Gold

Gold is a chemical element with the symbol Au (from Latin: aurum "gold", originally "shining dawn") and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The native metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with tellurium. Gold metal is dense, soft, shiny and the most malleable and ductile pure metal known. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Gold is one of the coinage metals and has served as a symbol of wealth and a store of value throughout history. Gold standards have provided a basis for monetary policies. It also has been linked to a variety of symbolisms and ideologies.

History
Gold has been known and used by artisans since the Chalcolithic. Gold artifacts in the Balkans appear from the 4th millennium BC, such as those found in the Varna Necropolis, Bulgaria. Gold artifacts such as the golden hats and the Nebra disk appeared in Central Europe from the 2nd millennium BC Bronze Age.

Egyptian hieroglyphs from as early as 2600 BC describe gold, which king Tushratta of the Mitanni claimed was "more plentiful than dirt" in Egypt. Egypt and especially Nubia had the resources to make them major gold-producing areas for much of history. The earliest known map is known as the Turin Papyrus Map and shows the plan of a gold mine in Nubia together with indications of the local geology. The primitive working methods are described by both Strabo and Diodorus Siculus, and included fire-setting. Large mines were also present across the Red Sea in what is now Saudi Arabia.

The legend of the golden fleece may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. Gold is mentioned frequently in the Old Testament, starting with Genesis 2:11 (at Havilah) and is included with the gifts of the magi in the first chapters of Matthew New Testament. The Book of Revelation 21:21 describes the city of New Jerusalem as having streets "made of pure gold, clear as crystal". The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia around 610 BC. From the 6th or 5th century BC, the Chu (state) circulated the Ying Yuan, one kind of square gold coin.

In Roman metallurgy, new methods for extracting gold on a large scale were developed by introducing hydraulic mining methods, especially in Hispania from 25 BC onwards and in Dacia from 106 AD onwards. One of their largest mines was at Las Medulas in León (Spain), where seven long aqueducts enabled them to sluice most of a large alluvial deposit. The mines at Roşia Montană in Transylvania were also very large, and until very recently, still mined by opencast methods. They also exploited smaller deposits in Britain, such as placer and hard-rock deposits at Dolaucothi. The various methods they used are well described by Pliny the Elder in his encyclopedia Naturalis Historia written towards the end of the first century AD.

The Mali Empire in Africa was famed throughout the old world for its large amounts of gold. Mansa Musa, ruler of the empire (1312–1337) became famous throughout the old world for his great hajj to Mecca in 1324. When he passed through Cairo in July 1324, he was reportedly accompanied by a camel train that included thousands of people and nearly a hundred camels. He gave away so much gold that it depressed the price in Egypt for over a decade. A contemporary Arab historian remarked:

Gold was at a high price in Egypt until they came in that year. The mithqal did not go below 25 dirhams and was generally above, but from that time its value fell and it cheapened in price and has remained cheap till now. The mithqal does not exceed 22 dirhams or less. This has been the state of affairs for about twelve years until this day by reason of the large amount of gold which they brought into Egypt and spent there [...] —Chihab Al-Umari

The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion by Native American peoples, especially in Central America, Peru, Ecuador and Colombia. The Aztecs regarded gold as literally the product of the gods, calling it "god excrement" (teocuitlatl in Nahuatl). However, for the indigenous peoples of North America, gold was considered useless, and they saw much greater value in other minerals, which were directly related to their utility, such as obsidian, flint, and slate.

Although the price of some platinum group metals can be much higher, gold has long been considered the most desirable of precious metals, and its value has been used as the standard for many currencies (known as the gold standard) in history. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties. Gold as a sign of wealth and prestige was ridiculed by Thomas More in his treatise Utopia. On that imaginary island, gold is so abundant that it is used to make chains for slaves, tableware and lavatory-seats. When ambassadors from other countries arrive, dressed in ostentatious gold jewels and badges, the Utopians mistake them for menial servants, paying homage instead to the most modestly dressed of their party.

There is an age-old tradition of biting gold to test its authenticity. Although this is certainly not a professional way of examining gold, the bite test should score the gold because gold is a soft metal, as indicated by its score on the Mohs' scale of mineral hardness. The purer the gold the easier it should be to mark it. Painted lead can cheat this test because lead is softer than gold (and may invite a small risk of lead poisoning if sufficient lead is absorbed by the biting).

Gold in antiquity was relatively easy to obtain geologically; however, 75% of all gold ever produced has been extracted since 1910. It has been estimated that all gold ever refined would form a single cube 20 m (66 ft) on a side (equivalent to 8,000 m3).[39]

One main goal of the alchemists was to produce gold from other substances, such as lead — presumably by the interaction with a mythical substance called the philosopher's stone. Although they never succeeded in this attempt, the alchemists promoted an interest in what can be done with substances, and this laid a foundation for today's chemistry. Their symbol for gold was the circle with a point at its center (☉), which was also the astrological symbol and the ancient Chinese character for the Sun. For modern creation of artificial gold by neutron capture, see gold synthesis.

During the 19th century, gold rushes occurred whenever large gold deposits were discovered. The first documented discovery of gold in the United States was at the Reed Gold Mine near Georgeville, North Carolina in 1803. The first major gold strike in the United States occurred in a small north Georgia town called Dahlonega. Further gold rushes occurred in California, Colorado, the Black Hills, Otago in New Zealand, Australia, Witwatersrand in South Africa, and the Klondike in Canada.

