Metals Used in Metal Sculpture

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Metals Used in Metal Sculpture

Summary:

The oldest metal sculpture pieces are made out of copper alloys and bronze. These metals offer the artist strength while also being malleable. Other metals such as gold and silver are softer, enabling the artisan the ability to shape the metal with tools and by hammering.  Related to the sculpting process is metal casting, where metals can be poured into a mold.

It is thought that metal casting as an ancient art dates back 6000 years with the first works made out of gold and copper.

Ancient civilizations such as the Egyptians carved deities and leaders in gold and other precious metals.They were also expert at “lost wax” casting which allowed small intricate shapes to be cast.

The Chinese used metal to honor symbols of importance such as tigers, religious figures and leaders.

The use of metal continued with the Greeks and Romans, who used bronze to make life-like statues and figurines.

Once the Roman empire fell the baton was passed to Charlemagne and the germanic tribes. This “father of Europe” rule during Medieval times. He oversaw the use of bronze and iron to commemorate his rule. Statues were also made of the Virgin Mary and Jesus.

During the Renaissance art was a front and center part of the culture. Statues were produced made out of copper and bronze that were either commissioned by the Catholic Church (statues of saints) or of leaders.

In modern times, such as metal sculpture found in the United States, are used to commemorate war heroes (solider on horse) as well as a place in the avant-garde art scene.  Large metal sculptures are also a fixture in parks and prominent public spaces.

Cloud Gate

Stainless Steel Statue Art Installation by Indian-born British artist Anish Kapoor. Located in Chicago’s Millennium Park.

Welding and Metal Sculpture Video

Kits and Sculpture Supplies

Aluminum Sculpture Kit

Shown: OWI Rhino Beetle Aluminum Skulpture Kit

There are many metal sculpture kits available that are perfect for the hobbyist or artist just getting started. These can often be purchased for under $20 (U.S.) and are relatively easy to assemble.

Metals Used in Sculpture

Bronze

John VIII Palaeologus Medal

Thought to be the first portrait medal of the Renaissance era. The revers image is the emperor on horseback. Produced out of cast bronze and other metals between 1438 and 1439.
Source: Wikipedia, Fasanelli, J. A., (1965) ‘Some Notes on Pisanello and the Council of Florence’, Master Drawings, vol.3, no.1 pp. 36–47

The introduction of bronze was significant to any civilization
which encountered it. Metal sculpture, tools, weapons and armor made of bronze were
harder and more durable than their stone and copper ("Chalcolithic")
predecessors. In early use, the natural impurity arsenic sometimes
created a superior natural alloy; this is termed arsenical bronze.

While copper and tin can naturally co-occur, the two ores are
rarely found together (although one ancient site in Thailand provides a
counterexample). Serious bronze work has therefore always involved
trade. (In fact, archaeologists suspect that a serious disruption of the
tin trade precipitated the transition to the Iron Age.) For Europe, the
major source for tin was Great Britain.

The earliest tin-alloy bronzes date to the late 4th millennium BC
in Susa (Iran) and some ancient sites in Luristan (Iran) and
Mesopotamia.

Bronze was stronger than the era's iron; quality steels were not
available until thousands of years later. But the Bronze Age gave way to
the Iron Age, perhaps because the shipping of tin around the
Mediterranean (or from Great Britain) became more limited during the
major population migrations around 1200 – 1100 BC, which dramatically
limited supplies and raised prices. Bronze was still used during the
Iron Age, but for many purposes the weaker iron was found to be
sufficiently strong. As iron working improved, iron became both cheaper
and stronger, eclipsing bronze in Europe by the early to mid-Middle
Ages.

Thomas Jefferson Memorial Sculpture in Bronze

"Thomas Jefferson Memorial Sculpture Dome" by Jamieadams99 - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons

Properties

When steel is excluded from the discussion, bronze is superior to
iron in nearly every application. While it develops a patina, it does
not oxidize. It is considerably less brittle than iron and has a lower
casting temperature. (Steel, of course, has wonderful properties that
bronze cannot compete with.)

