Repoussé & Chasing explained

Repoussé is a metalworking technique in which a malleable metal is ornamented or shaped by hammering from the reverse side. There are few techniques that offer such diversity of expression while still being relatively economical.

Chasing is the opposite technique to repoussé, and the two are used in conjunction to create a finished piece. Whilst 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 quality 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 are usually visible in the result, a condition not always apparent in other techniques, where all evidence of the working method is eliminated.

Methods

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 liquified 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 simillar 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 it's 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.

Tools

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 expanison of the metal from repeted 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, acurate piece.

This article uses material from the Wikipedia article "Repoussé and chasing". It is licensed under the GNU Free Documentation License.