Tension ring
Encyclopedia
A tension ring is a type of finger ring
in which the gemstone is held 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/grooves are added to the metal in order to create a shelf for the gemstone's edges to rest. The gemstone appears to be suspended in the air with nothing holding it in place.
Because tension settings place such pressure on the stone, only three types of gemstone can be placed in a tension setting: diamonds, rubies, 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 will fracture under the intense pressure of the setting. The Mohs scale
is a reliable way to rank a gem's hardness; generally gems that have a Mohs hardness of less than 9.0 cannot be placed in the setting.
It should also be noted that the term "tension setting" is, from the perspective of physical science, a misnomer. The stone is not held in tension (a pulling force) but in fact in compression (a pressing force.) The ring however is placed in tension by the presence of the stone.
Currently,Gelin & Abaci and Steven Kretchmer produce the strongest clamping tension rings. These 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, in order to exert this pressure on a gem, particularly one of high importance, the maker must ensure the even distribution of pressure upon it. 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
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(tm) ring. Patent 5,084,108, issued January 28, 1992, is for a method for forming metal compression-spring gemstone mounting. Patent 5,188,679 is for the actual metal compression-spring gemstone mounting, i.e., the outcome of the method patented by Kretchmer. No other manufacturer in the United States currently holds a patent for a tension setting ring or component.
Ring (finger)
A finger ring is a circular band worn as a type of ornamental jewelry around a finger; it is the most common current meaning of the word ring. Other types of metal bands worn as ornaments are also called rings, such as arm rings and neck rings....
in which the gemstone is held 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/grooves are added to the metal in order to create a shelf for the gemstone's edges to rest. The gemstone appears to be suspended in the air with nothing holding it in place.
Characteristics
A major difference between tension settings and other settings is that tension settings are only manufactured 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 them will remove the spring-loading effect. Instead of resizing a tension setting, the manufacturer actually has to melt down the old setting and create a new spring-loaded tension setting that is appropriately sized. Second, tension settings are calibrated to the exact specifications of the stone that they will hold, therefore they can not be manufactured until the customer has selected the gem that will go inside. Unlike other settings which can be manufactured ahead of time regardless of the stone that will ultimately be placed inside, each tension setting is designed specifically for the stone it will hold. The tension setting is calibrated by a computer using light to identify the exact places where pressure must be applied on the gemstone in order to avoid fracturing it through even pressure distribution.Because tension settings place such pressure on the stone, only three types of gemstone can be placed in a tension setting: diamonds, rubies, 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 will fracture under the intense pressure of the setting. The Mohs scale
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
is a reliable way to rank a gem's hardness; generally gems that have a Mohs hardness of less than 9.0 cannot be placed in the setting.
It should also be noted that the term "tension setting" is, from the perspective of physical science, a misnomer. The stone is not held in tension (a pulling force) but in fact in compression (a pressing force.) The ring however is placed in tension by the presence of the stone.
Technical Information
A tension ring is a very robust construct, generally exerting around 12,000 pounds of pressure per square inch. In-order to make a tension setting, the manufacturer must work to harden the metal, employ special alloys, and pressure treat the metal to create the super strength that is required for the springloading process to occur. Having undergone special alloying, hardening and other treatment processes to increase its strength. When the ring is being made, the metal is cold-worked and hardened before setting the gem, then heat-treated for additional hardness once the gem is set.Currently,Gelin & Abaci and Steven Kretchmer produce the strongest clamping tension rings. These rings exert up to 50,000 psi
Pounds per square inch
The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...
(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
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
rating of less than 9.0. Furthermore, in order to exert this pressure on a gem, particularly one of high importance, the maker must ensure the even distribution of pressure upon it. 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
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
. 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
Tension Setting Security Debate
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 will not lose their spring-loading over time, and the stone will therefore 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. Overall, there is a risk that the setting can be compromised when exposed to high impact, but this is also true of prong settings and there are many examples of prongs failing and needing to be replaced. Tension settings on the other hand do not need to be replaced, and unless their spring-loading is damaged, are very unlikely to lose their gem stone.Faux Tension Settings
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 they are a good option if you are looking for an affordable alternative to true tension settings. Although the wearer knows that it is not a true setting, it will appear to be a tension setting to the casual observer.History
The first tension ring, called the „Niessing Spannring®", was created in 1979 by the German company Niessing. 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 tension ring designs were very bulky in order to provide the strength to maintain sufficient pressure on the suspended stone. These early rings are so bulky that they resemble a solid metal inner tube wrapped around the finger. Steven Kretchmer was the first American adoptee of this design, and perfected the work hardening process that allowed his ring designs to be less heavy than the Niessing originals without sacrificing strength. Other ring designers followed Kretchmer's adaptations within a few years.The original Niessing tension ring was constructed out of 18 karat gold (75% pure gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
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
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
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(tm) ring. Patent 5,084,108, issued January 28, 1992, is for a method for forming metal compression-spring gemstone mounting. Patent 5,188,679 is for the actual metal compression-spring gemstone mounting, i.e., the outcome of the method patented by Kretchmer. No other manufacturer in the United States currently holds a patent for a tension setting ring or component.
Tension Ring Companies
Currently Niessing, Kretchmer, Sareenjewelry , Danhov Gelin & Abaci are the industry leaders in tension ring production. Gelin & Abaci is the largest producer in the world.External links
- Common Tension Settings Rothem Collection
- http://www.whiteflash.com/about-diamonds/tips-and-advice/guide-to-diamond-settings-the-tension-setting-779.htmA Guide to Tension Settings