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What is Electroforming?

Electroforming (sometimes called electrotyping) is based on the process of electroplating. However, in electroforming, an object is not simply coated with metal, but actually created from layers of metal that “form” within, and sometimes around, a mold. See the illustration below, which diagrams the steps of the electroforming process.

As with electroplating, a metal salt of the metal to be deposited is dissolved in water to produce a plating solution that holds metal ions. However, in electroforming, the next step is to produce a mold of the object to be created (step 1 in illustration). These molds are made from a variety of materials, such as wax, plastic, or rubber. Once a mold is completed, a wire is attached that will connect it to the negative pole of a battery. Then, the inside of the mold is coated with graphite or metal flakes, which makes its interior surface able to conduct electricity (step 2). Once conductive, the mold is immersed in the plating solution opposite a solid piece of the metal to be deposited, which is also equipped with a wire that will connect it to the positive pole of the same battery (step 3). Next, the two wires are attached to the battery to create an electric circuit that includes the cathode (the negatively charged mold) and the anode (the positively charged solid piece of metal). Just as in electroplating, the completed circuit provides the current (flow of electrons) needed to reduce the metal ions. It is at this point, when the metal ions are reduced, that metal begins to form within the mold (step 4).

Copper is the plating metal of choice for almost all electroformed pieces, and often, after objects are removed from their molds (step 5), lead-based solder is used to strengthen the back and edges or to join separate parts. In addition, a gold or silver layer (usually created through electroplating) is frequently added to the front for decorative purposes. Since electroforming can be used to make reproductions, sometimes electroformed objects are passed off as original cast objects when, in fact, they are not!

Electroforming process: 1) a mold is made; 2) a wire is attached to the mold and its inside surface is made conductive; 3) the mold is placed into a plating solution next to a solid piece of the metal to be deposited, which also holds an attached wire; 4) the two wires are connected to a battery and metal begins to form within the mold; 5) the metal coats the mold, after which the completed object is removed.

How Can You Identify Electroformed Objects?


Compare the images of the tray and vase shown below. One of these works of art was produced through electroforming and one was not. It is not always easy to determine if an object is electroformed just by looking.

Tray
Tray, 1909
Designed by Hector Guimard, French
Gilded copper
1 3/8 x 18 1/2 inches (3.5 x 47 cm)
Gift of Mme Hector Guimard, 1949
1949-43-1
[ More Details ]
X-ray image of tray
Vase
Vase, 1908
Designed by Hector Guimard, French
Gilded brass
10 9/16 x 6 7/16 inches (26.9 x 16.3 cm)
Gift of Mme Hector Guimard, 1948
1948-64-2
[ More Details ]
X-ray image of vase
In some cases, if you closely inspect an electroformed object, you might see small gaps in the surface. These defects formed during the plating process from debris or bubbles on the mold. A more definitive method of distinguishing solid from electroformed objects makes use of x-ray imaging. With x-rays it is possible to determine if lead-based solder has been used because the x-ray density of lead (its ability to stop or absorb x-rays) is different from that of the metal that was plated. So when the x-rays of the vase and tray are examined it becomes apparent that the tray is the electroformed work of art, as some areas appear patchy and whiter than others. The lighter parts show where the solder was applied: at the edges to join the front of the tray to the back and to the thin areas of metal that form the raised, curving decorations. Because electroforming produces a shell of metal within a mold, thin areas often occur and require solder to reinforce them. The x-ray image of the vase, on the other hand, shows no patchy areas. The darkening of the lower section of the vase suggests that the metal at the bottom is thinner than at the top, allowing the x-rays to fully penetrate that area.
 

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