it from other natural minerals. The occasional pure native form of the metal would have attracted early man to this heavy, dense rock—a rock that would not fracture but that would yield to blows and take a different shape. Its weight and malleable nature made copper a useful discovery, and because of these attributes early man probably collected it when he came across it.

Easily recognizable by its color and tactile nature, the substance would have aroused the inquisitive nature of early humans. The surface of native copper allowed early man to shape it by hammering it with stone or wood. Initial hammering was probably performed using round stones or shaped logs, after which the substance was hammered into wooden forms. The plasticity of the metal would have been like no other material known. Forms of copper, cold hammered into jewelry, weapons, and tools, have been found in Anatolia dating back to 9000 BCE. Skills used in making clay pottery, developed prior to the Copper Age, would have been adapted to this metal, although more force would have been needed and harder materials necessary to shape the copper into a useful form.

FIGURE 1.11 Various minerals of copper.

Once someone found that you could soften the metal further by heating it, these lumps of copper could be flattened to platelike forms, even blades. As hammering is repeated on the copper form it thins out as it is being shaped and the worked metal hardens, losing some of its elasticity. An edge can be sharpened on coarse rocks, making a blade form that can act as a tool or a weapon. A copper edge is short‐lived, but the utility it would have offered and the ease of working the metal would have made copper an important early material.

Every early civilization used copper in art and decoration. From the Sumerians and Chaldeans in Mesopotamia, across Egypt, to present‐day Turkey and on to India, copper was a part of early civilizations dating back nearly to 8000 BC. We know this by the character of the metal itself and its corrosion resistance. Artifacts made from copper exhibit only minor decay, even after all these centuries (Figure 1.12).

In the Upper Peninsula of Michigan on the shores of Lake Superior, in the area known as Keweenaw, ancient copper mines have been found along with copper tools.4 Thought to date back as far as 4000 BC, these ancient mines show that people dug shallow mines in search of copper. Large copper boulders and mile‐long veins were intermixed with general rock and rubble in this region. High‐purity copper lumps were intermixed with the rubble on or near the surface. Surface copper, sometimes referred to as “drift copper,” was deposited by the receding glaciers. These early inhabitants had no available means of cutting the large chunks of metal down, so they gathered the smaller, more manageable portions and left the large sections with some of their broken tools. Early Native Americans are believed to have ventured yearly to this site to gather copper to make ornamentation and other items. Old stone hammers and axes have been found where these early inhabitants attempted to carve off sections they could transport back to their villages. Some sections were simply too massive to transport. You can see one of the larger boulders of nearly pure copper, called the Ontonagon Boulder, in the Smithsonian's National Museum of Natural History. This large boulder weighs in at 1682 kg (3708 lb.). The Keweenaw Indians claimed it as a sacred object and they sought its return.5 This boulder was one of the “proofs” given in 1843 for starting the mineral rush to the Upper Peninsula region of Michigan (Figure 1.13).

FIGURE 1.12 Approximate time periods of major copper activity in ancient times.

This region of the United States was invaluable in bringing America into the Industrial Revolution. It was the first site of a mad rush for mineral wealth and preceded the California Gold Rush by a number of years. From the early 1800s and for nearly the next 150 years, copper was heavily mined in this region. More than 6 billion kg are said to have been mined during this time. Artifacts have been recovered from these and other ancient civilizations still intact, demonstrating the diverse uses this metal was put to by early mankind.

FIGURE 1.13 Image of the Ontonagon copper boulder.

Source: Wikimedia Commons; public domain.

The ductile nature of copper was one of the first characteristics of the metal that early man was able to use to his advantage. Copper was hammered thin and used in crude water‐piping systems in early Egypt, the Romans used thin plates of copper to clad the roof of structures such as the Pantheon, and helmets and shields were created by artisans familiar with working with this pliable metal (Figure 1.14).

FIGURE 1.14 Roman helmets made from copper.

Early Egypt made extensive use of copper and copper alloys. Those in the ruling classes of Egypt used handmade mirrors of copper; small, thin razors of copper; and even colorful makeup made from mixtures derived from the copper ores of malachite and azurite. As far back as 3500 BC the Egyptians learned to mix alloying elements with copper to modify its color and improve specific properties. Copper mixed with tin melts at around 913 °C, while unalloyed copper requires a temperature of 1083 °C to melt. The Egyptians realized they could cast the molten metal into molds by adding specific amounts of tin. The lost‐wax casting method was developed, and casting of intricate forms came into use along with purposeful alloying of metals.6 For example, bronze is harder than copper; although this lack of ductility makes shaping bronze difficult, its hardness and durability allows it to hold an edge better than softer copper.

The Pyramid of Khufu in Giza (also known as the Great Pyramid of Giza), constructed around 2560 BC, is made from over 2,300,000 massive blocks of stone. The stones were cut using copper alloy tools that could be reformed and reused.

Some of the earliest copper mines were in Cyprus. The word “copper” originates from the Latin word cuprum, which itself is a contraction of a Latin term meaning “the metal of Cyprus” and which references the extensive mines found on the island. The metal became a significant source of trade in the region of the eastern Mediterranean.

On the Adriatic coast of Italy, down in the “bootheel,” is the city of Brindisi, which was known for bronze trade and for bronze casting in ancient times. The Latin term es Brundisium (“from Brindisi”) is thought to be the root of the word “bronze”—but the amount of trade in copper and copper alloys in this region attests to the importance of copper.

The Colossus of Rhodes, one of the Seven Wonders of the World described in classical antiquity, was made of bronze. This statue of the Greek god Helios was cast in bronze and erected over the entry to the port of Rhodes. It stood more than 32 m in height. Unfortunately, it collapsed during an earthquake in 226 BC. Nothing remains of it today other than the description.

Given the value of the metal and the technology to remelt cast objects and recast them, many bronzes of the Greek and Roman period were taken and repurposed. One can see the many pedestals where they once stood when visiting the ancient sites of Rome and Greece.

In Nepal the Pashupatinath Temple was built around the fifth century to honor the Lord Pashupatinath, an incarnation of the Hindu god Shiva. The temple, located on the riverbank in Kathmandu and sometimes referred to as the “copper temple,” was decorated with copper ornamentation when it was built. Today it is clad in modern forms of copper.

Copper alloys have always played a part in cladding and adorning religious buildings in a variety of civilizations. In Japan, the Todaiji Temple is home to a massive cast Buddha. In the eighteenth century, over 400 tons of cast bronze was used to produce this 15‐meter‐tall Buddha (Figure 1.15).

FIGURE 1.15 Giant cast Buddha at the Todaiji Temple in Japan.

In many Christian churches the use of copper alloys is prevalent. Candleholders, baptismal fonts, and many other polished brass religious totemic items adorn churches and synagogues (Figure 1.16). Church roofs and steeples are commonly clad in thin skins of copper and have been since the technology for rolling thin sheets of the metal were introduced. The metal's resistance to environmental change and its perception as an elegant and special material make it ideal for surfacing roofs of churches.