Ivory Research: overview
We should note first of all that the general term “ivory” is also used to denote materials other than elephant tusk: it is common to see hippopotamus tooth, walrus tusk, and narwhal tusk referred to as ivory (Laufer and Pelliot, 1913). Hippo tusks can actually reach 35 cm in length and 2 kg in weight (Krzyszkowska, 1984); they have a wonderfully milky colour that never goes yellow, but high density and the large internal cavity makes hippo fang a difficult material to carve – it is only used for small decorations (Insoll, 1995). All of that having been said, it is of course best to refer specifically to elephant tusk in ivory research. The bones in the rest of the elephant skeleton do not have the distinctive line pattern either on the surface or internally (Vogel et al., 1990); the value of that material is significantly lower because its visual quality is inferior to the tusks (Cutler, 1994).
The distinctive properties of ivory are the high density and the unique internal structure. Particularly attractive is the slightly translucent light beige tone that is subconsciously associated with the skin tone of young, healthy and physically perfect people (Badruddoja, 2005). The most valuable part of the tusk is its middle, where the fine pattern of thin crossing lines is particularly well developed. The finer this pattern, the greater is the perceived quality of the tusk (Barbier et al., 2013). A similar pattern appears on mammoth tusk, and a further advantage there is that the cavity, which takes up almost half of the volume of elephant tusk, is significantly smaller and therefore the volume available for carving is greater (Valde-Nowak et al., 1987).
Due to the presence of the cavity in the elephant tusk, the parts most suitable for creating artwork are the middle and the end parts. The hollow part is used for reliefs and cut-through carving, such as openwork vases (Mitlyanskaya et al., 1996). It is not uncommon to see tusks carved as a whole, with the entire surface used up. Historical ivory research indicates that carving of that type was particularly common in China (Laufer, 1925), where craftsmen created sophisticated composite patterns and made relief carving flow into openwork carving with the results that are amazing to behold even today. Creating one such tusk sometimes required a decade of work by several masters (Francis and Vickers, 1983).
When appraising ivory items, specialists consider the smoothness and the shininess of the material (Barbier et al., 2013) – the latter property may be restored by rubbing with fine leather, silk or soft wool. Another factor that influences the price of an item made of elephant tusk is the presence of a small longitudinal channel with a dark boundary that appears when the elephant reaches maturity. The characteristic pattern and the channel are unique to the centre of the tusk (Raubenheimer, 1999, Su and Cui, 1999). The ivory derived from a recently deceased elephant has greater value than that from a long-dead animal. The so-called “dead” ivory may be distinguished from “live” ivory by its matte tint and opaque irregular spots (Edwards et al., 2005).
Ivory research: genuine and fake ivory
The high demand for objects made of ivory has created a cottage industry of craftsmen that fool inexperienced and naïve buyers by peddling cheaper materials disguised as elephant tusk (Stiles, 2015).
Historical ivory research indicates that, in early 19th century, China and Indochina became centres for the manufacturing of fake ivory crafted out of vertebrae of sharks, whales and crocodiles (Barbier et al., 2013). Anyone intending to purchase ivory objects would do well to become familiar with the most popular types of fakes (Espinoza et al., 1992).
Thankfully, fake ivory is easy to identify either visually or by touch – the item does not have the line network pattern, is soft or oily to touch, or yellows quickly.
Some producers of fake ivory bleach it in the sun and wrap it into tobacco leaves to imitate the natural patina that forms on ancient ivory carvings, but even that can only fool the least experienced buyers. Bone of other animals are not the only source of fake “ivory” – even plant material is occasionally used: hard and white seeds produced by a type of a palm tree (phytelephasmacrocarpa) that grows in South America are even called “vegetable ivory” (Barfod et al., 1990), which is marketed as suitable for vegetarians. The seed is mostly composed of cellulose rather than calcium phosphate and collagen. Each seed is approximately the size of a chicken egg, it produces small pieces of “ivory” that are smooth and easy to polish. “Vegetable ivory” is being marketed by companies running research programmes into sustainable sources of ivory (Runk, 1998). It is not, however, resistant to water or mould, being essentially a highly polymerised sugar (Timell, 1957).
Economic and historical ivory research indicates that the profits from selling fake ivory have become so great in the 19th century that its manufacturing has almost entirely displaced the production of genuine (much harder to obtain and process) ivory in some countries. One of the ways of telling genuine ivory from the multitude of fakes is to rub it with vinegar. Genuine ivory immediately goes white. However, the same applies to animal teeth, and in those cases one must rely on visual inspection: animal teeth have completely different morphology that has a few distinct layers. Peeling off of these layers is likely to be noticeable (Espinoza et al., 1992).
The development of the synthetic ivory research has led to the appearance of a large number of synthetic materials that look very similar to ivory, and even exhibit similar mechanical properties (Espinoza et al., 1992). One such material became known as “French ivory”– in reality it is a highly flammable solid mixture of celluloid and camphor originally developed to produce billiard balls (Springate, 1997). Another recent advance is “3D printed ivory” where collagen and calcium phosphate are laid out in a structure that resembles ivory by a 3D printer (Derby, 2012). While such substances might appear visually identical to ivory, they miss the same fundamental point as the manufacturers of cheap watches: at present, the real ivory is not so much a functional or even a decorative material as it is a symbol of status. Using a cheap synthetic replacement is therefore similar to using a Casio watch in place of a Rolex. It may well be just as accurate and durable, but accuracy and durability are not the point of a Rolex watch (Frank, 1999).
