Uses of Silver
Silver is leading a revolution in technology and medicine. The white metal's unique bacteria-fighting qualities are becoming more and more critical in healing conditions ranging from severe burns to Legionnaires Disease. In fact, the most powerful treatment for burns is silver sulfadiazine, which is used in every hospital in North America to promote healing and reduce infection. Everything from surgical threads to bandages and dressings to doctors' coats and catheters are utilizing silver. In hospitals and homes, silver in ductwork provides maximum sterile atmosphere.
Silver is the best electrical conductor of all metals. Because it does not corrode, its use in electrical and motor control switches is universal. A fully-equipped automobile may have over 40 silver-tipped switches to start the engine, activate power steering, brakes, windows, mirrors, locks and other electrical accessories
Silver is also one of the few elements that improve the efficiency of chemical reactions. It is the only catalyst that will oxidize ethylene gas into ethylene oxide, the building block for polyester textiles used for clothing and specialty fabrics, and melded items like computer keyboards, electrical control knobs, domestic appliance components and Mylar tape used for all audio, VCR and recording tapes. Nanotechnology applications using silver are growing -- in computers, communications, miniature motors and switches.
Silvered windshields in homes, cars and office buildings reflect away some 70% of the solar energy that would otherwise pass through, thus reducing the load on air conditioners. The U.S. Department of Energy's Energy Star Program has spurred 50% increase in silver-coated glass in past six years, translating to 350 million square feet of glass, or five million ounces of silver per year.
Silver is the ideal industrial material. No other metal has silver's combined strength, malleability and ductility, or facilitates electrical and thermal conductivity as well, or can reflect light and endure such extreme temperature changes. Jet engines of today and tomorrow can depend on silver-coated bearings for their performance and safety. All major jet engine manufacturers utilize these high-performance silver bearings, which provide critical fail-safe lubrication required by the Federal Aviation Administration.
Printed circuit boards (PCBs) use silver for connecting paths of electronic circuitry. PCBs are essential to the electronics that control the operation of aircraft, automobile engines, electrical appliances, security systems, telecommunication networks, mobile telephones, television receivers. Most computer keyboards use silver membrane switches.
These low-current switches are also found in control panels of cable television, telephones, and devices using digital electronics. Superconductivity is the power transmission of the future and silver makes it faster and more effective. Silver-jacketed superconducting oxide wires can carry more than 140 times the electric load of copper wire with less than 1 percent of the weight. This wire utilizes about 1,000 ounces of silver per mile. Silver already improves performance at lighter weights and size in cables, motors, generators and transformers. Silver oxide-zinc batteries provide higher voltages and longer life for such consumer goods as quartz watches, cameras, and electronic tools.
The ease of electrodeposition of silver accounts for silver's widespread use in coating. The plating thickness of some items, such as fuse caps, is less than one micron although the silver then tarnishes more easily. Coatings of two to seven microns are normal for heavy duty electrical equipment. Silver plating is used in a wide variety of applications from Christmas Tree ornaments to cutlery and hollowware.
Silver facilitates the joining of materials (called brazing when done at temperatures above 600oCelsius and soldering when below) and produces naturally smooth, leak-tight and corrosion-resistant joints. Silver brazing alloys are used widely in applications ranging from air-conditioning and refrigeration equipment to power distribution equipment in the electrical engineering sector. It is also used in the automobile and aerospace industries.
Silver, being a rare and noble metal, was a more desirable medium of exchange than beads, feathers, shells, and the like. Its use as a medium of exchange is known throughout all recorded history. Coins, in the sense of having an authenticating stamp on them, began to appear in the eastern Mediterranean during 550 B.C. By 269 B.C. Rome adopted silver as part of its standard coinage. Silver became the trading medium for merchants throughout the civilized world. (Gold being reserved for governments and the wealthy.) Today silver coins continue to be the medium of exchange wherever paper is not acceptable, for example, in parts of Africa and the Middle East. One example of a trade coin is the Empress Maria Theresia Taler, first minted in Austria in 1741. It was standardized in 1780 as 28 grams and 833/1000 silver (the remainder copper). Some 370 million of these 1780 dated coins have been minted up to 1996 and a large proportion remain in circulation today.
Although a wide variety of other technology is available, silver-based photography will retain its pre-eminence due to its superior definition and low cost. From it's very outset, silver halide has been the material that records what is to be seen in the photograph. As little as 4 photons of light activate silver halides which amplify that incident light by a factor of one billion times. In today's photography, silver halides are coupled with dyes that bring the color of the world around us into permanent record. An estimated 196 million troy ounces of silver were used worldwide in 2003 for photographic purpose.
Silver possesses working qualities similar to gold but enjoys greater reflectivity and can achieve the most brilliant polish of any metal. To make it durable for jewelry, however, pure silver (999 fineness) is often alloyed with small quantities of copper. In many countries, Sterling Silver (92.5% silver, 7.5% copper) is the standard for silverware and has been since the 14th century.
Silver's unique optical reflectivity, and its property of being virtually 100% reflective after polishing, allows it to be used both in mirrors and in coatings for glass, cellophane or metals. Everyone is accustomed to silvered mirrors. What is new is invisible silver, a transparent coating of silver on double pane thermal windows. This coating not only rejects the hot summer sun, but also reflects inward internal house heat. A new double layer of silver on glass marketed as "low E squared" is sweeping the window market as it reflects away almost 95% of the hot rays of the sun, creating a new level of household energy savings. Over 250 million square feet of silver- coated glass is used for domestic windows in the U.S. yearly and much more for silver coated polyester sheet for retrofitting windows.
Silver paste is used in 90 percent of all crystalline silicon photovoltaic cells, which are the most common solar cell, according to the Photovoltaic Technology Division of the U.S. Department of Energy. And all silicon cells used in space to power satellites use silver in the form of evaporated metal to make the electrical contact. The electricity generated by photovoltaic cells is highly reliable. As soon as sunlight strikes, power begins to flow. Sunlight striking silicon cells generates electrons, which the silver conductors collect to become a useful electric current. The conductive silver, which also enhances reflection of the sunlight, is applied in the form of a glass paste with a minimum of 90 percent silver along the top and across the bottom of the silicon crystal. When fired, the silver forms a complete circuit collecting solar energy and conducting it to the power supply line. A group of roofing-tile solar cells can generate sufficient power to provide a house and also fill batteries to supply power after dark. Silver plays yet another role in the collection of solar energy: efficient reflection of solar heat. Silver is the best reflector of thermal energy (after gold).
An increasing trend is the millions of on-the-counter and under-the-counter water purifiers that are sold each year in the United States to rid drinking water of bacteria, chlorine, trihalomethanes, lead, particulates, and odor. Here silver is used to prevent the buildup of bacteria and algae in the filters. Of the billions of dollars spent yearly in the U.S. for drinking water purification systems, over half make advantageous use of the bactericidal properties of silver. New research has shown that the catalytic action of silver, in concert with oxygen, provides a powerful sanitizer, virtually eliminating the need for the use of corrosive chlorine.