from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun An impure oxide of cobalt, used to produce a blue color in enamel and in the making of smalt.
from The Century Dictionary.
- noun The residuum of cobalt-producing ores after the sulphur, arsenic, and other volatile matters have been more or less completely expelled by roasting.
from the GNU version of the Collaborative International Dictionary of English.
- noun A pigment obtained, usually by roasting cobalt glance with sand or quartz, as a dark earthy powder. It consists of crude cobalt oxide, or of an impure cobalt arseniate. It is used in porcelain painting, and in enameling pottery, to produce a blue color, and is often confounded with smalt, from which, however, it is distinct, as it contains no potash. The name is often loosely applied to mixtures of zaffer proper with silica, or oxides of iron, manganese, etc.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun A
pigmentobtained, usually by roasting cobaltglance with sandor quartz, as a dark earthy powder. It consists of crudecobalt oxide, or of an impure cobalt arseniate. It is used in porcelain painting, and in enameling pottery, to produce a bluecolor, and is often confounded with smalt, from which, however, it is distinct, as it contains no potash. The name is often loosely applied to mixtures of zaffer proper with silica, or oxidesof iron, manganese, etc.
from The American Heritage® Dictionary of the English Language, 4th Edition
For about two centuries before that determination, cobalt was prepared in Europe, converted to zaffer to make blue-colored glass and blue enamel, and from zaffer to smalt for painting.
The degree of fineness that could be achieved depended on a combination of characteristics, including the quality of the ore, the proportions of ore to flint and sand in the zaffer mixture, and the degree of fineness to which that mixture was ground before firing.
This caused the liquid to harden and, according to Peckitt, it also extracted harmful salts. reference The zaffer-niter compound was dried and powdered: a quantity of this mixture was added to a crucible (“pot”) of molten glass to create the desired blue color. reference
Ground zaffer was also the basis of the painters 'material smalt.
Once prepared, zaffer would be ground again, for use as a vitreous coloring material, in glazes and enamels.
The resulting glass was broken up and ground again — at this point it could be used as an underglaze, painted directly on the ceramic form. 4 reference To adapt this formula to painting on a glaze as here, the zaffer would be dissolved in aqua fortis, washed, and then combined with an equal portion of fondant.
The search for native cobalt, especially outside of Saxony or the Erzgebirge, was tied to the development of zaffer and smalt industries — refined versions of cobalt used by painters and in vitreous colormaking — and to recognition of the quality of the cobalt-based colors.
Instructions for creating zaffer blue, a color found on the plaque, called for firing the zaffer in a reverberating furnace for about twelve hours, followed by the addition of vinegar and by grinding and washing. reference This prepared zaffer was then mixed with the universal fondant and melted on a high heat.
Stamping and sifting was the next stage, before conversion into zaffer.
In general, the preparation technique called for the addition of coloring materials — metal oxides — to the molten glass mixture before molding or blowing or otherwise shaping: Peckitt's description of "A deep Blue Colour upon Glass" may be similar to the technique used to create the blue border here. 6 If so, his process was based on a mixture of zaffer and niter. reference The two were ground together and then added slowly into a hot crucible.