Repoussé and chasing

Repoussé is a metalworking technique in which a malleable metal is shaped by hammering from the reverse side to create a design in low relief. Chasing or embossing is a similar technique in which the piece is hammered on the front side, sinking the metal. The two techniques are often used in conjunction.

Many metals can be used for chasing and repoussé work, including gold, silver, copper, and alloys such as steel, bronze, and pewter.

These techniques are very ancient and have been extensively used all over the world, as they require only the simplest tools and materials, and yet allow great diversity of expression. They are also relatively economical, since there is no loss or waste of metal, which mostly retains its original size and thickness. Toolmarks are often intentionally left visible in the result.

A few among many famous examples of repoussé and chasing are the prehistoric Gundestrup cauldron, the mask on the mummy of Tutankhamun, the body armours of the Bronze Age, the copper ornaments made by the Native Americans in the Southeastern United States, and the Statue of Liberty in New York City.

Etymology

The word repoussé is French and means "pushed up", ultimately from Latin pulsare, which means "to push". Repoussage is the noun to refer to the technique, with repoussé being an adjective referring to a piece to which the technique has been applied (e.g. "repoussé work", "repoussé piece").

Chasing comes from the French word, chasser meaning to drive out, or to chase around which is what the artists are doing as they "chase" the forms on their metal in order to create their final design.

History

The techniques of repoussé and chasing date from Antiquity and have been used widely with gold and silver for fine detailed work and with copper, tin, and bronze for larger sculptures.

European prehistory and Bronze Age

During the 3rd millennium BC, in the Middle East, a variety of semi-mass production methods were introduced to avoid repetitive free-hand work. With the simplest technique, sheet gold could be pressed into designs carved in intaglio in stone, bone, metal or even materials such as jet. The gold could be worked into the designs with wood tools or, more commonly, by hammering a wax or lead "force" over it.

The alternative to pressing gold sheet into a die is to work it over a design in cameo relief. Here the detail would be greater on the back of the final design, so some final chasing from the front was often carried out to sharpen the detail.

The use of patterned punches dates back to the first half of the 2nd millennium BC, if not far earlier. The simplest patterned punches were produced by loops or scrolls of wire.

The Gundestrup cauldron (a product of the Celtic culture, made between 150 BC and 1 AD) had originally thirteen separate silver panels, with repoussé relief, lining the inside and outside of the vessel.

Ancient Egypt

In 1400 BC, the Egyptian Amarna period, resin and mud for repoussé backing was in use.

A fine example of Egyptian repoussé is the mummy mask of Tutankhamun, a Pharaoh of the late Eighteenth Dynasty. The majority of the mask was formed using the technique of repoussé from what appears to be a single sheet of gold. The lapis lazuli and other stones were inlaid in chased areas after the height of the form was completed. The ceremonial beard, Nekhbet vulture, and Uraeus were attached separately.

Classical antiquity

By Hellenistic times, combined punches and dies were in use. In 400 BC, the Greeks were using beeswax for filler in repoussé.

Classical pieces using repoussage and chasing include the bronze Greek armour plates from the 3rd century BC.

The Warren Cup is a Roman silver cup, and the Mildenhall Treasure, the Hoxne Hoard, the Water Newton Treasure and the Berthouville Treasure are examples of hoards of Roman silver found in England and northern France with many pieces using these techniques. Another example piece using this technique is The Stag’s Head Rhyton, dating to around 400 BCE, which is made from a silver sheet and features three scenes of warriors battling, each scene with two warriors.

India

Repoussé and chasing are commonly used in India to create objects such as water vessels. These vessels are generally made using sheets of copper or silver.

Pre-Columbian America

Repoussage and chasing were used by many Pre-Columbian civilizations in the Americas, such as the Chavín culture of Peru (about 900 to 200 BC), to make ornaments of gold and other metals.

During the Hopewell and Mississippian periods of the American Southeast and Midwest goods of repoussé copper were fashioned as ritual regalia and eventually used in prestige burials. Examples have been found with many S.E.C.C. designs such as Bi-lobed arrow motif headdresses and falcon dancer plaques. Although examples have been found in a widely scattered area (Spiro, Oklahoma, Etowah, Georgia, and Moundville, Alabama), most are in what is known as the Braden Style, thought to have originated at the Cahokia Site in Collinsville, Illinois. Several copper workshops discovered during excavations of Mound 34 at Cahokia are the only known Mississippian culture copper workshops.

Modern works

The largest known sculpture created with this technique is the Statue of Liberty, properly Liberté éclairant le monde, ("Liberty Enlightening The World"), in Upper New York Bay. The statue was formed by copper repoussé in sections using wooden structures to shape each piece during the hammering process.

Technology

In terms of working technology, a distinction is made between drawing, deep drawing, bouncing, displacement and compression:

Mounting is done by circular hammering from the center of the workpiece, working in a spiral manner towards the edge.

