VOCABULARY TERM: PATINA, PART 2

Patina.

How To Further Beautify A Patina
Add an enamel.
Add a second patina color.
Do both sides in a different color.
Add a colorful object to the surface.
Add a stipple color effect (with spots of color).
Use masks and make in three or more patina colors.
Add a highlight with a contrasting color.
Add color with a tint lacquer.
Add a clear overcolor.
Add an undercolor.

Patina chemicals. The following chemicals are some of the more frequently used in patina finishes:

Ammonium carbonate (NH4)2 CO3.H2O. A mixture of ammonium bicarbonate and carbonate. Used for a bronze patina of bluish-green color. Also called "hartshorn."

Ammonium chloride (NH4Cl) A patina solution for coloring bronze a verde antique green. Also called "sal ammoniac."

Ammonium sulfide (NH4)2SO4 An excellent darkening agent for bronze and silver in highlighting during a finishing operation. The objects to be darkened are immersed in this chemical for less than ten seconds – the sulfide is the source of sulfur as the darkening agent. Also called "sulfate of ammonia" and "sulphuret of ammonia."

Barium sulfide (BaSO4) Used as a coloring agent for bronze medals for a light brown color, called "Old English."

Copper chloride (CuCl2) A patina coloring chemical producing yellowish-green color on bronze. Also called "cupric chloride."

Copper nitrate (CuNO3) Used for dark blue and green patina coloring on bronze. Also called "cupric nitrate"

Copper sulfate (CuSO4) Colors bronze green. It is the green corrosion on copper items in an atmosphere exposed to sulphur and moisture over long time. The composition of incrusted patina.

Ferric nitrate (Fe(NO3)2) For use only by very experienced finishers; colors a dark chocolate color. Care must be used, however, as some of the nitrate salts can spot the surface.

Liver sulfide (K2S) Used for a bronze patina on statues and medals; it produces a color from red brown to dark brown. Also called "liver of sulfur," "potassium sulfide," "sulfurated potash." Liquid sulfur. (S) Quickly turns bronze and silver a dull black.

Oil of lavender. A bronze patina of pale ashen green color, formed by adding yellow pigments to oil of lavender.

Potassium nitrate (KNO3) is a patina solution for turning bronze a dark red color. It is most used for tempering tool steel (heat treating dies) and for chemical analysis. It is also called "saltpeter."

Potassium permanganate (KMnO4)

History and cataloging. Bronze statues have been given protective finishes for centuries; often with patinas that are a distinctive color. But it is only since the 1880s that bronze medals have been given patinas for their distinctive color. The French were the first to develop patinas for art medals. This came about from the introduction of sandblasting a metal surface, then oxidizing and relieving this surface (known as french antique). To carry this one step further by using sculptural patinas to medals was a natural progression.

In cataloging work, medals with a color patina should be so identified. This has been observed in the past but only a rudimentary way, as the basic color of the metal finish. It is hoped that color standards can be established within the medallic field in the future and these utilized in cataloging art medals.

Patina terminology. Most patinas are named for the end color the formulas and applications produce. Even thought this technology is more than a century old it is still evolving in its terminology. An extensive word list including patina terms are given in the entry finish and finishing.

The dictionary plural of patina is patinae, but modern workers say patinas. Both are correct. Also the verb is patinate, and past tense is patinated. The noun form of an existing metal coloration is either patina or patination. To do over a patina is repatinate.

References:

T1 {1878} Spon.
T2 {1892} Hiorns.
T3 {1904} Austen.
T4 {1907} Hiscox.
T6 {1925} Field and Bonney.
T7 {1962} Fishlock.
T11 {1983} Hughes and Rowe.
T12 {1985} Brachert.
O37 {1977} Julian, pp xxxv-xxxvii.

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.

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