After studying and collecting European enameled orders of decoration for two decades and attending various bourses, I believe it is safe to say that there is an underappreciation of the original work that went into enamels. This relative need for more knowledge is shared equally among dealers and collectors, alike. Granted, both camps are quick to pick out whether or not there is missing enamel, cracked enamel or flaking. What I propose in this article is a distillation of the jewelry-maker’s original art and the difficulty with which it was executed, particularly in orders and medals that predate the 1940s.
Enameling, when done correctly, provides an outstanding example of human skill sets. The refined and sophisticated techniques did not arise out of thin air. Most often conducted by jewelers via authorization of either the crown or the chancellery/armorer of an order, fine enamel work was a craft driven and patronized by officers serving in the courtly realms of various kingdoms. The jewel-like brilliance of an order of decoration’s vitreous surface is durable and the colors range from the bold and vivid to the subtle and pastel.
Special ovens used thermal sensors and each box of enamel powder was printed with the temperature at which the craftsman would need to bake it to achieve the desired color. There were strict steps of whether you baked one color before the other, otherwise the maker would ruin the entire piece.
Continuing to address the subject of production from a macro standpoint, enameling involved fusing colored glass in powdered form to a surface. The glass is a flint glass containing between 25 percent and 40 percent lead oxide and the colors were obtained by adding small quantities of metallic salts. For instance, gold chloride gave a dark red, oxide of cobalt rendered a blue and iron oxide produced green. There will be more on these colorizing details later in the article. After being washed, the powdered enamel was mixed with water and applied to the surface and the piece was fired in a furnace. Many coats of enamel were required and, thus the piece had to be fired again each time.
That summary, though, begs further details. There were sophisticated and often frustrating challenges. If one part of the multi-colored piece was messed up during the intricate process, the jeweler one way or another had to start over. Let me explain these issues more fully. Technical problems inherent in the enameling process with the need for successive firings was a challenging fact, as colors change during firing at different temperatures. That made the production of a fine enameled piece something to be marveled at once it emerged successfully at the end of the process. We are talking of product that rivaled the work of the finest jewelers and if one will study the varieties of European orders of decoration, they will see a level of quality that almost presupposes the competitiveness of court jewelers to outdo each other.
As alluded earlier, enameling is an unpredictable art and a combination of intuition and science that demands perception as well as skills. We know that enamel is a vitreous glass glaze that is fused to a metal base, but continue to keep in mind that the chemical constituents are silica (sand), borates, alkalis (soda and potash), alkalines (lime, magnesia, lead) and oxides of metals for coloring. There are four basic types: opaque, opalescent, translucent and transparent. Production methods include: cloisonné, champlevé (raised field), basse-taille (shallow cut), guilloche (engine-turned), and plique a jour, also known as email de plique. There was also filigree enameling as well as en plain (on an open field).
Blue enamel is produced by cobalt. Carbonate of copper produces green, manganese produces purple, oxide of gold produces some pinks and reds. The color is affected by the constitution of the molten glass (flux) and by the type or quantity of the oxide. To make things even more difficult, most enamel colors could not be mixed to give a hybrid or intermediate shade. To be sure, most of these had to be prepared with their own specific oxide.
By changing the proportions of the ingredients, the opacity or transparency, hardness or softness of enamel was determined. It not only called for a knowledge of jewelry, but also of chemistry, for the maker was dealing with silica, arsenic oxide, potassium carbonate, borax, lead oxide, feldspar and the other elements and compounds.
That speaks much of the ingredients, moreso than the process. Here are the steps. The article had to be washed and placed into a diluted acid to etch the surface in order to give a necessary adhering bond platform. In bassetaille enamel, the metal groundplate was chased or engraved so that its modeled surfaces beneath the enamel formed a part of the design. Undulating surfaces were visible through the enamel that covers them and produces an impressive effect upon completion.
Raw enamel was pulverized with water until it reduced to a fine power. It was dried, then sifted through a fine sieve. Gum tragacanth, a white vegetable gum derived from sea plants, was applied in solution form to metal surfaces to bind the dry, sifted enamel before firing.
Add to this tediousness the fact that most often, multiple layers were needed and each must be dried thoroughly then fired before the next color was applied. Kiln furnace at temperatures would reach between 600 and 850 degrees Centigrade (or 1110 to 1562 Fahrenheit) – all the while timed to brief intervals. Intense heat was therefore required to reach a temperature that caused the compounds to fuse to the metal. When zeroing in on a part of the medal or order, rather than the whole piece, focused flames had to be directed onto the enamel to keep it flowing freely. Any soldered joints had to be protected, too, even when the work was fired again. At no time could a soldered joint be left unprotected. Steel tongs were used for placing enamel pieces in and out of the furnace. Steel trivets, fire-clay stilts and wire screens supported enamel pieces for firing.
Additionally be mindful that cooling in too quick order would have an undesired result and a brittleness that sooner or later could crack or scale off. As alluded to earlier, various colors would be fired at different temperatures, so that those colors able to withstand the greatest heat, such as blue and green, were fired first. Finally, the finish-up phase involved the filing down of the resulting enamel with carborundum until smooth, followed by a polishing with fine particulate pumice powder.
As a form of addendum, one should mention that there is another type of enamel apart from the silicate hard-type enamel that is baked and that is the fluid cold type, the latter being used most often to do repairs nowadays. The cold type used in restorations dries at room temperature for up to a day.
Illustrated Library of Antiques - Enamel, Washington, DC: The Smithsonian/Cooper-Hewitt Museum, 1983.
Maryon, Herbert. Metalwork & Enameling, Mineola, NY: Dover Publications, 2011.
Mason, Anita. An Illustrated Dictionary of Jeweller. New York: Harper & Row, 1974.
Winter, Edward. Enameling for Beginners, New York: Watson-Guptill Publications. 1962