Copper-based alloys have lower melting points than steel and are more
readily produced from their constituent metals. They are generally
about 10 percent heavier than steel, although alloys using aluminium or
silicon may be slightly less dense. Bronzes are softer and weaker than
steel, and more elastic, though bronze springs are less stiff (and so
store less energy) for the same bulk. Bronzes resist corrosion
(especially seawater corrosion) and metal fatigue better than steel.
Bronzes also conduct heat and electricity better than most steels. The
cost of copper-base alloys is generally higher than that of steels but
lower than that of nickel-base alloys.

Copper and its alloys have a huge variety of uses that reflect
their versatile physical, mechanical, and chemical properties. Some
common examples are the high electrical conductivity of pure copper, the
excellent deep-drawing qualities of cartridge case brass, the
low-friction properties of bearing bronze, the resonant qualities of
bell bronze, and the resistance to corrosion by sea water of several
bronze alloys.

In the twentieth century, silicon was introduced as the primary
alloying element, creating an alloy with wide application in industry
and the major form used in contemporary statuary. Aluminium is also used
for the structural metal Aluminium bronze.

Bronze is the most popular metal for top-quality bells and
cymbals, and, more recently, saxophones. Bronze is also widely used for
cast metal sculpture (see bronze sculpture). Common bronze alloys often
have the unusual and very desirable property of expanding slightly just
before they set, thus filling in the finest details of a mould.

Bronze also has very little metal-on-metal friction, which made
it invaluable for the building of cannon where iron cannonballs would
otherwise stick in the barrel. Bronze is still widely used today for
springs, bearings, bushings and similar fittings, and is particularly
common in the bearings of small electric motors. Phosphor bronze is
particularly suited to precision-grade bearings and springs.

Bronze is typically 60% copper and 40% tin. Alpha bronze consists
of the alpha solid solution of tin in copper. Alpha bronze alloys of
4-5% tin are used to make coins, springs, turbines and blades.

Commercial bronze (otherwise known as brass) is 90% copper and
10% zinc, and contains no tin. It is somewhat stronger than copper and
it has equivalent ductility. It is used for screws and wires

Brass

Cyparissus

Cyparissus', copper and brass sculpture by Bumpei Akaji, 1968, Hawaii State Art Museum". Via Wikipedia

Brass is the term used for alloys of copper and zinc in a solid solution.

Typically it is more than 50% copper and from 5 to 20% zinc, in comparison to bronze which is principally an alloy of copper and tin.. Despite this distinction, some types of brasses are called bronzes.

Brass has a yellow color, somewhat similar to gold. Because of this,
and its relative resistance to tarnishing, it is often used as a
decoration.

Brass has been known to man since prehistoric times, long before zinc
itself was discovered. It was produced by melting copper together with
calamine, a zinc ore. During this process, the zinc is extracted from
the calamine and instantly mixes with the copper. Pure zinc, on the
other hand, is too reactive to be produced by ancient metalworking
techniques.

Properties

The malleability and acoustic properties of brass have made it the
metal of choice for brass musical instruments such as the tuba. Higher
malleability than copper and zinc.

In some environments, brasses with higher content of zinc are prone
to a selective leaching corrosion known as dezincification. In some
territories, plumbing fittings designed to resist dezincification are
embossed "CR" (corrosion resistant). A dezincified fitting has the pink
appearance of pure copper and will easily crumble, being reduced to a
weak sponge-like matrix. Brass is a versatile manufacturing material
because of its hardness and workability.

Cast Iron

Cherkes and a Woman On Horse

Kaslinskoe cast iron casting metal sculpture. "Radishchev Art Museum 10" by Eugene Alexandrovich Lanceray - Self-photographed. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons

Cast iron usually refers to grey cast
iron, but can mean any of a group of iron-based alloys containing more
than 2% carbon (alloys with less carbon are carbon steel by definition).

