Historically, a wide range of techniques has been used to clad or coat silver or base metals with gold. These processes are based on efforts to balance three factors: cost, physical properties and appearance. Rolled gold or gold-filled stock is a widely used commercial form of clad material.
Doublée is a German word of French origin that is applied to rolled gold or gold-filled material. In this article the term will be used to differentiate between handmade and commercially produced sheet. Doublée is distinctly different than commercial material and can be produced in a wide range of thicknesses and alloys which may not be commercially available. Doublée is far less perfect and its size is limited by the workshop facilities available. Because of this freedom, numerous design options are available.
For a number of years I have been interested in gilding and gold overlay techniques. Prior to 1978 I made extensive use of fire gilding (mercury amalgam gilding) in my work. In 1979 I studied under Klaus Ullrich at the Fachhochschule für Gestaltung in Pforzheim, West Germany, an experience that sparked my interest in doublée making. During the 1960s Ullrich had made extensive use of 18-, 22- and 24-karat golds in his work, but as gold prices rose he began using doublée to maintain a pure gold appearance at a more reasonable cost. During a visit to his workshop I watched as he fused a 0.3mm 24-karat gold sheet to a 1.0mm sterling silver sheet. The material was heated with a large propane/air torch. Air was supplied by a foot bellows. The material was rolled to size. The shape of the sheet was controlled by directional rolling. The final rolling pass was done with paper imprinting to decrease surface gloss.
In the industry the fusing procedure is similar to the way in which mokume-gane is made. An example I saw in Pforzheim was a sheet of gold 10.0cm x 30.0cm x 1.0mm thick. The gold was scrupulously cleaned and placed over an equally clean slab of sterling, 10.0cm x 30.0cm x 10.0cm thick. The gold alloy most often used is 14-karat with slightly more silver than copper. Two steel plates (10.0cm x 30.0cm x 2.0cm thick) were placed over and under the gold and silver. The stack was wrapped in brass foil to exclude oxygen. It was put in a gas kiln (a controllable atmosphere, probably reducing) for six or more hours until it reached the correct temperature. It was taken out and placed under a drop press for bonding. The bonded slab was unwrapped and rolled out or stamped into various forms.
In 1980 I returned to Canada and established my own workshop. I began to experiment with fused metals to obtain the color of 24-karat gold and the strength of sterling at a reasonable cost. The first problem I encountered was the selection of a suitable torch. My first experiments indicated that acetylene was too hot and propane/air was too oxidizing. Eventually I settled on a mouth-type blowpipe and propane gas. This provided excellent control, and by combining this torch with a charcoal soldering block, a reducing atmosphere could be maintained. The blowpipe I use costs about $15.00 and is available from several European tool companies (see Suppliers). I sawed off the tip from a Bernz-O-Matic-type, small propane torch kit and clamped a rubber hose to the brass tube that was left to supply the blowpipe with gas. The air is blown into a second tube. The most difficult part of using a blowpipe is that the flow of air must never stop. This means that, like a horn player, one must breathe in while a reservoir of air held in the cheek supplies the torch. This is replenished as one breathes in and so the flame is never interrupted. Facility with this is best accomplished by practicing with one of the old-fashioned smaller blowpipes used with an alcohol lamp. The amount of heat produced is directly related to the air supply so the process is very direct and controlled. It can be done slowly enough to ensure that the metals bond without simply alloying. Alternatively, one can use bellows or learn to work with a sharper, hotter flame. A natural gas/air torch would work quite well.
Materials also have a strong influence on the system. While various gold alloys may be used, 24-karat gold offers the best probability of success. Its melting point is so far above that of sterling that it does not alloy easily. When alloying takes place during fusing, it is usually on the surface of the gold sheet and can be scraped or sanded off to restore a gold surface. Due to the extreme softness of 24-karat gold, however, the doublée is readily liable to damage. Even a fingernail can scratch a rolled-paper finish. Therefore, a 24-karat doublée surface should be protected from abrasion by surrounding walls and by function. Unsuitable for rings or bracelets, it is best for pins, earrings and small sculpture. Burnishing the surface effectively prevents further damage. Of course, a hard gold alloy may be used for the doublée material in order to create a harder surface.
The gold may be fused to fine silver or sterling. Sterling works well, but oxidation may present a problem that does not occur with fine silver. Conversely, fine silver is too soft for any load-bearing part of a construction. Gold may also be fused to copper, but this is extremely difficult because the copper-gold alloy formed melts at a relatively low temperature and spreads very rapidly through the gold. It is possible to use this effect with copper to create areas of varying alloy content (rose gold to red gold) on the copper surface and then bring out their colors by suitable chemical treatment.
My first efforts used 0.3mm gold sheet fused to 1.0mm sterling sheet. Fusion was conducted using a soldering flux. With more experience, I began using 0.1 mm gold sheet and 1.5 to 2.0mm silver. These later experiments were done without flux, relying on the reducing atmosphere of the torch and charcoal block. At first the process was treated as a way to obtain a plain gold surface. It soon became apparent that it would be possible to engrave through the surface to expose the silver and develop graphic patterns. Patterns could be engraved in the surface before rolling. Line width could be manipulated by rolling. Line width, texture and relief can also be modified by re-fusing. One may thus use the metal as one uses drawing media and paper.
The following details the doublée process on a studio scale:
The doublée process is one of several types of fusion that can be applied to numerous combinations of materials. It provides a method to produce a wide range of surface colors and textures in a reasonably controlled manner. It should be applicable to a wide range of forms, scale and design.
Charles Lewton-Brain is an MFA candidate at SUNY, New Paltz, after having owned his own business and taught in Canada for several years.
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