Dick Johnson submitted this important but lengthy entry from his Encyclopedia of Coin and Medal Terminology. Thanks! Here's the second and final part. -Editor
Relieving and highlighting. Dry ground pumice in very fine grain size is mixed with water until it has the consistency of thick soup. The operator douses a slurry
of this mixture on the surface of a darkened medal while he holds it in his hand. It is then buffed by hand on a motorized muslin buffing wheel by lifting the dripping medal
upwards under the rotating wheel. (The wheel is rotating counterclockwise, otherwise the operator would get a face full of slurry. A splash guard behind the buffing wheel collects
the spun off slurry instead.) It is certainly understandable why this equipment is called wet wheel and the process wet-coloring.
The operator rotates the medal by hand then makes a couple of passes under the buffing wheel. The buffing action heats up the medal. By adding more pumice slurry he lowers the
temperature so his fingers can control the medal. He repeats the slurry and buffing process as often as necessary for each side of the medal. Then he will buff the edge, rotating
it while the revolving buffing wheel is in motion. Skill comes in handling the slippery moist medal, and not dropping it, while making an even two-tone color on both sides, with
an edge to match.
The buffing wheel removes the darkened surface in areas where it can reach – flat surfaces and high areas of the detail. Since it does not touch the surface in the crevices and
the corner areas it does not remove the darkened surface there. Thus the completely relieved medal would be light (the color of the original bronze or silver) on the flat and high
surfaces, and the contrasting dark color in the crevices and corners. This total process creates the light-and-dark, two-toned effect to give it its highlighted appearance. The
optical effect is to make the object's relief in greatest contrast for the human eye to perceive. Highlighting accomplishes this.
Drying and lacquering. After their treatment under the wet wheel, the medals are washed under running water of all the pumice slurry. They are then laid on a flat
rack accommodating a dozen or so medals to be dried. The rack is then placed under ultraviolet lights (or in an oven) to completely remove all moisture.
Moisture is the enemy of the next step – lacquering. A wet spot, the tiniest bit of water, or a person sneezing on the medal's dry surface, will, in time, cause dark spots
to form on the medal's surface under the lacquer (it is even called water spot). Every effort is made to dry the medals thoroughly, both sides, then get them in the lacquer
spray booth at once. The rack is laid on a turntable in the spray booth. A spray gun – the best method
For applying lacquer – is passed over the medals once back and forth. The rack is rotated one quarter turn. The medals are sprayed again, once. Thus the medals have received
the minimum amount of lacquer but in two directions, once horizontal, once vertically.
This thin coating of lacquer is perfect. It is so thin (less than a few thousandths of an inch) it cannot be seen with the naked eye. With any additional spraying the lacquer
would build up in the corners and be unsightly. Dipping causes this more so, and brushing (the only other ways of applying lacquer) leaves brush marks. Spraying is ideal.
Applying the light lacquer coating while the medals are still warm from their heat lamp drying treatment will give a matte appearance to their surface. If a glossy finish is
desired additional passes of the spray gun with a heavier coating will increase the reflectiveness to give the surface a shinny appearance.
The lacquer is usually clear. However, the lacquer can be colored, by adding metal powders (bronze powders), dyes or tints. Thus the spraying can keep the color of previous
metal coloring (with transparent lacquer), or change it drastically, or only slightly.
With one side of the medals sprayed both directions, an empty rack is placed over the medals, and by holding the two racks tightly together, the operator can flip this over, to
lay the second rack on the turntable and spray the second side of the medals. The lacquer drys almost instantly, the finishing of the medals are now complete and need only to be
carried to the next workstation for any mounting, fabricating, edge lettering or numbering, or for inspection and packaging.
Imitating gold and silver. Not surprising, a lot of the activity in the finishing department is to make metal objects appear more attractive or desirable. Base
metal items are often desired to be colored gold or silver. Undoubtedly this is a carry over from the jewelry field where so many of these processes were developed. Objects are
struck or cast in base metals for the lower metal cost and given a surface, or coating, or finish, to appear as the more expensive noble metals.
While some metal compositions are chosen to imitate gold – brass, goldene, oroide – several methods imitate gold with layering (as rolled gold), clad, or electroplating with
the outer layer actually gold. nickel silver is a composition in imitation of fine silver. But silver can even be imitated with silver wash, silvered, silverclad, and silverplate.
The finishing department must be able to work with all of these, but most often utilizes gold and silver plating.
Electroplating. A well equipped finishing department for medal manufacturing will require both gold and silver electroplating tanks. These are used for finishing
medallic items with the required surface color by plating. Usually, because the finishing foreman has the knowledge of electrolysis, he is also in charge of making galvanos by
electrolysis even though this is a production of the item, not just the finishing (unless the galvano is required in a further production step, as a dieshell, in which case it is
not required to be finished).
