Definición

• Goldplate, Goldplating.  Application of gold to any surface by electrodeposition. Because gold is an element that conducts electricity it can easily be electroplated. Developed at the same time as silverplating (which was invented in Germany in 1837 and patented in England in 1840) goldplating proved useful for coating small manufactured objects. Gold can be deposited in a very thin amount, even with a few microns the object takes on the color of gold.
  All but a few metallic surfaces can be goldplated. An object can be manufactured
  in any metal (most often an alloy) then goldplated to give it a gold color. This is done, obviously, to reduce cost, and yet to provide an object that has most of the qualities – except weight and fineness! – of solid gold.
  While any metal can be goldplated, the most practical is gilding metal, a copper-zinc bronze alloy which has excellent properties of being manufactured. There are several metals, notwithstanding, which cannot be goldplated directly, iron is one of these. However even these can be plated with an intermediate metal, like nickel, then this can be goldplated.
  Goldplated objects are also called gilt or gilded (see gilding). Goldplated silver is called vermeil, it has the color of gold but the sheen of silver. While similar in color, rolled gold is a clad metal where thin strips of gold are clad to a thicker base metal before blanks are cut and the piece is struck; it is not an electrochemical process. Gold leaf is an entirely different process from goldplating – it is a physical application of thin leaves of gold, not an electrochemical one.
  Color of gold in goldplating.  Yellow gold is free of impurities, but tiny amounts of other elements in natural gold will color (change the hue) slightly. White gold has silver or platinum impurities, pink or red gold has copper impurities, green gold has iron impurities, and the very rare black gold has bismuth impurities.
  Each of these, except black gold, can be obtained by goldplating, either in the tank at the time of goldplating, or afterwards. Yellow gold is obtained by "pure" goldplating without any other metal ions in the plating solution. While white gold could be plated with silver or platinum, the same results can be obtained with tin (as sodium stannate) or nickel in the plating solution. Copper is introduced into the solution for a pink or red gold. For a green gold effect, the object is plated with silver (potassium silver cyanide) and lead acetate.  See Gold Color Chart, gold.
  History of goldplating.  Prior to 1840 objects were covered with gold by laying on gold leaf, or by firegilding, a process employing mercury. The mercury fumes driven off were harmful to workers so the process was prohibited in advanced countries, replaced for the most part by goldplating.
  But firegilding continued even in America up to 1880s. Early electrolysis was run off primitive batteries; with the introduction of commercial electricity in the 1880s it became economical to do extensive gold and silverplating. This finally eliminated firegilding entirely.
  The earliest goldplating was done in quite small containers. The field has
  progressed, as one writer indicated, from the pint jar to the 50-gallon tank. However with the high cost of gold anodes, goldplating is done in small batches in small tanks. (Further details, identifying the people credited for developing electroplating, is given in the entry under electrolysis.)
  Technique of goldplating.  An anode of pure gold is required; the work – the object to be goldplated – becomes the cathode. Both are placed in an electrolytic solution, a cyanide bath containing some gold ions already in solution. Both are wired to complete an electrical circuit and the current supplied through a rectifier. Ions of gold are electrically charged and leach from the positive anode.
  The ions in the electrolyte solution are attracted to the cathode that is negatively
  charged and instantly deposited on the cathode (object). Time is a critical factor. The longer the object remains in the solution and the current is on – the greater the thickness of gold builds up on the object.  See electroplate, electroplating.
  Goldplating thickness.  Most goldplating is very thin with a brief time in the tank. A thin plating – called flash plate, or particularly for gold, a gold wash – is suitable only to give the object a gold color. This can be as thin as .000001 of an inch with a cost averaging 60 cents per square foot when gold was $150 an ounce (or 250th the cost of an ounce of gold). Such a plated piece cannot be finished in any manner other than lacquering. At this stage the gold can be rubbed off with repeated rubbing of human skin (collecting in the skin's pores or finger ridges).
  Longer time – and thicker plating – give a deeper coating of gold. This will be reflected in both color and texture of the piece, entirely resembling gold on all surface exposed in the electrolytic tank. heavy goldplate is a result of this thicker coating, it has been identified on some items made before 1900 as XX or even XXX (triple X or triple plate) gold. This thicker plating must be reflected in the higher cost, fifty to sixty dollars per square foot (one-third the cost of an ounce of gold) because of the greater amount of gold being deposited.
  Additional plating or hardness can be made by removing the item from the goldplating tank and placing it in the silver tank for only a short time. Adding one part silver say, to 50 parts gold, increases the hardness but still retains the gold color.  See hard goldplate.
