Art deco tortoise shell necklace 1920s

Tortoise shell and its imitations

For the modern collector, the turtle shell has become a rather exotic material. But jewelry and other objects have been formed for more than two centuries, when it was a popular decorative material, and it can still be seen on the market.

The beginning of the use of the tortoise shell dates back to dynastic Egypt, at least 3500–3100 BC. e. (dishes, combs, bracelets). Tortoise shell was popular both among the ancient Greeks and wealthy citizens of Ancient Rome. Commercial exploitation of this material in Europe began as early as the 15th century in Spain (inserts, eyeglass frames, decorative boxes, rings, bracelets, earrings, as inlay in "Bull" furniture of the 17th-18th centuries). In Japan, shell making has been an important industry since at least the 17th century, with the largest center in Nagasaki.

Turtle shell hair fork, Japan 1950-60s

The popularity of turtle shell jewelry grew rapidly during the 18th century. At the beginning of the 20th century, these animals began to be hunted almost to extinction, which led to a worldwide ban on international trade in turtle shell products from the 1970s.

Tortoise shell is composed of ß-keratin, an insoluble protein, and is almost identical in composition to hair and nail.

Imitations of tortoise shell first appeared after the development of artificial plastics in the 19th century.

The first semi-synthetic plastic, and the first material used to imitate tortoise shell, was cellulose nitrate, also known as Celluloid, which was invented in 1862 by Alexander Parkes. In 1892, cellulose acetate was developed by Cross, Bevan, and Beadle.  Around the same time, in 1897, casein formaldehyde was invented by Adolf Spitteler. Bakelite, invented and patented around 1907 by Leo Baekeland. Many of the other plastics commonly used for imitating tortoise shell, such as polyester, were developed between 1930 and 1950.

The application of standard gemological testing methods allows the unambiguous distinction tortoise shell from its imitations. Typically, tortoise shell can be readily identified by microscopy and luminescence techniques.

The horn may be very similar in overall appearance to the blond shell of a turtle, but the structure of the horn is dramatically different as it is quite fibrous.

Turtle shell cuff links and tie clip, Japan 1950-1960s

The most accessible method for identification is the "hot spot" (although not always appropriate). Tortoise and horn have the smell of burnt hair, casein - curdled milk, celluloid - camphor, modern plastics - phenol.

 

 

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