Chasing (tʃeɪsɪŋ) is the opposite technique to repoussé, and the two are used in conjunction to create a finished piece.
While repoussé is used to work on the reverse of the metal to form a raised design on the front, chasing is used to refine the design on the front of the work by sinking the metal. The term chasing is derived from the noun "chase", which refers to a groove, furrow, channel or indentation. The adjectival form is "chased work".
The techniques of repoussé and chasing utilise the plasticity of metal, forming shapes by degrees. There is no loss of metal in the process, as it is stretched locally and the surface remains continuous. The process is relatively slow, but a maximum of form is achieved, with one continuous surface of sheet metal of essentially the same thickness. Direct contact of the tools used is usually visible in the result, a condition not always apparent in other techniques, where all evidence of the working method is eliminated.
The word repoussé is French and means "pushed up", ultimately from Latin pulsare "to push". Repoussage is actually the correct 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"); however, in English it has become common to use repoussé as a noun, and this usage is reflected in this article.
A famous contemporary sculpture created with this technique is the Statue of Liberty 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.
A second example of monumental copper repoussé sculpture is Portlandia by Raymond Kaskey, which was installed in 1985 in downtown Portland, Oregon. And a small example in QtVR you will find here by P. Netzer
The techniques of repoussé 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. Among the most famous classical pieces using this technique are the bronze Greek armour plates from the 3rd century BC.
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. By Hellenistic times, combined punches and dies were in use. In 1400 BC, the Egyptian Amarna period, resin and mud for repoussé backing was in use.
In 400 BC, the Greeks were using Beeswax for filler in repoussé.
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.
It can take some time to create jewellery using Repoussé and chasing, although with practice, complex and delicate pieces can be made which would be virtually impossible to complete using any other method. It takes a lot of time due to the repetition of a number of time-consuming stages: the preparation of a sheet by annealing; cleaning to remove the pitch between annealing and work; setting up; and careful work with punches.
One method of repoussé and chasing is to place a thin sheet of metal on a bowl of heated Pitch. The pitch is slightly soft, and hardens when cooled, or becomes liquefied when heated. The purpose of using pitch is to provide a solid base to work on, whilst allowing the metal to be pushed out and shaped without obstruction. The pitch is best worked on in a pitch bowl. This is a cast iron bowl which sits on a bag stuffed with sand or a similar substance. This allows for greater stability, rotation and angling. The pitch is heated using a hairdryer, or an industrial blowdryer. If the pitch is too hard, the metal will be thinned. If it is too soft, you have very little control over the form. Good pitch is hard enough to hold its shape, but soft enough to yield.
Steel tools are used to work the metal. A "liner" is a steel rod with a very thin, slightly rounded end, that is used to create the initial lines on the metal. The liner is hit on the end with a chasing hammer, pushing a thin line of metal into the pitch. The side facing up will consequently be the front of the piece. Once all the lines have been chased, the metal is then turned over on the pitch, and repoussé is then used to push the metal so that it extrudes on the front of the finished piece. The piece of metal is turned and worked many times, with numerous tools, before the final design is achieved.
Once a fairly large shape is inverted, it can be filled in with warm pitch to help maintain its shape. The pitch should be allowed to set in the forms before the piece is placed back on the pitch. Every time the metal is removed from the pitch bowl, it needs to be cleaned and re-annealed. Turpentine is used to remove the pitch, and a blow torch can also be used to burn it off.
There are hundreds of tools which can be used. They are generally made by the jeweller/crafts person. They are typically made from bars of tool steel, which is forged and tempered at the tip. A saw can be used to cut designs into the tip for making patterns, or the tool can be hammered onto a patterned surface, which will indent the tip. The end of the tool which is to be hammered should be bevelled to allow for expansion of the metal from repeated hammering. Some of the main styles of tool include: Liners, planishers, matting, and doming. Liners have thin tips, which are slightly rounded. If they are too thin they will cut the metal. They are used in the initial marking out of the design, and in the finishing stages to refine any thin outlines. Planishers have smooth, flat tips which are used for pushing out large, flat areas of metal. Matting tools have patterns cut into them, and provide detail to areas of the design. Matting tools can also be made by filing a thin line around a steel bar, hardening it, then snapping it. This will result in a fine grain pattern. Doming tools push out rounded areas of metal, and can either be round or oval, quite pointed or almost flat. An oxyacetylene torch is required for heating the steel sufficiently for forging. The more tools available, the easier it is to create a detailed, accurate piece.
The traditional working surface is chaser's pitch which is usually a composition combining three substances: pure pitch, a filler (or stiffener), and an emollient (softening medium). There are a number of different recipes for making chaser's pitch. One example is:
The pitch is heated until molten. Plaster of Paris is added a small amount at a time. Resin and tallow are then mixed in.
For a non-toxic recipe, try: 1 part beex wax to 1 part plaster of paris.