It is made by remelting pig iron, often
along with substantial quantities of scrap iron and scrap steel, and
taking various steps to remove undesirable contaminants such as
phosphorus and sulfur, which weaken the material. Carbon and silicon
content are reduced to the desired levels, which may be anywhere from 2%
to 3.5% for carbon and 1% to 3% for silicon depending on the
application. Other elements are then added to the melt before the final
form is produced by casting.

The iron-carbon eutectic point lies at 1403 kelvins and 4.3 mass %
carbon. Since cast iron has nearly this composition, its melting
temperature of 1420 to 1470 K is about 300 K lower than the melting
point of pure iron. Cast iron tends to be brittle, unless the name of
the particular alloy suggests otherwise. The color of a fracture surface
can be used to identify an alloy: carbide impurities allow cracks to
pass straight through, resulting in a smooth, "white" surface,
while graphite flakes deflect a passing crack and initiate countless new
cracks as the material breaks, resulting in a rough surface that
appears grey.

Gray Cast Iron

Gray cast iron (also called Gray Iron or International Standard A48) is a type of cast iron, with the difference being that is has what is called a graphitic microstructure. As the name implies, it is named after its' color, which it inherits from the graphite content.

Silicon is essential to making of grey cast iron
as opposed to white cast iron. Silicon causes the carbon to rapidly
come out of solution as graphite, leaving a matrix of relatively pure,
soft iron. Weak bonding between planes of graphite lead to a high
activation energy for growth in that direction, resulting in thin, round
flakes. This structure has several useful properties such as good machinability.

Copper

Statue of Liberty

"Statue of Liberty 7" Clad in Copper Sheeting by Elcobbola - Own work. Licensed under Public domain via Wikimedia Commons

Copper is a chemical element in the periodic table that has the symbol Cu (L.: Cuprum) and atomic number 29.

It is a ductile metal with excellent
electrical conductivity, and finds extensive use as a building material,
as an electrical conductor, and as a component of various alloys.

Notable Characteristics

Copper is a reddish-colored metal, with a high electrical and thermal
conductivity (among pure metals at room temperature, only silver has a
higher electrical conductivity). Copper has its characteristic color
because it reflects red and orange light and absorbs other frequencies
in the visible spectrum, due to its band structure. Contrast this with
the optical properties of silver, gold and aluminium.

Copper is insoluble in water (H2O) as well as isopropanol, or isopropyl alcohol.

There are two stable isotopes, 63Cu and 65Cu,
along with a couple of dozen radioisotopes. The vast majority of
radioisotopes have half lives on the order of minutes or less; the
longest lived, 64Cu, has a half life of 12.7 hours, with two decay modes, leading to two separate products.

There are numerous alloys of copper—speculum metal is a copper/tin
alloy, brass is a copper/zinc alloy, and bronze is a copper/tin alloy.
Monel metal is a copper/nickel alloy, also called cupronickel.

Copper Bull Sculpture

"British Museum Copper Bull" by BabelStone (Own work). Licensed under Creative Commons Zero, Public Domain Dedication via Wikimedia Commons

Gold

Gold Sculpture Musica Raft

"Muisca raft Legend of El Dorado Offerings of gold" by Andrew Bertram - World66. Licensed under Creative Commons Attribution-Share Alike 1.0 via Wikimedia Commons

Gold is a chemical element in the periodic table that has the symbol Au (from the Latin aurum) and atomic number 79.

A soft, shiny, yellow, dense, malleable,
ductile (trivalent and univalent) transition metal, gold does not react
with most chemicals but is attacked by chlorine, fluorine and aqua
regia. The metal occurs as nuggets or grains in rocks and in alluvial
deposits and is one of the coinage metals.

