HaS-Repousse-art - 4/23/05
"Hammer and Stake Repousse'" by Master Tamlene ap Guidgen, O.L.
This article was submitted to me by the author for inclusion in this set of files, called Stefan's Florilegium.
These files are available on the Internet at: http://www.florilegium.org
Copyright to the contents of this file remains with the author.
While the author will likely give permission for this work to be reprinted in SCA type publications, please check with the author first or check for any permissions granted at the end of this file.
Mark S. Harris...AKA:..Stefan li Rous
stefan at florilegium.org
by Master Tamlene ap Guidgen, O.L.
Based rather heavily on the work of Nahum Hersom, Pheasant Art Metal, Boise Idaho.
October 23, 1996
Repousse˘ is a very old process of hammering sheet metal (usually cold) to a desired shape. Hammers are applied from the top, and the metal (or ÔworkŐ) is supported underneath in various ways. The work may be supported with pitch, a leather sand bag, lead, wood, or a forming tool such as a stake. Typically several means of support are used in the course of a project. The work discussed here is mostly accomplished by hammering from the top and supporting the bottom with a stake.
Stake repousse˘ does not strike the hammer against the stake. Instead, the hammer strikes next to the stake. This is referred to as Ňhammering on airÓ. This is a very important distinction. If you hammer directly over the stake, you will thin the work a lot, and mark it heavily. Hammering on air softens the blow and the resulting mark, making it much easier to create the shape you desire. Some stakes are hollow forms, and the metal is hammered down into them. The hammering is still done Ôon airŐ, and is stopped when the metal reaches the bottom of the form.
There are two major types of metal movement in repousse˘, sinking and raising. It is very important to understand the difference. Sinking is the technique usually used in SCA armoring. Sinking is done by pounding the work into a depression or die. This thins the metal to fit the die. Raising is almost exactly the opposite. Raising is done by hammering on air. Raising thickens the metal in the area worked. Sinking has limits—once the metal is too thin, it splits. Raising has no limit except your patience (provided you anneal when needed). An object made by sinking has larger surface area when done; if raised, the surface area of the material becomes smaller. Both raising and sinking are useful techniques.
Quite stunning results are achievable by stake repousse˘. The amazing thing is that it is a fairly easy process. Very dramatic results are achieved by overlaying simple patterns, one at a time. Achieving these patterns requires a good selection of specially shaped stakes and hammers. Making these tools takes some time, but is not difficult or very expensive. Only a few stakes and a couple of hammers will take you a long ways. More specialized tools can be made as needed.
The following information is guidance to repousse˘, not a detailed set of instructions. The best way to learn this craft is to do it.
The first thing you must do with a piece of metal is to mark the outline of the work on it. It is not obvious at first what this outline must be, as parts of the work will be stretched and parts thickened. It is advisable to make a paper master pattern, and then try it in thin (easily worked) sheet metal. If the final form doesnŐt work—too much metal here, too little there—then modify the paper pattern with tape and scissors and try again (in thin stuff that is quickly and easily worked). Once you have a paper pattern that works, transfer it onto card stock and put it in a safe place.
The outline of a pattern can be easily transferred to the metal by a fine line, permanent marker (such as a Sharpie). Also marked on the metal are lines to guide the hammer in shaping the work, such as vein lines in a leaf.
Once you have drawn the outline on your metal blank, it is time to cut the waste away. Begin by punching out the corner of all acute angles. A sharp corner focuses stress, and during hammering, the piece will break at the corner if left sharp. Use a round punch from 1/32Ó to 1/8Ó or larger, depending on your pattern. Once all of the hammer work is done, you can file the corner sharp if this is important to the pattern.
Cut out the pattern using aircraft snips or a saw, depending on the thickness of the metal. Once all of the waste is removed, flatten the metal. Errors can be corrected by cold stretching. File all marks left by the cutting, as these will not only tear up your hands, but they will also focus stress and cause the piece to break during hammering. Filing is easiest done in a special filing vise that holds the work at an angle. These are fairly easy to make (and date back to at least Roman times).
Hammering in repousse˘ is a carefully controlled process. You must pay strict attention to putting the hammer blows in the right places, and be careful not to leave unintended marks by using the wrong tool.
You hold the work against a stake with one hand, and with the other swing the hammer. Hammering is a slow and deliberate process. You will almost certainly hammer too fast at first. You want precise control over where the hammer strikes, not rapid movement of metal.
Hammering is done either with the wrist or from the elbow, but no harder. Heavier material does not demand harder blows—instead you use a heavier hammer with the same blows. Control is all important. Hold the elbow of your hammer arm against the side of your body. Hold the hammer loose in your hand. If your hand cramps, you are either holding too tight or the handle is too small. Choking up on the hammer can give you better control.
