About Gold . . .
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. About Gold | Discoloring | Finishes About GoldPure gold (fine gold) is softer than pure silver but harder than tin. Its beauty and luster are unmatched by any alloyed golds. The extreme malleability, ductility, and softness of pure gold make it practically useless for jewelry applications. The addition of alloying elements (other metals) to gold are used to increase the toughness and hardness of the metal. While almost any metal can be alloyed (melted) with gold, only certain metals will not dramatically change the color or make the metal brittle. The addition of indium, for instance, turns gold purple and gives gold the workability of glass. Over time, certain percentages of gold have become legally recognized "karats." The karat indicates the amount of gold as a percentage of the total, i.e. 24 karat is 100 percent gold. Thus 14 karat is 14/24's gold or 58-1/3 percent gold. Gold standards vary around the world. In the United States, 18, 14, and 10 karat gold are the only karats allowed to be sold as karated gold. In karated gold, there is a balance of metals in the non-gold percentage. These metals provide the various colors and hardness of karated golds. Typical alloying elements and their color effect are:
Examples of the compositions of different colors are:
Adjusting the proportions of coloring agents provides the array of colors on the market. Additional metals enhance properties such as castability, grain size, hardness, corrosion resistance, color, workability, ultimate strength, and others. These additions can dramatically change the properties of the karated metal for better or worse. Knowing how the additions will affect the metal greatly enhances the possibility of a superior final product. In deep drawing of metals, it is important to have a metal which will elongate or stretch a great deal before fracturing, thus high ductility. The requirement for an earring post would be a high tensile strength (a great deal of force needed to get the material to permanently deform, bend). It is imperative to select the proper karated composition for the desired application.
Why Does Gold Discolor Fingers?Jewelry owners may think that faulty manufacturing or underkarating might be the problem when a ring "turns," blackening or discoloring the skin and clothing, or the jewelry itself. However, that is not the case. True Jewelers understand the causes, and how to prevent them. The most common reason is metallic abrasion, caused by makeup on skin or clothing. Cosmetics often contain compounds harder than the jewelry itself, which wear or rub off very tiny particles. Very finely divided metal always appears black rather than metallic, so it looks like a jet-black dust. When this dust comes into contact with absorbent surfaces such as skin or clothing, it sticks, forming a black smudge. To prevent this, you should try switching cosmetics. If this is not possible, we recommend that they remove rings and other jewelry while applying them, and clean skin areas in contact with jewelry with soap and water. Another cause is actual corrosion of the metals. Gold itself does not corrode, but its primary alloys of silver or copper will do so, forming very dark chemical compounds, under moist or wet conditions. When you perspire, fats and fatty acids released can cause corrosion of 14-karat gold, especially when exposed to warmth and air. This problem can be worse in seacoast and semitropical areas, where chlorides combine with perspiration to form a corrosive element that discolors skin. Smog fumes gradually attack jewelry and are evident as a tarnish that rubs off on the skin. We suggest that you remove jewelry often and use an absorbent powder, free of abrasives, on skin that comes into contact with jewelry. Even the design of jewelry can be an influence. Wide shanks have more surface area to contact abrasives or corrosives. Concave surfaces inside a shank form collection points that trap moisture and contaminants, also causing a type of dermatitis. We also recommend that you remove all rings before using soaps, cleaning compounds or detergents, and clean your rings frequently. As well as solving the problem, you’ll be amazed at how much better your rings look! In addition to these corrective actions, we recommend that you switch to 18-karat gold or platinum. The lower alloy content of 18-karat gold, 25%, versus almost 42%, significantly reduces the problem, and the use of platinum should eliminate it completely.
FinishesThe four standard finishes for gold are . . .
Last Revised: August 09, 2007 02:55 PM. |
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