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About Metals

We find that working with brass, as well as metals in general, is a fascinating business. We learn something new every day! For definitions of some of the metals-related terms we have used in this Web (and some we haven't), please click the link titles below.

 

About Silver - Click Here

Silver is a chemical element with the symbol "Ag" (Latin: argentum, from the Ancient Greek: argēntos, gen. of argēeis, "white, shining") and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. It occurs as a pure free metal (native silver) and alloyed with gold, as well as in various minerals, such as argentite and chlorargyrite. Most silver is produced as a by-product of copper, gold, lead, and zinc mining.

Silver has been known since ancient times and has long been valued as a precious metal, used to make ornaments, jewellery, high-value tableware and utensils (hence the term "silverware") and currency coins. Today, silver metal is used in electrical contacts and conductors, in mirrors and in catalysis of chemical reactions. Its compounds are used in photographic film and dilute solutions of silver nitrate and other silver compounds are used as disinfectants. Although the antimicrobial uses of silver have largely been supplanted by the use of antibiotics, its antiseptic properties are still a useful tool in the prevention and treatment of sepsis and infections caused by antibiotic-resistant microorganisms such as MRSA.

Silver is found in native form, alloyed with gold or combined with sulfur, arsenic, antimony or chlorine in ores such as argentite (Ag2S), horn silver (AgCl), and pyrargyrite (Ag3SbS3). The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from Peru, Mexico, China, Australia, Chile and Poland. Peru and Mexico have been mining silver since 1546 and are still major world producers. Top silver producing mines are Proano / Fresnillo, Cannington, Dukat, Uchucchacua and Greens Creek mine.

The metal can also be produced during the electrolytic refining of copper and by the application of the Parkes process on lead metal obtained from lead ores that contain small amounts of silver. Commercial-grade fine silver is at least 99.9% pure silver, and purities greater than 99.999% are available. In 2007, Peru was the world's top producer of silver, closely followed by Mexico, according to the British Geological Survey.

Silver is a very ductile and malleable (slightly harder than gold) monovalent coinage metal with a brilliant white metallic luster that can take a high degree of polish. It has the highest electrical conductivity of all metals, even higher than copper, but its greater cost and tarnishability have prevented it from being widely used in place of copper for electrical purposes, though it was used in the electromagnets used for enriching uranium during World War II (mainly because of the wartime shortage of copper). Another notable exception is in high-end audio cables, although the actual benefits of its use in this application are questionable.

Among metals, pure silver has the highest thermal conductivity (only the non-metal diamond's is higher), the whitest color, and the highest optical reflectivity (although aluminium slightly outdoes it in parts of the visible spectrum, and it is a poor reflector of ultraviolet light). Silver also has the lowest contact resistance of any metal. Silver halides are photosensitive and are remarkable for their ability to record a latent image that can later be developed chemically. Silver is stable in pure air and water, but tarnishes when it is exposed to air or water containing ozone or hydrogen sulfide. The most common oxidation state of silver is +1 (for example, silver nitrate: AgNO3); in addition, +2 compounds (for example, silver(II) fluoride: AgF2) and +3 compounds (for example, potassium tetrafluoroargentate: K[AgF4]) are known.

As a precious metal

A major use of silver is as a precious metal and it has long been used for making high-value objects reflecting the wealth and status of the owner. Jewellery and silverware are traditionally made from sterling silver (standard silver), an alloy of 92.5% silver with 7.5% copper. Sterling silver is harder than pure silver and has a lower melting point (893 °C) than either pure silver or pure copper. Britannia silver is an alternative hallmark-quality standard containing 95.8% silver, often used to make silver tableware and wrought plate. With the addition of germanium, the patented modified alloy Argentium Sterling Silver is formed, with improved properties including resistance to firescale.

Silver is used in medals, denoting second place. Some high-end musical instruments, such as the flute, are made from sterling silver.

About Brass - Click Here

Brass is any alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.  In comparison, bronze is principally an alloy of copper and tin. Despite this distinction, some types of brasses are called bronzes. Brass is a substitutional alloy. It is used for decoration for its bright gold-like appearance; for applications where low friction is required such as locks, gears, bearings, ammunition, and valves; for plumbing and electrical applications; and extensively in musical instruments such as horns and bells for its acoustic properties.

Brass has a muted yellow color, somewhat similar to gold. It is relatively resistant to tarnishing, and is often used as decoration and for coins.

Brass has likely been known to humans since prehistoric times, even before zinc itself was discovered. It was produced by melting copper together with calamine, a zinc ore. In the German village of Breinigerberg an ancient Roman settlement was discovered where a calamine ore mine existed. During the melting process, the zinc is extracted from the calamine and mixes with the copper. Pure zinc, on the other hand, has too low a boiling point to have been produced by ancient metalworking techniques. The many references to “brass” appearing throughout the King James Bible are thought to signify another bronze alloy, or copper, rather than the strict modern definition of brass.

