A tension ring is a type of finger ring that holds a gemstone in place by pressure rather than prongs, a bezel or other mounting. The metal setting is actually spring-loaded to exert pressure onto the gemstone, and tiny etchings or grooves in the metal create a shelf that supports the gemstone's edges. The gemstone appears to be suspended in the air with nothing holding it in place.
A major difference between tension settings and other settings is that tension settings are manufactured only after they are sold while other settings are often manufactured first and then sold to consumers. There are several reasons for this difference. First, tension settings can not be resized easily, as resizing removes the spring-loading effect. In some designs, they can be resized up or down up to 2 sizes. Sometimes, instead of resizing a tension setting, the manufacturer actually melts down the old setting and creates a new spring-loaded tension setting that is appropriately sized. Second, tension settings are calibrated to the exact specifications of the stone that they hold, therefore they cannot be manufactured until the customer has selected a gem. Unlike other settings, which can be manufactured ahead of time regardless of the stone they ultimately hold, each tension setting is designed for a specific stone. The tension setting is calibrated by a computer, using light to identify the exact places the mount must apply pressure on the gemstone to avoid fracturing it through uneven pressure distribution.
Because tension settings place such pressure on the stone, only four types of gemstone can be placed in a tension setting safely: diamonds, rubies, moissanite, and sapphires. Additionally, tension setting manufacturers must be careful which stones they place in tension settings. A stone that either has significant inclusions or is too soft may fracture under the intense pressure of the setting. The Mohs scale is a reliable way to rank a gem's hardness. Generally gems with a Mohs hardness of less than 9.0 are not suitable for tension mounting.
The term "tension setting" is, from the physical science perspective, a misnomer. The stone is not held in tension (a pulling force) but in fact in compression (a pressing force).
A tension ring is a robust assembly, generally exerting around 12,000 pounds per square inch of pressure. To make a tension setting, the manufacturer must harden the metal, use special alloys, and pressure treat the metal to create the strength required for the spring-loaded structure. The jeweler cold-works and hardens the metal before setting the gem.
Some tension rings exert up to 50,000 psi (350 MPa) on the diamond. It is not possible to exert so great a pressure on a stone with a Mohs scale of mineral hardness rating of less than 9.0. Furthermore, to exert this pressure on a gem, particularly one of high importance, the maker must ensure even pressure distribution. This requires careful calculation, and inspection of the gem to ensure that every facet mates perfectly with the ring.
Tension rings are also manufactured using other metals, particularly those that are naturally strong, such as titanium or stainless steel. These materials do not require special alloying or manufacturing processes for the creation of a tension ring. In these cases, a stone can be set as-cast with relative ease. These materials are usually used for "fashion" jewelry, and are set with small diamonds or semi-precious gems such as topaz or tourmaline. However, there is a growing group of artists using titanium to produce high value handmade tension rings
There are conflicting perspectives regarding the security of tension settings. Many jewelers contend that tension settings are as safe and potentially safer than four and six prong settings, but there are others who contend that prongs are stronger. The reality is that both ring designs have weaknesses that are unique to their engineering process. Prongs can snag on clothes and other loose objects, and they weaken with time and usage. As a result, prongs must be repaired or replaced periodically. On the other hand, tension settings do not lose their spring-loading over time, so the stone does not fall out as a result of the setting weakening. Critics do contend that a stone can potentially be dislodged from a tension setting if it is hit hard enough or if the setting is damaged to the point where its spring loading is compromised. Tension manufacturers partially agree with this statement, warning their customers that stones can be lost if the setting suffers a blunt force impact that damages the spring-loading, but they also point out that no stone has ever been lost as a result of a manufacturing defect.[ citation needed ] There is a risk that the setting can be compromised by a high impact. This, however, is also true of prong settings, and cases of prongs failing and stones falling out are common. Tension settings on the other hand do not need to be replaced, and unless the spring-loading is damaged, are unlikely to lose a gem stone.
Some rings, while advertised as and having the appearance of tension rings, in fact have a bridge holding the ring together underneath the jewel. These are not true examples of a tension set ring, but are a good affordable alternative to true tension settings. Though the wearer knows it is not a true tension setting, it looks like one to the casual observer. This is also a good option for a mass produced ring.
The first tension ring, called the Niessing Spannring, was created in 1979 by the German company Niessing. [1] However, the general concept of tension settings has been around for over 40 years as it was developed in the late 1960s by a Niessing employee named Friedrich Becker.