Because of its historically high value, much of the gold mined throughout history is still in circulation in one form or another.

Cleaning

 * Mechanical

1.Ammoniated water
 * Chemical

0,1 lit water+add few drops of ammonia 25 %

Immerse objects in hot solution!

Rinse well!

Do not use on archaeology objects!

According to

Stambolov,T.;Bleck,R.D.;Eichelmann,N.

Korrosion und Konservierung von Kunst und Kulturgur aus Metall

Weimar I/1987.,II/1988.

2.Sodium thiosulphate solution

300 gm sodium thiosulphate

1 lit water

Immerse objects in solution!When it is clean rinse well! Can be used on other precious metals too! Do not use on archeology objects!

According to:

Schuberth, Hand und Hilfsbuch fuer Den Praktischen Metallarbeiter

Wien 1900.(???)

3.Acid cleaning solution

1-25 parts H2SO4

1-10 parts HCl

1-15 parts sodium hypochlorite

1 lit H20

Concentration depends on thickness of corrosion layers When cleaned rinse well,eventually neutralize in 5 % sodium bicarbonate solution.

Do not use on archaeology objects!

According to:

Riederer,J. Chemie und Kunst

Berlin 1977.

4.Gold cleaning solution

240 gm sodium bicarbonate

100 gm chloride of lime

40 gm sodium chloride

1 lit water

Immerse objects in hot solution,or wash it with soft brush!When they are cleaned rinse well!

Do not use on objects decorated with gems or pearls!

Do not use on archaeology objects!

According to:

George,G. Money making formulas

Sidney 1949.


 * Electrochemical

20-30 gms sodium hydroxide

30-40 gms sodium carbonate

10-20 gms trisodium phosphate

5-10 gms sodium metasilicate

1 lit water

60-70 C,5-10 A/dm2,5-6 minutes(4-5 as cathode,1-2 as anode),stainless steel anode

According to:

Halilov,I.H. Galvanotehnika dlya yuvelirov

Saratov 2003.


 * Ultrasonic

40 gms sodium carbonate

50 gms sodium nitrate

3 gms sodium metasilicate

1 lit water

2-5 minutes,then rinse it well and repeat if needs

According to:

Halilov,I.H. Galvanotehnika dlya yuvelirov

Saratov 2003.


 * Laser

There are well documented examples of  laser  cleaning  of  gilt objects:

1.M. Panzner, G. Wiedemann, M. Meier, W. Conrad and A. Kempe, et al.:Laser Cleaning of Gildings,Springer Proceedings in Physics, 1, Volume 116, Lasers in the Conservation of Artworks, Part I, Pages 21-28,2007.

2.S. Siano and R. Salimbeni:The Gate of Paradise: Physical Optimization of the Laser Cleaning Approach, Studies in Conservation Vol. 46, No. 4 (2001), pp. 269-281

Gilt objects - restoration
Gold plating solution/I

2,65 gm gold chloride

15 gm sodium carbonate(waterless)

15 gm potassium ferrocyanide

1 lit water stainless steel anodes,2 v

0,1-0,2A/dm2

Dissolve carbonate in boiling water,when it is dissolved add ferrocyanide,and when it is dissolved add gold chloride. Boil 30-180 minutes(add evaporated water!). When cold It must be filtered and then you can use solution.Object must be (grease and oxide free!) connected to negative terminal of current source,anode to positive.When gold layer is  formed stop   process, rinse it well and polish  with fine  brass wire brush immersed in  soapy water. Can be used on copper and its alloys,silver,tin,zinc,iron. More saturated variant can be used  for electroforming(40-50 gm gold chloride/200 gm potassium ferrocyanide/50 gm sodium carbonate/1 lit water,70 C ,4-6 A /dm2).

Warning: Never try to  mix  it with strong acids!Deadly gas will be  formed!

Use it only on damaged parts of object!

Gold plating/II

1 gm gold chloride

75 gm sodium phosphate

2,5 gm sodium sulphite

1 lit water,stainless steel anode,cca.6 v

Dissolve phosphate in hot water ,when it is dissolved add sulphite and when it is dissolved add gold chloride. Object(grese and oxide free!) must be connected to negative terminal of current source, anode to positive. When gold layer is  formed  stop  process ,rinse it well and  polish it with fine brass wire brush previously immersed in soapy water.Can be used on copper / copper alloys and silver.

Use it only on damaged parts of object!

Gilding powder

Dissolve 3 gm gold chloride in smallest  possible amount of water. With that solution moisten small linen rag,and when it is dry you must burn it.Obtained powder can be used for gilding-take some  of it with piece of cork previously dipped in salty water.Rub it on grease and oxide free object .When gold layer is  formed rinse well and immidiately lacquer.Can be used on copper and copper alloys and silver.

Use it only on damaged parts of object!

Leaf or powder gilding

Gold leaf or imitation gold leaf can be used.Gold powder can be used too.Bronze powder can be used instead it.Easy to apply and easy to remove.

Special paints

Mirrachrome(R) paint can be used.After application  cover it with golden dyed clearcoat.

Clearcoats

 * Paraloid B 72
 * Paraloid B 67
 * Paraloid B 44
 * Paraloid B 48 N

Waxes

 * Renaissance Wax
 * Cosmolloid 80 H
 * DIY Mixtures

Mechanical

 * Microsandblasting unit
 * Dry Ice Blasting(CO2)
 * Scalpel or burnisher
 * Needles(steel,wood,plastic,bone)
 * Stone setting hammer(vibrotool)