Gold

General info

Gold is the classic rich, warm color that has been used for centuries to create pieces of value. Gold can be made in yellow, white, or rose and is suitable for most fine jewelry applications. Gold is also formulated in different karat weights. The higher the karat weight, the higher the gold content, the more yellow the gold is, the heavier the gold is, and the more soft and malleable the gold is. 14k gold provides the “best of all worlds” in that it is more than half gold content, durable, and is more affordable than the higher karat golds. Gold is a good choice for designs that are all but the most structurally delicate, and designs with engraving, milgrain, and filigree; however, over the lifetime of a ring, gold will microscopically flake off as it comes in contact with hard surfaces, causing the ring to lose metal weight and show wear in some areas. Repairs to shank, prongs, engraving & milgrain details can be expected--how soon or how often depends on the wearer’s lifestyle. Also, certain alloys in gold have been known to cause some skin allergies. If allergies are a consideration, gold can be plated with Rhodium.

Technical

A malleable precious metal, yellowish in tone, noted as Au on the periodic table. Pure gold is very soft and must be alloyed with other metals, such as copper, silver, zinc, silicon, and nickel, to gain workable strength and achieve various colors. 24k gold is 99.9% pure gold throughout, 18k gold is 75% gold throughout, and 14k gold is 58% gold throughout. 14k gold is the most durable for jewelry making. Gold does not react with most chemicals, but it is affected by chlorine, fluorine, aqua regia and cyanide.

Platinum

General info

Platinum is grayish white, heavy, and very durable. Unlike gold, platinum will not lose metal weight over time, though some repairs to platinum can be expected over time, just due to normal wear. Platinum will take dings and scratches and wear to a dull finish over time. Platinum is the recommended metal for filigree and detail work that requires strength. It is very rare for platinum to cause skin allergies.

Technical

Platinum is the most commonly used of the Platinum group of metals. (Ruthenium, Rhodium, Palladium, Osmium & Iridium & Platinum)
Platinum (Pt) is a grayish-white metal. It has a high fusion point, is malleable & ductile, expands slightly upon heating and has high electrical resistance. It is a chemically inert metal and resists attack by air, water, single acids and ordinary reagents.  Platinum melts at about 1772 °C (about 3222oF), boils at about 3827 °C (6921 °F) and has a specific gravity of about 21.45. Platinums' atomic weight is 195.09 giving it high density.
The properties of platinum group metals are ideal for jewelry (although, like gold and silver, pure platinum is too soft to be used by itself). In its pure form, platinum is harder than pure gold or silver. Because platinum is usually alloyed with other platinum group metals, it retains its density and it's resistance to corrosion. It has little or no "memory", which means that, if it is bent, it doesn't spring back to its original position. This makes platinum ideal for prong settings and other delicate work.

Platinum is a little less malleable than gold and silver, and feels a bit “gummy” when filing and drilling. This makes working platinum, and to a lesser extent Palladium- (drilling, sawing, polishing)-more difficult.
 
Platinum has to be annealed often when it is worked. Cold working distorts the metal's crystal structure, and the crystals become elongated and compressed. Annealing (heating the metal until it's just below its melting point and holding the temp for a short time) reverses that process and the crystals realign themselves.
 
Platinum's low heat conductivity keeps the heat from the torch from spreading. Platinum's higher melting temperature makes it a bit more challenging to cast too, because tends to “freeze up” quickly. The larger the piece, the Harder it is to cast, so designs that can be assembled from several small castings, rather than one or two large often work out better. Working in platinum requires different skills than the basic goldsmith learns in school. Making and repairing platinum jewelry is more complicated, more difficult and more expensive than working in silver or gold. There are, however, some intrinsic savings, as Platinum prongs rarely need re-tipping or replacing.

950 Palladium

General info

Palladium is taupe-gray in tone. Palladium is a very rare metal, and gives a similar look to platinum, at about 20% of the cost to make the same piece in platinum. Palladium is reputed to wear similarly to platinum, though it is slightly more malleable and not recommended for the most delicate or structurally difficult designs. It is very rare for palladium to cause skin allergies.

Technical

A malleable precious metal, grayish white in tone, noted as Pd on the periodic table. Palladium is a cousin to platinum with very similar chemical properties.
 

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