The original Niessing tension ring was constructed out of 18 karat gold (75% pure gold and 25% other alloying metals) and weighed 35 grams. The alloys in the 18 karat blend were non traditional jewelry metals, used to give the ring much greater strength than normal. In 1987, Steven Kretchmer patented a proprietary platinum alloy called "Plat/SK". This has since been licensed to other companies, for example Hoover & Strong, who require a super hard platinum alloy for jewelry such as tension set rings. Steven Kretchmer's advancements in the alloying of metals allowed the modern day tension ring to lose much of its weight without sacrificing strength.
Currently, Steven Kretchmer holds two patents (5,084,108 and 5,188,679) for the tension-set ring. [2] Patent 5,084,108, issued January 28, 1992, is for a method for forming metal compression-spring gemstone mounting. [3] Patent 5,188,679 is for the actual metal compression-spring gemstone mounting, i.e., the outcome of the method patented by Kretchmer. [4] The first online retail jeweler, for Steven Kretchmer's tension set rings, was Pearlman's Jewelers.
Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α- a-, "not" and μεθύσκω methysko / μεθώ metho, "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.
A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks and occasionally organic materials that are not minerals are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity and notoriety are other characteristics that lend value to gemstones.
Jewellery or jewelry consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a western perspective, the term is restricted to durable ornaments, excluding flowers for example. For many centuries metal such as gold often combined with gemstones, has been the normal material for jewellery, but other materials such as glass, shells and other plant materials may be used.
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphirus" from the Greek "sappheiros", which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.
Lapidary is the practice of shaping stone, minerals, or gemstones into decorative items such as cabochons, engraved gems, and faceted designs. A person who practices lapidary is known as a lapidarist. A lapidarist uses the lapidary techniques of cutting, grinding, and polishing. Hardstone carving requires specialized carving techniques.
Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.
A spring is a device consisting of an elastic but largely rigid material bent or molded into a form that can return into shape after being compressed or extended. Springs can store energy when compressed. In everyday use the term often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel. An example of a non-metallic spring is the bow, made traditionally of flexible yew wood, which when drawn stores energy to propel an arrow.
The most common type of spring is the coil spring, which is made out of a long piece of metal that is wound around itself. Coil springs were in use in Roman times, evidence of this can be found in bronze Fibulae — the clasps worn by Roman soldiers among others. These are quite commonly found in Roman archeological digs.
A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. It is a deformable material that is used to create a static seal and maintain that seal under various operating conditions in a mechanical assembly.
A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the tail. On installation, the rivet is placed in a punched or drilled hole, and the tail is upset or bucked, so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place. In other words, the pounding or pulling creates a new "head" on the tail end by smashing the "tail" material flatter, resulting in a rivet that is roughly a dumbbell shape. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head or buck-tail.
Grinding wheels are wheels that contain abrasive compounds for grinding and abrasive machining operations. Such wheels are also used in grinding machines.
A piston ring is a metallic split ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine.
In materials science, hardness is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter.
A garter spring is a coiled steel spring that is connected at each end to create a circular shape, and is used in oil seals, shaft seals, belt-driven motors, and electrical connectors. Compression garter springs exert outward radial forces, while extension garter springs exert inward radial forces. The manufacturing process is not much different from the creation of regular coiled springs, with the addition of joining the ends together. Like most other springs, garter springs are typically manufactured with either carbon steel or stainless steel wire.
A bench jeweler is an artisan who uses a combination of skills to make and repair jewelry. Some of the more common skills that a bench jeweler might employ include antique restoration, silversmith, Goldsmith, stone setting, engraving, fabrication, wax carving, lost-wax casting, electroplating, forging, and polishing.
Stonesetting is the art of securely setting or attaching gemstones into jewelry.
Prong setting or prong mount refers to the use of metal projections or tines, called "prongs", to secure a gemstone to a piece of jewelry. A prong setting is one component of what is known to jewelers as a head, a claw-shaped type of binding that is welded or soldered to a jewelry item to mount a gemstone to the jewelry item. A common setting for diamond engagement rings, the prong setting allows light to strike a gemstone from more angles, increasing its brilliance.
A bezel is a wider and usually thicker section of the hoop of a ring, which may contain a gem or a flat surface. Rings are normally worn to display bezels on the upper or outer side of the finger. In gem-cutting the term bezel is used for those sloping facets of a cut stone that surround the flat table face, which is the large, horizontal facet on the top.
Diamond is one of the best-known and most sought-after gemstones. They have been used as decorative items since ancient times.