Always hammer so that the concave side of the metal is worked against a convex surface. The convex surface should have a radius no larger than the work or the edges will mark. The work may be hammered concave up or concave down as needed. If the work is concave up, then the hammer must be convex (most hammers are). The convex side of the metal may be hammered with a flat face, such as in planishing, or a radiused face if you want to move metal rapidly. If the metal wrinkles, hammer the wrinkles out, or they will lead to cracking.
If you will be hammering for a long time, soak your wrists and hands in hot water first. Wrap your wrists. Handle large ball bearings and soak hands in hot water during the day to relax. Grandpa Hersom recommends taking alfalfa and yucca.
Despite the most careful hammering, your work will develop unintended marks from the hammers. These can be smoothed by hammering carefully over a sand bag, wood or a lead block. Note that wheel weights are harder than pure lead (pure lead is more useful). Sometimes the hammering is done with a soft hammer, such as wood, rawhide, or plastic. Final finishing can be done over a ball (work concave down) with a flat faced hammer (called planishing). Finishing is done by hammering directly on the stake or support.
Hammer 16 gauge and thinner cold. Start with the primary shape, and then add detail. Metal 14 gauge and thicker should be done hot, in the opposite order.
Both steel and copper are good repousse˘ metals. Copper is easier to work than steel. Cold rolled steel is convenient, as it has the black oxide scale removed (which is very abrasive and dirty). Small pieces of sheet steel can be had from food cans.
As you hammer on the metal, it work hardens. Once it gets hard enough, it will break. Annealing will soften the metal and allow you to work the metal further without breaking it. You can feel and hear the metal work harden with a little experience. Thicker metal will need annealing more often.
Annealing is different for ferrous (steel) and non-ferrous (copper) metals. Non-ferrous metals are annealed by heating them to a just visible glow and then rapidly cooling them. Ferrous metals are annealed by heating to red heat and cooling slowly. Air cooling should be sufficiently slow for ferrous metal and sufficiently fast for non-ferrous. Be careful not to take ferrous metal hotter than red heat; red heat causes a soft scale, while orange heat causes a hard scale that is difficult to remove.
Stakes come in simple and complex shapes. Just a few simple shapes will suffice to get a lot of work done. A good place to start is with three double ended stakes, whose ends are shaped into a blunt chisel point. The blunt chisel shape is called a fuller. Each of the stakes should have different radii on their ends; one fairly sharp, one medium, and one blunt. Tool (or spring) steel 1/2Ó to 5/8Ó square is suitable for the bodies of the stakes. The two ends of each stake are different; give them both the same radius, but make them different widths. One end should be narrow and crowned, the other wide and flat. The narrow end allows you to track through a tight curve, the wide end helps in going straight. The stake ends should be finished to a good polish.
Stakes are usually held in a vise. Be careful not to rest the bottom end of the stake on a metal part of the vise (such as the screw), as this will mark the bottom end. A thick leather pad helps avoid this problem.
Other families of stakes include ball, flat, cup and vee. All of these stakes come in several radii and sizes. The edges of a wood or lead block can be used as an improvised stake.
Stakes may also be made of wood. Wooden stakes are made much more quickly, and last surprisingly well with thin metal. Use wood that is not prone to splitting; fruit wood is excellent. Also good are black birch and maple. Ring porous woods like oak are not useful. Copper, brass and silver work better with wood than with steel.
Vise handles have an annoying habit of pinching your skin and giving you blood blisters. Prevent this by putting a rubber band on each side of handle, a ways in from the end. This can also be a convenient way of positioning the handle where you want it.
Some shapes of hammers can be bought, but they are pretty expensive. Purchased hammers are received rough; they require additional shaping and polishing before they are useable. Hammers can be made from high carbon steel fairly easily (with the help of a blacksmith).
It is very important to remove all vestiges of sharp edges or corners from hammers in the vicinity of the striking head. Any edge left will mark the work badly.
Hammer heads come in full round, square, rectangle/oval and tracing (thin). All shapes come in many radii; tiny to flat. Take the paint/varnish off of commercial handles for a better grip. Most commercial handles are too fat both where you hold the handle and in the narrow part (neck). A head that is a little heavy is better than a little light.
I donŐt have any specific period documentation. I suspect that armorerŐs references would go a long way.
References giving guidance on how to do repousse˘ are hard to find. Nahum is working on a book, but it is currently in extremely rough form.
Some books which may be useful in learning repousse˘:
ExposeŐ of ReprousseŐ for the Beginning Blacksmith by Robert Heath
Chasing by Marcia Lewis
Silversmithing, by Rupert Finegold and William Seitz, Chilton Book Co., Radnor, PA, 1983.
Nahum Hersom offers week long classes at his shop in Idaho.
Copyright 1996 by Steve Smith, <sos at alum.mit.edu>. Permission is granted for republication in SCA-related publications, provided the author is credited and receives a copy.
If this article is reprinted in a publication, I would appreciate a notice in the publication that you found this article in the Florilegium. I would also appreciate an email to myself, so that I can track which articles are being reprinted. Thanks. -Stefan.