Analysis of Jewelry

Sterling silver

Created by the British is the alloy 925%. It is used everywhere and is a perfect compromise between hardness and oxidation. The silver 800% can no longer be used in food production because it releases too many copper oxides. Palladium was tested to make it work but it is very expensive and the outcome is ugly.

Precious metals

Precious metals are 4: Gold Silver Platinum Palladium All of these metals can be fused. There are then Rhodium, Ruthenium, Iridium and Osmium that are instead only in the form of salts and powders and are used especially for the alloys (Iridium and Ruthenium) or for surface finishing treatments (Rhodium)

importance of alloys

Precious metals are very soft but they can be strenthened considerably by the addition of other metals. The alloy is the combination of two or more metals. It is used in jewellery in order to allow precious metals (most of silver and gold) to become hard enough to be transformed into wire and plate and then passed through the other processes. The alloys are also used to modify the colour of the metal. It is very important to know how much alloy is inside the gold in order to know the right value of the piece.

Ductile

They can be drawn into wires finer than the human hair

Alloys of gold

23K = 958% 22K = 916% 18K = 750% 14K = 585% 9K = 375% International law says that under 9 it can't be considered precious metal.

Pure gold

24k or kt (carats) = 999.9% = pure gold Pure gold is rarely worked in order to make jewels only in some countries in middle and far east. It is very difficult to make shapes in pure gold because it's too soft and it's also too heavy. It's possible to make only elements very compact, not using wire or plate.

Quality mark

All jewels must be stamped with a number on the surface in order to make sure of the fineness: this mark indicates the proportion of the pure gold. This proportion can be measured in Karats (Kt or K) millesimal. The caratage is the percentage of fine precious metal contained in the jewel. The goldsmith uses the millesimal scale and blends gold with other metals in millesimal proportions. In Europe precious metals are measured using the metric system: Where pure gold, 24 karat, is given a value of 1000 points, 18 karat which is 3/4 pure, is given a measure of 750.

Where is all the gold in the world?

An approximate estimate by economists shows 30% in the reserves of central banks, 20% in private hands and 50% in gold jewellery. Every day at 10:30 am and 3:00 pm, the official price of gold is fixed. The price at the fixing is the one that allows the maximum number of buy and sell orders from all over the world to be matched.

Identification mark

Besides the fineness quality mark, the jewellery must also be stamped with the identification mark: all the information about the producer of the piece. Every country has a special rule about that, but the important thing is that you can have all the information about your jewellery piece in order to be sure about the quality of it.

Casting

Casting is an outstanding goldsmith's technique. It is the oldest and currently the most widely used technique in the manufacture of all kinds of contemporary jewellery. The simplest and most ancient variation of this technique was "open casting": molten gold was poured into a cavity shape made in hard stone or a cuttlefish bone; as the metal cooled it adopted the shape of the cavity. Casting provides an opportunity to make three- dimensinoal forms in metal from a form that we have carved or constructed from a wax or other organic material. A hollow plaster form is filled with molten metal to cast a three-dimensional form; a rubber mould can then be made to produce additional copies. Centrifugal casting is used to make one-off pieces of jewellery, or multiple pieces using different materials. Each stage of casting requires skill and expertise and involves vacuum casting machines, computer controlled temperatures, silicon waxes and high technology and melting furnaces

Characteristics of Precious Metals

Characteristics of the precious metals is that they are very rare and ductile and malleable.

Gold 999.9%

Gold is the metal most commonly associated with jewellery. In its purest form, gold is very soft, it's the most malleable of the precious metals. Gold mines are found in South Africa, in the USA, Australia, Brazil, Russia, Canada, China, Philippines.

Gold alloys

Gold jewellery is made by adding percentages of silver, copper, zinc, palladium and other elements. The higher the percentage of gold there will be inside, the higher will be the value of the jewellery. A high content of gold preserves the jewellery from oxidation (which happens with a lower content of gold) and is unlikely to cause skin allergies.

