A surface treatment technique called "electroforming" is an applied technology of electroplating. According to the JIS terminology, "electroforming" is defined as a production, repair, or duplication method for metal products by electroplating. In English, "electroforming" is the most common terminology, but "electrotyping" and "electrocasting" are also used to refer to the same process.
A general electroforming process starts with depositing a metal layer of a certain thickness on a model (known as master mold or mandrel) by electrolysis of metallic salt solution (such as plating solution). Then, separate this electrodeposited layer from the master mold to form an object in reverse (negative) of the master mold. This electroformed object can be used as-is, but you can also form a positive object, which is a perfect replica of the master mold as well. In order to do this, first perform the resist separation treatment (pretreatment that prepares electrodeposited metal to be easily removed from the mold). Then, separate the mold after electrodepositing a metal layer of a certain thickness.
By repeating the same process using the inverted object, you can produce a number of objects replicating the master mold in the same dimensions.
In addition to separating a copied object from the mandrel, electroforming can be also applied by electrodepositing a metal layer directly over the substrate metal. This method is useful when you repair worn-out molds or shafts by overlaying their surfaces.

Electroforming can be classified into mold-release and plating-up methods.

1) Electroforming by mold release

In this method, products are manufactured by electronically depositing a metal layer over the master mold and separating it from the mold. Products manufactured in this way can be an extremely thin object like a mesh or a product as thick as several millimeters, such as an injection mold for plastics.

2) Electroforming by plating-up

This method is performed for repairing mechanical components or overlaying the worn-out surfaces by directly electrodepositing a thick layer on the substrate metal. This method is not designed for mass production. In most cases, all it takes is a single application of electroforming. The technology is applied for other techniques including electrosizing, electrocladding, and electroassembly.

Electroforming by plating-up is a method that deposits a thick layer by applying general electroplating for a long period. Electroforming by mold release has the following subcategories:

a) Transfer method (separating an electrodeposited layer by the resist separation treatment applied on the master mold);
b) Impression technique (replicating an original item using plastics, varnish, or cements when only one of those is available; such items include fine arts and crafts or items made of wood, leather, or textile);
c) Material removal by melting (creating an original mold with low-melting-point alloy or wax to make an electroformed shell after removing the mold material)

Electroforming is utilized for a wide range of applications, including fine arts and crafts, production of electronic and precision components, etc. Without electroforming, you cannot manufacture some of the complex-shaped items that are not compatible with machining. When the electroforming technology first became available, copper was the main material because of the stable characteristics of its solution suitable for electrodeposition. Today, nickel or its alloy material has been adopted for their superior mechanical strength. In addition, nickel aminosulfonate solution has speeded up the electroforming process.