Repousse and Chasing Tutorial - Copper wall sculpture

      This coral inspired wall sculpture was formed from a single sheet of  copper. The only tools I used were a torch and a variety of hammers. This process of pushing flat sheet metal into 3 dimensional relief is called repousse and chasing.
     When copper is deformed it becomes rigid and inflexible. This is known as work hardening. Heating copper to temperatures near it's melting point relieves internal stresses and renders the material soft and pliable. This process is called annealing.
     The depth, or relief, in this piece was achieved by pushing the metal around from the front and back sides of the design, annealing as needed. Pushing the metal out from the back side is called repousse. Moving the metal down by impacting the front side is called chasing.

 

I began by cutting a large disk out of 16 gauge copper sheet. I annealed the metal and cleaned off the dark oxides left by the torch. I marked the areas which would be driven down from the front side (chased) with a sharpie.

I formed shallow craters by hammering inside the sketched out shapes, working the metal directly on my wooden table.
In this scenario the metal inside of the craters is work hardened.


I switched to a pneumatic hammer after I got the metal moving in the right direction. The air hammer pushes the metal quickly and with fairly uniform results.

While the craters are all work hardened, the areas in between them are still flexible. I pushed these areas out from the back side (repousse) to establish some high points. The shiny lines in this photo are the areas that were just hammered.

I turned the piece back over to work from the front. The metal in the center of the craters is being stretched by the hammer. I had to be careful not to push too far, or risk breaking through the thinning sheet.

              In this photo the basic high and low points have been established.

Next, I began shaping the ridges by hammering them in from the sides, towards the center of the raised peaks. Forming a crease or sharp point from an undefined raised area like this is called acumination.

The color in this photo is the result of annealing. Heating copper causes the metal to form oxides on it's surface. These oxides are messy and troublesome and need to be removed, unless they are intended to be part of the sculpture's finish. Copper is normally cleaned with something acidic or by mechanically scrubbing the surface. I clean copper with a weak sulfuric acid and water mixture, but have also used vinegar or lemon juice with decent results, although it is considerably slower.

The final bit of forming was adding a secondary inner ring within each crater. This was done by chasing these areas with the air hammer. The pneumatic tool has a variable speed adjustment which I was constantly playing with. The metal is never struck very aggressively, as that would thin it too much. Instead the metal is pushed around slowly in small amounts.

             The sculpture was chemically colored with liver of sulfur (or sulfur potash). This is called a patina. I will be discussing finishes in a later post. The completed piece is 25 inches in diameter and relatively lightweight.




                                       Coral inspired copper wall sculpture by Jeremy Maronpot
         

Here is a video slideshow of the process

Repousse and Chasing Techniques

Repousse and chasing are techniques for creating 3 dimensional relief in sheet metal. The process is a very old one which is often overlooked by metal artists today. It is a direct method of sculpting metal using simple hand tools and hammers. There is no loss of material when forming metal with these techniques - the metal is not cut by the tools but pushed into shape in small increments.  There are as many approaches to repousse and chasing as there are artists.  You can get some sheet metal to experiment with at Online Metals. Copper sheet is a good choice, in the thickness range of .032-.04".

Here are some of my frequently used chasing tools. These punches have a variety of specially shaped faces which push the sheet metal around by tapping on the tool with a hammer.  Most chasing tools are made from hardened and tempered tool steel. Tool steel has a higher carbon content than typical steel which makes it much harder and more durable. I have found that for my purposes, tools made of mild steel with lower carbon content work just fine. In fact, I have done some repousse work with wooden tools with good results. Matt Weber from Della Terra Studios makes some very high quality, high carbon chasing tools.

 The texture of the business end of the chasing tool will be transferred to the surface of the metal. Smooth faced tools like these are often used to move the metal into shape. Chasing tools with textured faces can produce different surface effects and are often used in the refinement stages of repousse work.

Repousse and chasing are commonly performed over pitch. Pitch is a resinous tar-like substance which is semi-fluid when hot and hard when cold. It provides a backing for forming the metal that supports it yet allows it to be deformed. The pitch holds the metal in place during hammering and prevents the material from being pushed around, other than what is directly under the chasing tool. The pitch is used at different temperatures depending on the amount or depth of forming required. The final stages of refinement, called planishing, are typical done on cold, hard pitch. Soft pitch has the resistance of wet clay if you were to press something into it - Not your finger! Pitch burns can be very severe and painful. A good source for pitch is Northwest Pitchworks.

This is the lid to a box that I formed in the pitch bowl. I worked the metal from the front and back sides of the design by flipping it over in the pitch multiple times. Repousse refers to pushing the metal out from the back side of the piece - chasing is pushing the metal down from the front. There is a lot of back and forth between repousse and chasing when creating a relief. As the metal is moved around it becomes stiff, or work hardened. The metal will crack if the stresses are not relieved. Think of bending a paper clip back and forth until it snaps. The metal can be returned to it's soft, malleable state by heating it to very high temperatures. This process is called annealing. Annealing temperatures are different for each metal and alloy but generally occur when the metal is red hot. Some metals must cool down slowly after annealing but copper and other non-ferrous metals can be quenched in water for a quick cool down.

I began this piece by drawing the design on the flat sheet metal and embossing the lines with a tool called an outliner or tracer. This tool has a business end similar in shape to a screwdriver but with rounded edges and corners. After the design was outlined I flipped the metal over and began pushing up the high points in between my traced lines. This is the back side of the design showing the types of tools used to create the depth. The piece was then flipped back over to define the shapes from the front.

In this photo you can see the faint impression left by the outliner tool in the lower right. This section has not yet been pushed out from the back side. Starting a project from the front with the outliner is a common strategy but not necessary. Some pieces are started by pushing out a large undefined area from the back and then pushing the low points back down, establishing the design by moving the metal from high to low.

Here is a sample I did for a client a few years back. The fingers and details were created with repousse and chasing, and then the metal was bent up into the cupped shape.

I do a lot of my repousse work with the aid of a hand held pneumatic hammer. This is an air chisel with adjustable speeds. The chisel tools have been modified by grinding, forging, and welding. The tools are just bigger versions of my chasing tools. The air hammer moves the metal quickly and with pretty uniform results. Saves lots of wear and tear on the hammering arm as well!

Here are some pieces that I formed with the pneumatic hammer.

Some of the most famous sculptures created using these techniques are the Statue of Liberty, Portlandia, and King Tut's burial mask. I have lots more to say on the subject of repousse and chasing. I will be posting step by step images of the techniques soon.

 

 See more examples of repousse sculpture