Deep drawing is the generally industrial process of pressing down a hollow sheet of metal, with the aim of preventing the material from folding. Indentation refers to the manual process of driving a piece of metal into a wooden trough.

Bouncing is used to "dent out" narrow-necked vessels using a special tool, a bouncing iron, i.e. to shape them outwards. Bouncing is an auxiliary method when normal external processing with driving hammers, even in conjunction with punches, is no longer possible, especially when the aim is to drive out narrow-necked hollow objects such as vases, drinking vessels or other plastically deformed workpieces used as industrial prototypes. With bouncing, the blows have an indirect effect. The bouncing iron is set into vibration by blows from a light hammer, which cause a deformation of the workpiece at the rounded end of the iron.

Displacement is often used in both chasing and forging to reduce the material cross-section on a solid base (anvil).

In the process of forging, compression is also called drawing in. The wrinkling or tearing of the materialmust

The sheet metal or solid metal material to be driven out is worked on the back using a driving hammer or forging hammer, and expands in the process. If this is done on a solid surface such as an anvil or driving anvil, a larger section of the sheet metal is deformed into a curve. On a more flexible surface, on the other hand, much finer and more precise work is possible, comparable to deep drawing. To create a relief, the sheet metal to be worked on is placed on lead or putty for further driving out and, if necessary, later chasing. Here, however, the work is started from the front. The processing is carried out using differently shaped driving hammers and punches or with various driving sticks. A driving stick is often used. A driving bag, a leather bag filled with sand or similar material, serves as a base for free-form artistic work. Finer work is achieved by embedding the sheet metal in driving putty and then driving or chasing it using smaller tools.

The metals best suited for hand- hammering are copper and certain copper alloys, so-called wrought alloys, such as soft brass (for example tombac), silver and (for reasons of cost, rarely) gold alloys. In principle, aluminum and stainless steel are also suitable. Bronze and iron sheets, which are naturally harder and therefore more difficult to work, are of course also suitable for hammering. The latter are more commonly found in architectural applications. In earlier times, only the technique of hammering could be used, for example, in the manufacture of vessels or ancient helmets and many other objects. There were no other options for spatially artistic metalworking until the late modern or modern era, which of course also applied to everyday objects such as pots or large cauldrons. The well-known process of casting was generally avoided for reasons of cost.

During the forging process the crystal structure of the metal is disrupted because the deformation through manual or industrial processing (deep drawing) increases the dislocation density and the material work hardens. In this process the metal becomes increasingly harder and more brittle; this is known as work hardening. Annealing the non-ferrous or alloyed precious metal and then cooling it in water between the individual phases of the process restores the original plasticity. This means that forging can be carried out repeatedly until the final shape is achieved. Sometimes, for example in the production of vessels, the workpiece must be hammered after the desired shape has been achieved in order to achieve the desired further hardening for use.

Professions that are still related to the activity today are called: blacksmith, blacksmith, coppersmith, goldsmith, silversmith, tinsmith (also called plumber, which has nothing to do with the colloquial job title for the gas and water fitter), belt maker, etc.

Former, now almost extinct, job titles that have a connection to metalworking: blacksmith, pansmith, boilermaker, weaponsmith, armorer, armorer, tinsmith, tinsmith, redsmith, chainsmith, locksmith, toolsmith, etc.

Many of the requirements for metalworking are now taken over by the metalsmith. The apprenticeship for "metalsmith," which was abolished in the 1980s, is now called "metalworker, specializing in design." However, this profession no longer teaches all the available basic knowledge of metalworking, as was common in previous training as a (...) blacksmith.

Methods

The process of chasing and repoussé requires a number of steps.

Annealing

The metal plate should usually be annealed—that is, heated for some time at a temperature sufficient to reduce its internal stresses—to make it as malleable as possible. This process may have to be repeated several times, as many metals harden and become brittle as they are deformed by the hammering.

Pitch backing

The plate must then be fixed on a suitable support. A commonly used technique is to place the metal over a layer of chasers pitch. The pitch is heated until it is soft enough to make good contact with the metal, filling all its nooks and crannies, and then allowed to cool. At room temperature, the pitch must be hard enough to adhere to the metal and hold it in place, but still soft and plastic enough to "give" as the metal is hammered into it.

The pitch is often cast as a thick layer over some softer backing material that can absorb larger deformations.

The metal plate will have to be released from the pitch several times, for turning it over and/or for re-annealing. Pitch residues stuck to the plate must be removed with an appropriate solvent.

Lining

Once the plate is firmly held by the pitch, front side up, the outline of the desired design is lightly chased ("lined") on it by a special tool (a "liner"), that creates narrow raised lines on the other side.

Repoussé and chasing

The metal is turned over, and firmed again over the pitch, with the back side up. The main repoussé work is then performed, using a variety of punches.

