Quantcast
  Due to a new server, slow response may occur for which we apologize Portal logo
Login/Register
Bactrian Gold Treasure from Afghanistan, coming soon....
/gemstones/agricola_textbook_of_mineralogy/page_208 - 2
 

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
196
DE NATURA FOSSILIUM
Foam is produced now, as in former times, in many places. The best is made in Misena and Bohemia. Dioscorides gives preference to that from Greece which was produced at Mt. Laurium and called lauriotis. He places the Spanish second and the Puteolian that was made from sheets of lead, third.
Galen believed that foam of silver was moderately drying but obviously it neither warms nor cools. It is moderately cleansing and astringent. Among the ores it has merits of a moderate order and is often mixed with other substances that are either strongly astringent or biting. By itself it is only used for diseases of the thighs. That made from copper and lead, such as is produced in smelters where silver is parted from copper is moderately warming. Although this variety, being of an intermediate composition, tends to be warming plumbago is said to be cooling according to the Latins, although the two do not differ in other ways. When pro­duced from copper and lead it is of uniform composition.
The material the Latins call plumbago the Greeks call μολίβδαινα, each word having been correctly derived from the words for lead. It is produced from boiling lead when the upper part of the crucible takes up the lead itself in the manner already described. It is not of uniform color. The upper portion approaches the color of foam of silver, the lower por­tion a gray color and the intermediate portion a mixture of the two. The upper portion is the best, the intermediate, the poorest. Both the inter­mediate and upper portions have a certain luster and a reddish brown color when pulverized. When boiled in olive oil the color changes to liver-brown. The lower portion with a lead-gray color is impure.
Foam of silver is sometimes melted and colored with pigments and then used by potters to glaze the inside of their jars and by sculptors to glaze the outside of their works. At one time the warming furnaces of the Ger­mans were made in this same manner. They also use the powder for letter sand. Chemists make a powder from the gray portion of plumbago and call it plumbarius cinis. So much concerning foam of silver and lead.
Aerugo (verdigris), caeruleum (blue minerals), and cerussa (white lead) are produced by treating metals with acid. The various kinds of verdigris are made from copper. One variety is smooth, another full of holes. One variety is called santerna since it is used in soldering gold. The smooth variety is made in many ways. Sometimes strong vinegar is poured into a dolium or similar jar and a copper vessel placed over the top. It is better to use an arched vessel but if none is available a flat bottomed vessel will serve. It should be clean and without holes. After ten days the cover is removed and the verdigris scraped off. It is also made by suspending strips of copper in the dolium above the acid. These are left for ten days before the verdigris is scraped from them. It is sometimes produced by covering masses of copper or copper strips with wine that has gone sour. New wine will not serve. Sometimes copper filings or thin sheets are mixed with gold foil and then sprinkled with vinegar and stirred with a
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
Suggested Illustrations
Other Chapters you may find useful
Other Books on this topic
bullet Tag
This Page