Medallic items to be plated are placed on racks which are immersed in the electrolyte solution. Anodes of the pure medal – gold or silver – are also in the solution. The items
to be plated are the cathode. Electric current is turned on and, by the process of electrolysis, the metal is leached from the anodes and deposits on the cathode (the medallic
items). A further description of this process is given under the entry on electroplating.
Patina finishes. While oxidizing (sulphatization) with a darkening chemical and highlighting (by relieving) is but one method of finishing a medal, a medal can
also be finished with a patina. Patina finishes offer a range of surface protection – in a spectrum of possible colors! With a quantity of browns and greens for bronze items and
grays and blacks for silver. The choice of a patina is an artistic one, it should be made to harmonize with the design or amplify the theme. It is often made in consultation
between the sculptor or creator of the design and the finishing department foreman.
Each patina finish has its own methodology, and these techniques of application may range across a broad spectrum of activities. The variables concern: (1) the temperature of
the medal, (2) the temperature of the patina solution, (3) how a solution is applied, (4) how long a solution is applied, (5) the type of applicator (if any), (6) any wet wheel
application, (7) how a medal is supported while work is performed on it, (8) how the solution is allowed to set or dry, (9) pH of an acid solution, others.
There are, perhaps, forty or more commonly used patina formulas for medals. This despite the 1,126 different patinas listed in Hughes and Rowe, the standard work on patinas for
the field of metal coloring. The authors recommended only 344 of these formulas and techniques. The Society of Medalists issues, created by Medallic Art Company, all have
different patina finishes up to about issue #96. Although some are slight modifications the attempt of the Society was to issue a different patina for each issue. This medal
series exhibits, therefore, examples of what can be done in a modern finishing department. An even more dramatic series was the Religions of the World, issued by Presidential Art
Medals in which 15 different medals, each a different religion, each with a different patina.
The entry under patina lists the colors, chemicals, and names of the more popular patinas. The reader is directed there for these specific patinas.
Enameling adds color. The finishing department must also be able to do enameling as well as other finishing processes. Enamel adds color by applying tiny colored
glass beads in an enclosed area on the surface of a medallic item. The cloisonné process requires fences or sides of relief to contain these loose beads, but an astute designer
can work these raised surfaces into the overall design. Separate color beads are added for each different color.
With the medal laying flat and all areas to be colored with enamel filled with loose glass beads the piece is then fired. It is placed in an oven which melts the beads which
become hardened and fixed in position. Enamel is essentially colored glass applied to a metal object. It is the most ideal way to add different colors to a medallic item, the
colors are permanent and solid. However, since the enamel is glass it is susceptible to breaking, particularly near the edges.
Fabricating and mounting. To complete a medallic item the finishing department is required to do any final steps in its manufacture by fabricating – bringing
together any additional assembly, like placing a ribbon drape on a medal – or mounting the item, as on some other object. Further details on these can be found in the entries on
fabricated and mounting.
Thus we have observed that in contrast to coins, which require no finish (that's why it's called coin finish), medals require and can be adorned with a great variety of
finishes. It is the finishing department that accomplishes all these functions.
Word List #19
Terms of Finishes, Finishing and Patinas
abrasive blasting: jewelry finish
acid patina: lacquered
aerugo nobilis: Light brown
antique bronze: Light bronze
antique finish: luster
antique green: mahogany finiah
Antique silverplate: mat, matte surface
applied finish: matte-ground
appressed finish: Medium brown
artistic green: Metallic bronze
blacking: Old English
Blue (turquoise): organic coating
bright dip: oxidation
bright finish: Pale brown
bronzing: Pale red-brown
Brown-gray: pearl essence
Brown-green: Red bronze
brush finish: Red mahogany
Chocolate brown: relieved
coin finish: Roman gold
colorized: Rose gold
color sample: Russet brown
Copper antique: satin finish
Dark brown: scratch brush
Deep yellow goldplate: sgraffotp
French finish: Steel gray silverplate
French-gray finish: stipple
Glossy light bronze: tinted lacquer
goldplate: torch finish
gold tint: undercolor
Gray-bronze: vapor finish
Green patina: varnished
Green-blue: Verde antique green
highlighted: wet colored
immersion finish: White brown
incrusted patina: yellow-bronze finish
The terms in SMALL CAPS have entries in this encyclopedia; those terms not in small caps have meaning the same as every-day language.
Book lovers should be word lovers as well.
Looking for the meaning of a numismatic word, or the description of a term? Try the Newman Numismatic Portal's Numismatic Dictionary at: https://nnp.wustl.edu/library/dictionary
Or if you would like a printed copy of the complete Encyclopedia, it is available. There are 1,854 terms, on 678 pages, in The Encyclopedia of Coin and Medal
Technology. Even running two a week would require more than 19 years to publish them all. If you would like an advance draft of this vital reference work it may be obtained
from the author for your check of $50 sent postpaid. Dick Johnson, 139 Thompson Drive, Torrington, CT 06790.
Wayne Homren, Editor
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