Rapid prototyping

In the last two decades, the jewelry sector has evolved in a surprising way thanks to the development of 3D printers, these are able to transform designs made using highly performing software such as Rhinoceros into three-dimensional products. The use of these printers is widely used both in the creation of models and for prototypes. After the design development, we move on to the realization of the piece. In the past this could only be done by hand, in metal or starting from a block of hard wax, now instead there are highly specialized computer programs that allow us to transform the handmade design into a three-dimensional computer design, capable of being then "read" by a 3D printer and translated into a resin prototype ready for subsequent production in precious metals. 3D printers work both by subtraction of resin from a starting block or by addition of powders which solidify little by little in thin layers. Several objects can be produced at one time and the manufacturing process lasts several hours. The great advantage of this technology is given by the possibility of producing extremely thin protoypes, even cables inside and with perfectly executed details. In addition, the drain channel is already included in the prototype, so that it can then be used easily in the creation of micro-cast jewellery. The major producers of precious metal powders are also focusing their research on direct 3D printing of these metals; currently the processes are still too expensive and complex and there is not enough demand in relation to what the system can do, but the work is constantly evolving and the process of 3D printing is already able to offer possibilities that go far beyond the shape: one of these is the mixing of different powders such as titanium and white gold and even precious metals and ceramic powders, giving rise to pieces with unique characteristics in terms of color, appearance and weights. Finally, 3D printing process, jewelry produced directly with resins can be created ; a market also open to eco-compatible projects thanks to the use of recyclable and compostable plant-based plastics.

Production techniques

Jewellery-making is an ancient craft, and many of the techniques and materials used thousands of years ago are still used today. Rarely is a piece of jewellery constructed using only one technique and material. A single piece may have a cast section, a carved detail, an enamelled area and a claw-set precious stone.

Technical precious metal informations

Silver - AG - 10.5kg - 960°- 3.25 Gold - AU - 19.3kg - 1.063°- 4.3 Platinum - PT - 21.4 - 1.768°- 4.3

Silver 999%

Silver is the whitest precious metal. From the ancient times it has been used in jewels, objects and to produce coins. In nature we find it in crystals, thin layers, filaments, grains and nuggets, in Canada, Peru, Norway or in silver sulphate minerals in Mexico and Latin America. After gold it's the most malleable and ductile metal: it can be transformed into a transparent plate. It's very good to conduct electricity and light (the most effective one) and widely used in electric, electronic and photo industry. It's very resistant to oxidation: the change of colour on the surface is not oxidation but is due to the sulfur present in the atmosphere. As all the other precious metals, it is very soft (with a nail you can scratch it) and to be transformed into a jewel it has to be combined with copper. Copper is the only metal we add to silver to make it an alloy.

Silver alloys

The silver alloys legal in Italy are 800% 835% 925%

Extraction of precious metals and transformation in the jewellery industry

They are extracted normally from the mines, then are refined (taking out all the impurities and other metals) and melted into ingots. The ingots are melted with the pre-alloy in computer-controlled furnaces and made into bars. These can be passed either through rolling mills to make plate or into wire-drawing machine to make wire. The wire can be used to make chains: it goes into a chain-making machine and it can be very fine, as thin as 0.10 millimeters or less. The gold plate which can be of different thicknesses can then be shaped by a stamping machine.

Precious Metals Usage

They are used not only in jewellery but also in electrical, electronic and aeronautic industries because it's exceptional the resistence to oxidation and corrosion. Gold and platinum are also used in surgery and acupuncture because they are excellent energy conductors.

Malleable

They can be transformed in such thin sheets of metal to become transparent (pale gold leaf)

Platinum 999%

Very precious metal discovered in 1735 inside gold sands of Columbia, is white-grey, relatively soft, ductile, malleable and strong. Platinum is 30 times rarer than gold, you find it in few mines in the world. Most of them placed in South Africa and Russia and a little also in Zimbabwe, Canada and South America. Every year 90 tons of Platinum are transformed into jewels, compared with the 2700 of gold.