Composition of Metals

Gold

Gold is one of the three noble metals of the Earth (in addition to silver and platinum). A noble metal is a metal that is resistant to corrosion in water and can be worn without worry of any harmful reaction. It is a soft metal in comparison to other metals and for this reason, is appropriate for gold jewelry crafting.

History: Gold is a metal that has not lost its value throughout history and, therefore, there are many banks and trading systems that maintain their capital in the form of gold bars.

Attributes: Physically, having a tendency to conserve its energy, gold is considered a mineral with calming and warming effects, recommended for people who chronically suffer from cold. Mentally, gold is perceived as a symbol of prestige, wealth and success and gives its wearer energy of purity.
 

"Carat" (k), the unit in which the purity of gold is measured, is based on a division of 24 basic parts. 24 carat gold, which is the purest degree of gold, is a very soft metal and for this
reason, is hard to work into a finished product. In order to harden gold to achieve the degree of strength required for gold crafting, it is a common practice to add other metals such as silver or copper. The smaller the quantity of gold there is in the metal, the lower the carat.

For example:
14k Gold contains 14 parts (out of 24) of pure gold, that is to say 14/24 = 58.5% and it is stamped 585.

21k Gold is 87.5% Gold, stamped 875

18k Gold is 75% Gold, stamped 750

9k Gold is 37.5% Gold, stamped 375


Colors of Gold – The original color of pure 24k gold is a bright yellow. Gold that is lower than 24k has been combined
with other metals that affect and modify its
color.
Yellow Gold: In order to maintain the original color of gold in gold that is lower than 24k, equal percentages of silver and copper are used.
Red Gold: Gold with a higher content of copper will have a more reddish appearance. The higher the content of copper in the gold,
the redder its color will be.
White Gold:  Gold with a higher content of the white-colored metals - platinum or palladium - will be whiter.


It is important to note that Rhodium plating tends to wear off with time and must therefore be renewed now and then.
Jewelry composed of silver combined with gold is jewelry which is predominantly silver on which a 9k or 14k gold plate has been soldered.

Silver 925 – Sterling Silver – International Standard

Silver 925 is the international standard used in the jewelry industry and in silver crafting. Since pure silver is a soft metal for use in silver crafting, a small quantity of copper is added to harden it and give it the required strength. Silver 925, known as Sterling Silver is composed of 925 units out of a thousand (92.5%) and 75 parts (7.5%) of copper and other metals.

Silver tends to oxidize and tarnish:

a.    In contact with air (as a result of its natural moisture).

b.    In contact with a person's skin, especially in summer when moisture is greater.

Silver jewelry should be removed before entering a pool (due to its chlorine content) or hot spa containing sulfur.

Silver in contact with water: One may shower with silver jewelry as water is not a cause of tarnishing on jewelry. On the contrary, water cleans and refreshes the silver (with exception of jewelry mounted with certain gemstones (turquoise, pearls and obsidian) and Roman glass, which loses its beauty and quality when in contact with water.


How to clean silver jewelry which has tarnished

1.    Use a silver polishing cloth that contains a special silver cleaning product. The cloth should be kept in a closed bag to prevent evaporation of the cleaning product.

2.    When a polishing cloth is not sufficient, jewelry should be handed over to a professional jewelry cleaner. Professional cleaning is carried out in 3 stages:

Cleaning – The jewelry is put into a metallic vessel with chemical cleaning products for removal of tarnish. Tiny metallic pins or balls suited to the type of jewelry create friction between the jewelry and the cleaning products and thus ensure a thorough cleaning of the jewelry in every nook and cranny.

Shining – During the cleaning process, it may happen that the natural shine of the silver is somewhat spoiled. The shining process refreshes this and gives the silver a renewed lustrous, rich look.

Polishing – In the final stage, a polishing process ensures a perfect finish.

Oxidation

Oxidation of silver – Oxidation, which darkens silver, may be applied as part of the design of the finished product. This is to be distinguished from tarnish, the result of oxidation, which has occurred naturally to silver, over time. Oxidation is carried out by immersing silver in an acid called oxide (hence the name of the process). The oxide penetrates into all the grooves and darkens the jewelry. When the intention is to darken only parts of the jewelry (for example, only the grooves), the other parts are cleaned. The jewelry is then shined and polished in order to obtain a perfect finish. Oxidation gives jewelry a special antique, ethnic look.

Gold Filled – Combination of Metals (Gold, Silver and Copper)

Gold-filled is produced by a chemical or electronic process which bonds a layer of 12-14k gold on a base layer, thereby creating a material called gold filled. The percentage of gold in the metal has to be a minimum of 5%.

Assay Stamp: Gold filled jewelry is stamped with the fineness of the gold in the jewelry and the letters GF. For example, 12kGF means that the jewelry is made of gold filled containing 12k gold.
Take note! It is not compulsory to stamp gold filled and therefore, the jewelry will not always be stamped.

Advantages: Gold filled jewelry has the look of beautiful gleaming gold and its cost is low in comparison to gold. Remember! Gold filled contains other metals. Therefore, in certain cases gold filled is liable to react like other metals,including tarnishing. Gold filled can be refreshed and cleaned in the same way as silver is polished.

 

Gold Plated Base metal (Silver, Brass, etc.) with a thin coating of 0.5 – 5 microns of gold. The carat of gold plating ranges from 14k – 24k. The gold plating process is a chemical one and any metal can be gold plated. The actual plating can wear off with time but can be renewed.

ISI - The Israel Standards Institute – works in accordance with international gold standards. Its role is to assay (test) the purity of the gold in jewelry as determined by the producer.


The Israel Standards Institute assay symbol is a harp, beneath which the gold fineness is engraved. The assay is usually stamped on the jewelry reverse or beside the clasp. Often, the assay is so small that it is necessary to use a magnifying glass in order to distinguish the details.

When is Assaying Compulsory?

1.    When gold jewelry exceeds 2 grams in weight (earrings, 4 grams)

2.    When the gold weight of the jewelry exceeds 20% of its total weight, for example the gold in silver jewelry combined with gold)

Silver Jewelry – Silver jewelry stamped 925 by the producer does not have to bear the assay stamp of the Israel Standards Institute. When the assay stamp is requested for silver, it will be the pomegranate assay symbol.

 

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