About Copper - Click Here

Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with excellent electrical conductivity, rather soft in its pure state, and has a pinkish luster which is (besides gold) unusual for metals which are normally silvery white. It finds extensive use as an electrical conductor, heat conductor, as a building material, and as a component of various alloys.

Copper is an essential trace nutrient to all high plants and animals. In animals, including humans, it is found primarily in the bloodstream, as a co-factor in various enzymes, and in copper-based pigments. However, in sufficient amounts, copper can be poisonous and even fatal to organisms.

Copper has played a significant part in the history of humankind, which has used the easily accessible uncompounded metal for thousands of years. Several early civilizations have early evidence of using copper. During the Roman Empire, copper was principally mined on Cyprus, hence the origin of the name of the metal as Cyprium, "metal of Cyprus," later shortened to Cuprum.

A number of countries, such as Chile and the United States, still have sizable reserves of the metal which are extracted through large open pit mines; however, like tin, there may be insufficient reserves to sustain current rates of consumption. High demand relative to supply has caused a price spike in the 2000s.

Copper also has a significant presence as a decorative metal art. It can also be used as an anti-germ surface that can add to the anti-bacterial and antimicrobial features of buildings such as hospitals.

About Gold - Click Here

Gold is a chemical element with the symbol Au (from its Latin name aurum) and atomic number 79.  It is a highly sought-after precious metal which, for many centuries, has been used as money, a store of value and in jewelry.  The metal occurs as nuggets or grains in rocks, underground "veins" and in alluvial deposits.  It is one of the coinage metals. Gold is dense, soft, shiny and the most malleable and ductile of the known metals.  Pure gold has a bright yellow color traditionally considered attractive.

Gold formed the basis for the gold standard used before the collapse of the Bretton Woods system. The ISO currency code of gold bullion is XAU.

Modern industrial uses include dentistry and electronics, where gold has traditionally found use because of its good resistance to oxidative corrosion.

Chemically, gold is a transition metal and can form trivalent and univalent cations upon solvation.  Gold does not react with most chemicals, but is attacked by chlorine, fluorine, aqua regia and cyanide.  Gold dissolves in mercury, forming amalgam alloys, but does not react with it. Gold is insoluble in nitric acid, which will dissolve silver and base metals, and this is the basis of the gold refining technique known as "inquartation and parting".  Nitric acid has long been used to confirm the presence of gold in items, and this is the origin of the colloquial term "acid test," referring to a gold standard test for genuine value.

Characteristics

Gold is the most malleable and ductile metal; a single gram can be beaten into a sheet of one square meter, or an ounce into 300 square feet.  Gold leaf can be beaten thin enough to become translucent.  The transmitted light appears greenish blue, because gold strongly reflects yellow and red.

Gold readily forms alloys with many other metals.  These alloys can be produced to increase the hardness or to create exotic colors (see below).  Gold is a good conductor of heat and electricity, and is not affected by air and most reagents.  Heat, moisture, oxygen, and most corrosive agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; conversely, halogens will chemically alter gold, and aqua regia dissolves it via formation of the chloraurate ion.

Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds).  Gold ions in solution are readily reduced and precipitated out as gold metal by adding any other metal as the reducing agent.  The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate.

Recent research undertaken by Sir Frank Reith of the Australian National University shows that microbes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits.

High quality pure metallic gold is tasteless, in keeping with its resistance to corrosion (it is metal ions which confer taste to metals).

In addition, gold is very dense, a cubic meter weighing 19300 kg. By comparison, the density of lead is 11340 kg/m³, and the densest element, iridium, is 22650 kg/m³.

Color

The usual gray color of metals depends on their "electron sea" that is capable of absorbing and re-emitting photons over a wide range of frequencies. Gold behaves differently, depending on subtle relativistic effects that affect the orbitals around gold atoms.
 

About Pewter - Click Here

Use of pewter was common from the Middle Ages up until the various developments in glass-making during the 18th and 19th centuries. Pewter was the chief tableware until the making of porcelain. Mass production of glass products has seen glass universally replace pewter in day-to-day life. Pewter artefacts continue to be produced, mainly as decorative or specialty items. Pewter was also used around East Asia. Roman pewter items are very rare, although some are still in existence. Pewter gradually stopped being used and by 1850,it was just about gone. By the 20th century, however, the craft had been brought back into existence.

Unlidded mugs and lidded tankards may be the most familiar pewter artifacts from the late 17th and 18th centuries, although the metal is also used for many other items including porringers, plates, dishes, basins, spoons, measures, flagons, communion cups, teapots, sugar bowls, beer steins and cream jugs. In the early 19th century, changes of fashion witnessed a decline in the use of pewter flatware, but increased production of both cast and spun pewter tea sets, whale-oil lamps, candlesticks, etc. Later in the century, pewter alloys were often used as a base metal for silver-plated objects.

