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Book IX artificially coloring of metals such as gold, silver, copper

Book IX artificially coloring of metals such as gold, silver, copper Page of 251 Book IX artificially coloring of metals such as gold, silver, copper Text size:minus plus Restore normal size   Mail page  Print this page
190
DE NATURA FOSSILIUM
ammoniac has been dissolved. It is then placed in molten silver or one of the metals or alloys mentioned above. If left in the molten metal for a short time it becomes covered with it. Copper workers, in order to avoid the expense of making sal ammoniac, cover the inside of copper vases with pitch and pour the molten tin over them until they are covered. Similarly, iron workers add tallow to the molten tin and then, after polish­ing their object, coat it with the tin without rubbing it with vinegar and sal ammoniac or coating part of it with pitch. Verdigris does not form on brass that has been coated nor rust on iron. The advance of copper and iron rust is checked by the metals with which the objects are coated. This method of coating is not only seemly but very useful since it prevents flaws and gives a more pleasing taste to liquids that are placed in them. Enough concerning these things.
Artificial metallic substances that do not have the appearance and form of metals follow. These are made either within or outside furnaces. They form within the furnaces when ore is smelted or when one metal is sepa­rated from another or when copper is melted in a furnace and alloyed with other metals. When metallic ores are smelted in the first furnace many metallic substances are produced, namely, slag, stone, diphryges, cadmia, pompholyx, spodos, and flos aeris. When one metal is parted from another in the second furnace whose large shallow crucibles for separating the metals are called by our people foci6, litharge, plumbago, and spodos are the principal materials formed. When copper is alloyed or refined pompho­lyx and spodos are produced.
Metallic substances are produced outside of furnaces from metals either mixed with acid and finely powdered, producing verdigris, caeru-leum, or cerussa; or having been set on fire, producing ochra plumbaria, or minium; or driven to the top of a vessel, producing sublimate of mercury as the chemists call it, or sublimate of cadmia; or by a certain special process, producing cinnabaris. Finally some metallic substances may be hammered from metals such as scales of copper and iron.
Metallic substances may be produced from other metallic substances either in Nature, such as native minium, or artificially, such as artificial minium, or by both methods, such as psoricum.
I shall treat first slag which the Greeks call σκωρία. It is the excrement of metallic ore that has been refined in a furnace. It separates from the molten metal as the latter flows from the furnace into a crucible. The slag of silver, since it is usually drawn out into long threads when it is removed from the crucible with hooks is called 'έλκυσμα by the Greeks. The slag that is formed in smelters where copper is separated from silver acts in this same fashion. Slag forms from ores of gold, silver, copper, tin, lead, and iron but not from ores of quicksilver and bismuth since these ores are not smelted because of the ease with which the metals can be extracted
5 From the word for hearth.
Book IX artificially coloring of metals such as gold, silver, copper Page of 251 Book IX artificially coloring of metals such as gold, silver, copper
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