For millennia gold has been used as money, a store of value and in
jewelry. Modern industrial uses include dentistry and electronics. Gold
forms the basis for a monetary standard used by the International
Monetary Fund (IMF) and the Bank for International Settlements (BIS).
Its ISO currency code is XAU.

Notable Characteristics

Gold is a metallic element with a characteristic yellow color, but
can also be black or ruby when finely divided, while colloidal solutions
are intensely colored and often purple. These colors are the result of
gold's plasmon frequency lying in the visible range, which causes red
and yellow light to be reflected, and blue light to be absorbed. Only
silver colloids exhibit the same interactions with light, albeit at a
shorter frequency, making silver colloids yellow in color.

Tin

Tin Man Sculpture

Tin Man Metal Sculpture Made From Cookware such as Pots and Pans

Tin is a chemical element in the periodic table that has the symbol Sn (L. Stannum) and atomic number 50.

This silvery, malleable poor metal that is
not easily oxidized in air and resists corrosion is found in many alloys
and is used to coat other metals to prevent corrosion. Tin is obtained
chiefly from the mineral cassiterite, where it occurs as an oxide.

Notable Characteristics

Tin is a malleable, ductile, highly crystalline, silvery-white metal
whose crystal structure causes a strange screeching sound known as the
"tin cry" when a bar of tin is bent (caused by crystals breaking). This
metal resists corrosion from distilled sea and soft tap water, but can
be attacked by strong acids, alkalis, and by acid salts. Tin acts as a
catalyst when oxygen is in solution and helps accelerate chemical
attack.

Tin forms the dioxide SnO2 when it is heated in the presence of air. SnO2, in turn, is feebly acidic and forms stannate (SnO3-2)
salts with basic oxides. Tin can be highly polished and is used as a
protective coat for other metals in order to prevent corrosion or other
chemical action.

Because is it so malleable, it is a popular choice in metal structure.

Wrought Iron

Wrought Iron Lawn Statue

"IITB Lawn" Metal Sculpture by Rohan Sethi, IIT Bombay - Personal communication. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons

Wrought iron is a very pure form of
commercial iron, having a very small carbon content. It is tough,
malleable, ductile and can be easily welded. However, it is too soft to
make blades and swords. When formed into bars, it is known as "bar
iron".

Wrought iron has been used for thousands of years, and represents the "iron" that is referred to throughout history.  In turn, it is also in the metal sculpture.

Wrought iron was originally produced by a variety of methods today
known as a bloomery. Bloomeries used charcoal-heated smelters, typically
in the form of small pots or ladles, into which the ore was poured and
then covered with a thin layer of charcoal. Air was blown onto the
charcoal after lighting it on fire. The heat produced would melt the
ore. As the ore melted it would be reduced (ore is iron oxide, or rust),
mixing with the charcoal to release carbon dioxide. This way little
carbon entered the iron directly.

In a bloomery, the fire does not get hot enough to melt the iron
completely, so you are left with a spongy mass containing iron and
silicates from the ore; this is iron bloom from which the technique gets
its name. The bloom was then mechanically worked to break off the
masses of slag and impurities. This process gives rise to the name
"wrought", as the iron was pounded, twisted, and folded. As a result of
this process, many strands of slag are mixed into the metal. These slag
inclusions give it a "grain" like wood, and distinct look when etched.
Also due to the slag, it has a fibrous look when broken or bent past its
failure point.

Silver

Silver Sculpture of Standing Buddha Under a Parasol

"British Museum Asia 8" by Gryffindor - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons

Silver is a chemical element with the symbol Ag (from the traditional abbreviation for the Latin argentum).
A soft white lustrous transition metal, it has the highest electrical
and thermal conductivity of any metal and occurs in minerals and in free
form.

This metal is used in metal sculpture, coins, jewelry, tableware, photography, and in mirrors.

Notable Characteristics

Silver is a very ductile and malleable (slightly harder than gold)

For Additional Reading

Gold Museum