Today, pewter is mainly used in decorative objects, namely collectible statuettes and figurines, replica coins, pendants, etc.

Contrary to urban legend, the use of lead-containing pewter tableware was unrelated to the mistrust of tomatoes as a foodstuff in Northern Europe during the Middle Ages.

About Solder - Click Here

A solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C (200 to 840 °F), used in a process called soldering where it is melted to join metallic surfaces. It is especially useful in electronics and plumbing. Alloys that melt between 180 and 190 °C are the most commonly used.

The word solder comes from the Middle English word soudur, via Old French solduree and soulder, from the Latin solidare, meaning "to make solid." In North America "solder" is pronounced with a silent L. Solder can contain lead and or flux, but in most cases solder is now lead free.

Tin/lead solder

Tin/lead solders are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder’s tensile and shear strengths. At the retail level, the two most common alloys are 60/40 Sn/Pb and 63/37 Sn/Pb used principally in electrical work. The 63/37 ratio is notable in that it is a eutectic mixture, which means: 1. It has the lowest melting point (183 °C or 361.4 °F) of all the tin/lead alloys; and 2. The melting point is truly a point — not a range

At an eutectic composition, the liquid solder solidifies as a eutectic, which consists of fine grains of nearly pure lead and nearly pure tin phases, but in no way is it an intermetallic, since there are no tin/lead intermetallics, as can be seen from a tin/lead equilibrium diagram.

In plumbing, a higher proportion of lead was used. This had the advantage of making the alloy solidify more slowly, so that it could be wiped over the joint to ensure watertightness. Although lead water pipes were displaced by copper when the significance of lead poisoning began to be fully appreciated, lead solder was still used until the 1980s because it was thought that the amount of lead that could leach into water from the solder was negligible. Since even small amounts of lead have been found detrimental to health, lead in plumbing solder was replaced by copper or antimony, with silver often added, and the proportion of tin was increased (see Lead-free solder below).

Hard solder

As used for brazing, is generally a copper/zinc or copper/silver alloy, and melts at higher temperatures.

In silversmithing or jewelry making, special hard solders are used that will pass assay. They contain a high proportion of the metal being soldered and lead is not used in these alloys. These solders also come in a variety of hardnesses, known as 'enamelling', 'hard', 'medium' and 'easy'. Enamelling solder has a high melting point, close to that of the material itself, to prevent the joint desoldering during firing in the enamelling process. The remaining solder types are used in decreasing order of hardness during the process of making an item, to prevent a previously soldered seam or joint desoldering while soldering a new joint. Easy solder is also often used for repair work for the same reason. Flux or rouge is also used to prevent joints desoldering.

Silver solder is also used in manufacturing, when there is a need to join metal parts that cannot be welded. The alloys used for these purposes contain a high proportion of silver (up to 40%), and may also contain toxic cadmium.

Flux core solder

A tube of multicore electronics solder used for manual soldering — the flux is contained in five cores within the solder itself.

Solder often comes pre-mixed with, or is used with, flux, a reducing agent designed to help remove impurities (specifically oxidised metals) from the points of contact to improve the electrical connection. For convenience, solder is often manufactured as a hollow tube and filled with flux. Most cold solder is soft enough to be rolled and packaged as a coil, making for a convenient and compact solder/flux package. The two principal types of flux are acid flux, used for metal mending, and rosin flux, used in electronics, where the corrosiveness of the vapours that arise when acid flux is heated could damage components. Due to concerns over atmospheric pollution and hazardous waste disposal, the electronics industry has been gradually shifting from rosin flux to water-soluble flux, which can be removed with deionised water and detergent, instead of hydrocarbon solvents.

Lead-free solder

On July 1, 2006 the European Union Waste Electrical and Electronic Equipment Directive (WEEE) and Restriction of Hazardous Substances Directive (RoHS) came into effect prohibiting the intentional addition of lead to most consumer electronics produced in the EU. No such legislation is in place in the United States, or other countries, however manufacturers may receive tax benefits by reducing the use of lead-based solder. Lead-free solders in commercial use may contain tin, copper, silver, bismuth, indium, zinc, antimony, and traces of other metals. Most lead-free replacements for conventional Sn60/Pb40 and Sn63/Pb37 solder have melting points from 5–20 °C higher, though solders with much lower melting points are available.

Drop-in replacements for silkscreen with solder paste soldering operations are available. Minor modification to the solder pots (e.g. titanium liners and/or impellers) used in wave-soldering operations may be desired to reduce maintenance costs associated with the increased tin-scavenging effects of high tin solders. The properties of lead-free solders are not as thoroughly known and may therefore be considered less reliable in select applications, e.g. hi-rel aerospace and life-critical medical. "Tin Whiskers" were a problem with early electronic solders which were coincidentally lead-free, and lead was initially added in part to eliminate them. These problems are negligible in modern alloys, however, except in hi-rel military, aerospace-satellite and life-critical medical applications.

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