Once the main repoussé is done, the piece is again released by heating. The cavities on the back side, created by the repoussé work, are filled with melted pitch. Once that filling has hardened, the plate is again turned over and placed on top of a layer of softened pitch. Once the pitch has hardened, the design is then refined by chasing. These procedures can be repeated several times, alternating between repoussé and chasing.

Hot forming

Repoussé and chasing can also be done on materials, like steel, that are too hard to be cold-formed by hammering. That is accomplished by heating the piece to a high enough temperature to make it malleable, as in forging. In this case pitch must be dispensed with, or replaced by some material (like sand) that can withstand the heat and provide the right kind of "giving" support.

Tools

The tools needed for these techniques are 

A container for the pitch, such as a "pitch tray" for larger plates, or a heavy hemispherical cast iron "pitch bowl" for smaller ones. The bowl can be placed over a sand bag or leather ring, and tilted to whatever angle is most convenient.

A heat gun or blow torch to soften the pitch in order to fix the plate, or to release it.

A set of "punches", that is, chisels with smooth tips that are used to push the metal:

A "liner" has a flattened tip with a slightly curved blunt edge. It is used to chase narrow grooves in the metal, or to repoussé narrow ridges from the back side; both for outlining the work, and to refine edges in the final object.

A "planisher" has a smooth, flat tip meant for pushing out large, flat areas of metal.

A "doming" or "dotting" tool has a round or oval tip of small to moderate diameter, and can be used to chase dimples or grooves, or repoussé bumps and ridges, of various widths.

A "matting" tool has a pattern cut into the tip, and is used (mainly in chasing) to create textured areas.

A "hollow-faced" punch has a raised contour (circular, or with some other shape) with a hollowed-out middle, and is used to stamp that contour, usually on the front face.

A lightweight "chasing hammer", to drive the punches.

An oxyacetylene torch, blowtorch, or a forge for annealing or hot-working.

Other tools are usually handy, such as tweezers or tongs to hold the hot plates.

The punches are usually made of steel, especially tool steel—a hard alloy that can keep its shape even after years of use—and are forged and tempered at the tip. They usually have a beveled rear end, to better handle the hammer blows. They can be purchased and used as such, modified by the user to suit the needs of a specific work, or made by the user from bar stock. To make or reform the punches, one needs a saw or other cutting device, as well as a grinder and abrasives to shape and polish the tip.

Use

Depending on the application, chasing can result in a relief, for example. This type of metalworking was and is frequently used in arts and crafts. It allows for the creation of high-quality yet durable ornaments or graphic representations. Metalsmiths, silversmiths, and goldsmiths also create unique bowls, vases (for example, using the winding and hammering techniques), lamps, jewelry, and even portraits (here, for the precision of detail, in copper or precious metals).

Metal working is still indispensable today, especially for architecturally integrated art or unique pieces in the design sector and small series, special pipeline construction or even in the field of restoration.

As car manufacturers increasingly strive to display every model ever produced in museums, entire vehicle bodies are increasingly being reconstructed by hammering. Specialists with decades of experience often perform this work. Even a curved fender requires many thousands of hammer blows and is correspondingly expensive. In earlier times, from around 1920 to around 1950, so-called mechanical hammers were used, among other things, to produce rounded car body parts. These were machines that very quickly applied light blows to the thin (steel) sheet metal, which had to be worked while cold, and could only be operated by experienced craftsmen.

An example of the use of solid material in relation to driving can be found in the history of the Tobiashammer in Thuringia. Here, a historically waterwheel-driven tail hammer was used until the collapse of the GDR in 1989 to produce kettles, pans, and especially kettledrums from a single piece, whose sound still sets a standard today.

A widely seen example of embossed metal today is the frame of the golden M in the McDonald's illuminated sign. It is embossed from a straight, L-shaped steel bar.

Perhaps even more popular is the Statue of Liberty in New York, whose shell was forged from 2.57 mm thick copper sheets. Or the 2 mm copper quadriga on the Brandenburg Gate in Berlin—created in 1793 by the coppersmith Emanuel Jury based on a design by Johann Gottfried Schadow.

Especially in Berlin, one can still admire many outstanding examples of figurative carving, for example, on the gables of the Gendarmenmarkt or at the Museum of Communication. Completely destroyed by the Second World War, the up to six-meter-high copper sculptures were faithfully reconstructed between the 1970s and 1990s by Berlin metalsmith and sculptor Achim Kühn.

Leather embossing

Leather embossing is an art practiced in Muslim Spain and later restored by the German Clauson Kaas.

This embossing is done by hand. The leather must be worked on both sides. A drawing is made on one side, and then the other side is embossed on the reverse. Leather embossing is used for the covers of luxury bookbindings, wallets, portrait frames, chair seats and backs, screens, etc., with decorations tailored to the craftsman's taste, whether gilded or colored, pyrographed with metal and enamel applications, and other combinations. 

Sourced from Wikipedia