Metal Carats and Purities
Jewellery items are usually stamped with the metal/s that they are made from. It is illegal in most countries to sell unstamped jewellery items and to also stamp a jewellery piece with a stamp that doesn't match the carat.
Most common carats used in jewellery pieces in Australia:
- PT, 950, 900: Platinum. The most common alloys of platinum used in jewellery production is mainly either 950 or 900 platinum. The 950 means that it is 95% pure platinum and 5% of other metals. The 5% of other metal can determine what the platinum is most useful for i.e casting or fabrication. Some jewellers will also have a preference as to which platinum they use. The other carat of platinum used (900) has 90% pure platinum and 10% other metals. It is the platinum alloy that is most often used by jewellers as it produces an alloy that is not only easy to work with, but also holds the characteristics that make platinum an ideal choice for most jewellery.
- 999: 24ct Gold is the purest form of gold that can be used in jewellery, but is often too soft for working in and wearing.
- 916: 22ct Gold is a gold alloy that is 91.6% pure gold and 8.4% other metals. It is often used in jewellery production and is favoured in some countries more than others. It's purity gives it a rich yellow colour, but also makes it somewhat softer, which can effect long term wear.
- 750: 18ct Gold comes in three main metal colours: Yellow, White and Rose. Each of these are alloyed with different metals to give them their colours as well as to make them useful and easy to work with for making jewellery. 18ct Yellow gold has 75% pure gold and 25% other metals including copper and fine silver. 18ct White Gold is also 75% pure gold, but the remaining 25% of other metals are white, including silver, palladium and platinum. 18ct Rose Gold is 75% pure gold and then mainly copper is used in the remaining 25%, giving it it's colour.
- 585: 14ct Gold mainly comes in white, yellow and rose gold. It has 58.5% per gold content with the remaining consisting of metals like copper, fine silver and palladium with white gold having more white metal alloys and rose gold, copper.
- 375: 9ct Gold mainly comes in white, yellow and rose gold. 9ct Gold has 37.5% pure gold content with the remaining 62.5% consisting of metals like copper, silver and palladium, with white gold having more white metal alloys and rose gold, copper. 9ct Gold can be a harder metal, and this is because of it's lesser pure gold content and the addition of a higher percentage of alloys than the other more commonly used golds with a higher carat and gold purity.
Fabrication Methods
Many methods can be used to fabricate your jewellery piece. Some of these methods and techniques have been used for centuries and some are a more modern invention.
These are a few of the more common methods used: jewellery pieces can often incorporate one or many different elements of fabrication
- Handmade or hand fabricated: This piece/pieces have been made entirely or mostly by hand without the use of materials that have been previously fabricated not by hand (mass casting, CAD).
- Casting: Some pieces may be cast or have components that may have been cast. Casting is process that has existed for centuries, where an object or wax model has a mould made of it and the mould is then filled with metal when it is in a liquid state, or other elements such as resin. The piece/s is then cleaned and used in/as the intended jewellery piece. Some jewellery pieces may make the use of some smaller cast elements such as settings or specific cast objects to add to the whole jewellery item. Many found or natural items can be cast in metal, such as seed pods and insects to plastic objects such as party favours and lego.
- CAD (Computer Aided Drawing): CAD is a process that is commonly used in modern jewellery industry. It is a process where the jewellery item can be manipulated and drawn on a computer using a specific program and then printed in either wax or resin and then cast. CAD can often be used to offer more flexibility with very difficult, or seemingly impossible pieces that may not be made easily by hand or carved in wax. A CAD program can also be a useful tool to show a complete picture of a jewellery item before it has even been started.
Metal Finishes and Textures
- Polished: The metal is polished with compounds to produce a high lustre.
- Brushed/Matte: Metal has been brushed/rubbed with an abrasive to achieve a soft/mild textural effect. The texture may be in a single direction to achieve a matte effect or in many directions for a more dramatic effect.
- Sandblasted: The metal surface is textured using small polished glass beads/granules at high speed.
- Hammer texture (chasing): The metal surface is textured using a hammer. Different sized and shaped hammers achieve different effects. Small tools can also be used to give a chased effect such as punches and other specialised tools, which are forced into the metal surface.
- Roller Texture: Roller textures are achieved by using a another material which is then rolled atop the metal through metal rollers. The materials are wide and varied and can range from string and wire to netting and lace.
- Diamond texture: Diamond texture is achieved through the use of a tool that has been highly polished to a point (or many points) or has been set with diamonds in the end, and hammered or machined into the metal, to achieve a very highly polished dimpling effect that looks like the metal surface is 'sparkling'.
Textures made with metal.
- Granulation: Granulation is a technique where small granules of metal are made and soldered or fused to a metal surface. This technique has been used since ancient times. It is a beautiful finish and will wear like any other soldered or fused metal.
- Cast textures: Some more dramatic textures and markings can often be achieved through textured wax or objects that have been cast and then appropriated for use in jewellery.
- Reticulation: Reticulation is process where the surface of the metal is melted, and depending on the carat of the metal, will achieve a flowing and almost landscape type effect.
Surface treatments
- Oxidisation: Oxidisation is a popular finish that blackens the surface of the metal. The metal is immersed into the solution and becomes oxidised. The treatment can be long wearing but can wear off more quickly when in constant contact with abrasives and other metal, but can be easily reapplied at most jewellers.
- Anodising: Anodising is a process that uses specialised equipment and solutions to apply colour into the surface of some metals. Usually an industrial practice, anodising is mostly used on aluminium and titanium in the jewellery industry. Anodising, being a surface treatment only, can be scratched off when in contact with abrasives and other metals.
- Titanium colouring: As mentioned previously, titanium can be coloured through anodising. It can also be coloured through heat. Titanium can be coloured from straw yellow to purple and blues. As with any surface treatment, the colour can be scratched off when in contact with abrasives and other metals.
- Powder-coating: Powder-coating is a hardwearing treatment often used in industrial applications. The process uses a powder that is a mixture of finely ground particles of pigment and resin, which is sprayed onto a surface electrostatically. The charged powder particles adhere to the electrically grounded surfaces until heated and fused into a smooth coating in a curing oven. Powder coating comes in an array of colours from bright hues to more darker tones. Powder coating is a long wearing surface treatment.
- Enamelling: Enamelling is a technique that uses finely ground coloured glass, which is melted under high temperatures (1300-1500 degrees celsius) to adhere and meld to the metal. This a beautiful and very old technique. It is however, very delicate and must be worn with care. Any significant force, knocking or change in the metal shape may cause damage to the enamel.
- Cold Enamelling: Cold enamelling is the process of applying colour to the metal and sealing it with a glass like substance. Cold enamel is an epoxy resin and does not require heating with a kiln or a torch. Care is still needed when wearing jewellery with cold enamel treatments.