Ivory research: legal status of ivory
The scarcity of ivory in modern times has another reason. Following decades of conservation ivory research at the end of the previous century, the United Nations imposed a moratorium on the slaughter of elephants for their tusks, as well as a ban on the sale and purchase of items crafted from ivory in modern times (Wasser et al., 2010). Just as every other virtue-signalling prohibition since time immemorial, this has instantly raised the price of ivory, which in turn encouraged poachers to kill the elephants in even greater numbers (Bulte and Van Kooten, 1999, Lemieux and Clarke, 2009). The population of elephants in many parts of the world continues dropping, and the average age of an elephant encountered in the wild continues to decrease. This in turn has a knock-on effect on the quality of the ivory because one of the principal quality criterion for a raw tusk is its length, and it takes an elephant a long time to grow to maturity (Espinoza et al., 1992).
Some countries are trying to fight UN moratorium and to point out that controlled farm breeding (much like it happens with crocodiles and caviar producing species of fish) is the way forward. The UN occasionally listens an authorises one-off deals (Bulte and Van Kooten, 1999, Lemieux and Clarke, 2009), but the general popular sentiment is such that the complete ban on ivory acquisition and transactions is likely to stay in place until pop stars and BBC journalists read up on the basic economics of supply and demand (Han et al., 2010). That is to say, indefinitely.
Ivory research: matters of geography
Size is not the only assessment criterion for a tusk – there are other parameters that influence the price, and one of them is the geographical origin (Espinoza et al., 1992). Elephants differ greatly depending on where they live. The most valuable type of ivory comes from Guinea, Gabon, and Angola; it is called “green bone”. It has a yellow tint that becomes, over subsequent years, almost perfectly white. Tusks from other locations tend on the contrary to become more yellow. Market ivory research indicates that the type currently considered second best originates from the Cape province of South Africa, from Zanzibar, and from Muscat. Ivory from these locations has a matte surface with a slight yellow tint (Espinoza et al., 1992).
Africa is not the only supplier of elephant tusk – India has also been doing a brisk trade over the years, the profits of which did however mostly land in the pockets of the inhabitants of the British Isles. There are three principal types of Indian ivory. The first type, from Ceylon, has a slight pink or a uniquely white colour. The second type comes from Siam; it is similar to Ceylon ivory but has a different line pattern. This type of ivory is exceedingly rare on the free market and very valuable. Its distinguishing characteristic is very high density and a unique colour gradient on the cross-section of the tusk: from light brown or pink to milky white. The third type is called Bombay ivory, but it is not actually sourced from the Bombay peninsula; it derives its name from a major trading location – at some point in the past, there was a market in Bombay where ivory and items crafted from it could be purchased. However, the ivory was mostly the of the lower cost African variety (Espinoza et al., 1992).
Ivory is one of the very few materials that have a geographical location named in its honour. Ivory trade was so prominent in Africa in the 19th century, that an entire country – the Republic of Côte d’Ivoire – is named after it.
Ivory research: physical, chemical, and medical properties
Ivory is essentially calcium hydroxyl phosphate interspersed with organic matter – a chemical composition similar to that of mammalian teeth. A large body of chemical and material science work exists on the matter. Ivory appears amorphous on X-ray diffractograms, it is optically translucent with a refractive index of around 1.5, and has weak to moderate blue to violet fluorescence under UV light. Its hardness is around 2.5 on the Moos scale, its density varies between 1.7 and 2.0 grams per cubic centimetre. It has a greasy lustre and a splintery fracture (Chen et al., 2008).
Ivory is currently being used in Chinese medicine and even got patented to treat bone tuberculosis and osteomyelitis as well as hyperostosis. Serious medical ivory research indicates that it is unlikely that ground ivory has any therapeutic effect beyond simply being a source of calcium and phosphorus. Given its origin, it is not surprising that ivory had found some early use in dentistry: president Washington had prosthetic teeth made of ivory (Chandra et al., 2003).
Ivory has a neutral calming colour (HEX #FFFFF0) that has a relaxing effect. The colour is often used for wedding invitations and in other situations that merit a show of elegance: a good example is wedding dresses, particularly for women with a fair skin tone. Ivory coloured leather automobile interiors also represent luxury. In Chinese culture, ivory is though to bring good luck and success to the owner (Christy, 2012) – something that elephants are likely to dispute (Wasser et al., 2010).
Ivory research: in literature and culture
As a material known since ancient times, ivory has acquires cultural significance that mostly revolves around the high status of people possessing it. Ivory colour came to signify beautiful healthy skin, and the term “ivory tower” means a community of academics engaged in deep research that is so fundamental and deep as to have little effect on the outside world (Lovitts, 2001). This latter term is often used pejoratively against top-ranking institutions that are often accused of being detached from reality (Bok and Bok, 2009).
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