Mood ring
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A mood ring is a finger ring that contains a thermochromic element, or "mood stone", that changes colors based on the temperature of the finger of the wearer. Finger temperature, as long as the ambient temperature is relatively constant, is significantly determined by peripheral blood flow. A mood ring contains liquid crystals that change color depending on the temperature.<ref name="marechal">Template:Cite book</ref>
HistoryEdit
The idea to use thermosensitive elements in jewelry first arose from the American jeweler Marvin Wernick in 1974 after reading a magazine article about the use of liquid crystal elements in medical thermometers.Template:Sfn He found a compound that changed color from black to green, blue and deep blue in the range of 32–38 °C and in January 1975 developed a technique for using it in pendants and rings.Template:Sfn Sales began in February. Wernick called the jewelry "magical", and his promotional materials claimed that the color of the pendant or ring is an indicator of the warmth of the wearer's character.Template:Sfn Since Wernick did not patent the invention, other jewelers adopted the idea and began to produce their thermosensitive jewelry. Soon someone came up with a successful term "mood ring", which was quickly adopted by all manufacturers, including Wernick.Template:Sfn
Important producers of "mood rings" were Joshua Reynolds and Maris Ambats; many sources credit them as their inventor.Template:Sfn Reynolds called the rings "a real biofeedback tool" that allows a person to get additional information about their body.Template:Sfn In December 1975 the total value of the rings sold reached $15 million.Template:Sfn However, in mid-December, the demand for rings suddenly fell as the market was oversaturated, and companies that did not have time to sell rings suffered losses.Template:Sfn After a couple of years, "mood rings" went out of fashion.Template:Sfn