  Advantages of goldplating.  Several reasons exist for goldplating medals: (1) gold medals are a class of award medals, (2) gilding is a popular form of finish, (3) gold is
  a desirable color for medals as a gift, jewelry or award item, (4) gold does not discolor skin when worn on the body, (5) gold covers up surface discolorations and shallow imperfections of manufacture, (6) it is a time-honored metallic color, and, perhaps most important, (7) gold finish does not tarnish.
  Medals can be easily goldplated because of their size and shape, thus goldplating is widely done in the medallic field. Thousands of medals can be goldplated from a single ounce of gold, the unit cost can be comparatively low even in times when the cost of gold is high. Medals, obviously, are goldplated rather than struck in solid gold to reduce cost.
  How to tell goldplate from solid gold.  Goldplate cannot be distinguished from solid gold by surface inspection. A test of nitric acid or touchstone will not differentiate the two. A tiny test cut is usually done on the edge of medals, searching for the color of gold or the base metal. This is not foolproof either as medal makers often choose a base metal of yellow brass or oroide because it will bleed yellow as does gold. (A nitric acid test at a test cut would reveal the base metal is not gold. See gold.)
  The most obvious difference will be the object's weight. Solid gold will be heavier. Thus a specific gravity test will not only reveal the solid gold status (versus goldplate) but also will reveal the karat content (from 24 karat down to 9 karat; 8 karat and less is too similar to the specific gravity of other metals). Pure 24 karat and 22 karat is more than twice as heavy as most plated compositions. Such a nondestructive specific gravity test is obviously recommended over the destructive form of a test cut.
  Marking goldplated objects.  Goldplated objects are not required to be marked in any way unless the base metal is another precious metal. Solid gold objects are, of course, required to be marked with their true fineness in most industrial countries (since 1904 in England, 1906 in America). This is a current obligation reflecting the heritage of hallmarking in which all gold and silver objects were marked with symbols to identify the true nature and fineness of the metal. (The U.S. Mint does not honor this law, however, and their 20th century gold medals are unmarked.)
  Now more progressive medal makers are revealing the nature of the base metal and better goldplated medals are edgelettered with the identity of the base metal and, often, the karat of the plated metal. This precludes the need of making a test cut, mentioned above, to see if an object is solid or plated.  See edge lettering and numbering.
  Reverse goldplating.  Electrolysis can remove gold from a surface as well as add
  metal – in effect stripping off the gold from the surface of a goldplated item. By reversing the electric current the cathodic object becomes the anode and gives up the gold on its surface. The anode becomes the cathode and the gold collects on its surface.  Previously depletion gilding obtained the same effect with firegilded objects. (Such objects need to be refinished quickly because this process creates an activated surface.)
  Goldplated medals.  The first goldplated medals were plated at silverware factories. Later (and particularly in 1890s) this was accomplished by jewelry manufacturers. Only in the 20th century were goldplated medals made by traditional medal makers; the wide popularity of "gold" award medals required medal manufacturers to provide goldplating as a necessary service to their clients.
  Silver medals were goldplated to create vermeil (particularly after 1960 for the bullion medal demand). Bronze medals were goldplated and silverplated to create
  the gold-silver-bronze medal rank like those used for the Olympics.
  Plating by national mints.  Generally, goldplating is never done by a national mint. Coins intended for circulation, or medals intended for public sale, may be struck of a gold clad composition but never plated inside the mint. The U.S. Mint has never had the equipment nor the authority to electroplate a numismatic item of their manufacture. In certain instances these have been done outside the mint:
  ?       A new design in 1883 of the U.S. five-cent piece (without the word cent) was goldplated outside the mint by unscrupulous persons who's intent was to passed them off as $5 gold pieces.
  ?       Exposition officials of the Panama-Pacific Expo in 1915 wanted a goldplated version of their medal designed by John Flanagan and struck at the Philadelphia Mint. The goldplating was accomplished by Tiffany & Co in one of its jewelry plants.
  ?       The issuance of a goldplated John Wayne Medal of 1979, was struck in bronze by the Philadelphia Mint, but was goldplated outside the mint by private companies.
  Imitation gold.  While goldplating is done to imitate solid gold (at a fraction of the cost), imitation goldplating can be accomplished with a gold tint lacquer (at even further savings in cost).
  References:                                                                                                     
  F1 {1876} Zowey.
  F2 {1949} Blum and Hogaboom.
  F3 {1954} Graham.
  F4 {1963} Brenner.
  F5 {1974} Lowenheim.
  F6 {1975} Lins and Oddy.
  F7 {1986} Rubenstein.
  F8 {1987} Romankiew.

  excerpted with permission from

  An Encyclopedia of Coin and Medal Technology

  For Artists, Makers, Collectors and Curators

  COMPILED AND WRITTEN BY D. WAYNE JOHNSON

  Roger W. Burdette, Editor

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