Ivory

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THIS ENTRY IS A DRAFT

Ivory

Materials and technology

Ivory is used to refer to the tooth or tusk of animals. These teeth or tusks are comprised primarily of a material called dentine which grows on the outside of the tooth. Cells inside the pulp cavity of the tooth, which is a hollow space inside the tooth, forms dentine. Dentine contains both an organic and inorganic component. The organic component is composed of collagen based proteins. The inorganic component is made up of dahllite, a carbonate containing hydroxylapatite (Ca₁₀ (PO₄)₆ (CO)₃∙H₂O) (Espinoza and Mann 1992). Regardless of which animal the tusk or tooth comes from, they are all chemically the same.

"Natives with ivory tusks, Dar Es Salaam, Tanganyika" (photo taken between ca. 1880 and 1923)

Materials

The most common animals used as sources for ivory in art objects are elephants, mammoths, hippos, walrus, sperm whales, and narwhals (Hornbeck 2016). Ivory substitutes have also been used. These include materials such as vegetable ivory, made from the nuts of the Tagua palm tree, and celluloid and plastics beginning in the late 19th century.

• Elephant
• Mammoth
• Hippo
• Walrus
• Sperm Whale
• Narwhal
• Ivory substitutes

• Vegetable ivory
• Celluloid/Plastics

Identification

Ivory can be distinguished from similar looking materials (i.e. bone, shell, ivory substitutes) using various techniques. The animal the ivory came from can also be determined.

Examination using Magnification

The most common method used for the identification of ivory is examining the material using magnification to look for diagnostic characteristics unique to each type of ivory. Though all ivories are the same chemically, they can differ in the way they grow and appear from animal to animal. This examination can also help determine whether ivory substitutes or other materials, which look similar to ivory, have been used.

Elephant

· Schreger Lines: Elephant ivory is characterized by its Schreger lines, which are visible patterns of intersecting arcs seen when viewing the ivory in cross-section. In elephant ivory, the Schreger lines form obtuse angles (greater than 90 degrees). The clarity and visibility of these angles can vary depending on how the ivory was cut and are best observed under magnification.

· Color and Patina: Over time, elephant ivory develops a yellow or brownish patina.

· Surface Texture: Under magnification, the surface of elephant ivory can show minute growth lines and pores scattered throughout its surface.

Mammoth

· Schreger Lines: Mammoth ivory's Schreger lines intersect at acute angles (less than 90 degrees). The visibility and clarity of these lines can vary depending on how the ivory was cut.

· Color and Patina: While mammoth ivory can develop a patina similar to elephant ivory, mammoth ivory often shows signs of mineralization due to being buried for millennia. This can affect its coloration, with some pieces exhibiting blue or green hues under magnification.

· Surface Texture: The texture of mammoth ivory can show more pronounced variations due to its age and the conditions under which it was preserved.

Hippopotamus

· Density and Color: Hippopotamus ivory is denser and often whiter than elephant ivory. Under magnification, it may not show the distinctive Schreger lines but can have a fine, homogeneous grain.

· Cross-section Appearance: The cross-section of hippo ivory lacks the clear Schreger pattern seen in elephant and mammoth ivory. It might show a more uniform texture, with less visible growth lines.

Walrus

· Secondary Dentine: Also known as "marble" or "oosik," the inner part of a walrus tusk shows a unique, mottled texture under magnification, distinct from the layered structure of elephant and mammoth ivory.

· Surface Texture: The surface of walrus ivory may have longitudinal cracks and a less polished appearance than elephant ivory, with growth lines visible under magnification.

Sperm Whale

· Structure and Texture: Sperm whale ivory is known for its dense, fine texture. It shows concentric growth rings under magnification. These rings are not as pronounced as those in narwhal ivory and do not exhibit a spiral pattern.

· Color: Freshly cut sperm whale ivory can be very white, becoming more yellow with age. The patina developed over time is generally lighter and less pronounced than that of elephant ivory.

· Cross-section Appearance: In cross-section, sperm whale ivory is generally uniform with a subtle, waxy luster. The absence of the large pulp cavity seen in elephant and mammoth tusks is notable, as sperm whale teeth are solid ivory throughout.

Narwhal

· Spiral Structure: The surface of a narwhal tusk is smooth, with a ridge that spirals to the left. This external spiral groove corresponds to the internal structure and is a key identifying feature, observable even in worked pieces. This characteristic is unique among ivories and can be seen without magnification, though details are clearer under it.

· Cross-section Appearance: Narwhal ivory does not show Schreger lines but has a concentric ring pattern similar to a tree’s growth rings, visible under magnification.

Vegetable Ivory (Tagua Nut): This plant-based material can mimic ivory but is much smaller in size and has a distinctly different cellular structure under magnification, with no growth lines or Schreger lines.

Bone and Antler: These materials can be distinguished from ivory by the presence of Haversian systems, visible as tiny channels or canals under magnification, which are absent in genuine ivory.

Synthetic Materials: Plastics and other synthetics used as ivory substitutes often have uniform color and lack the natural growth lines and textures of genuine ivory. Under magnification, synthetic materials may show mold lines, air bubbles, or a completely homogenous texture, unlike any natural ivory.

When differentiating ivories, the combination of these features, observed under magnification, provides the necessary clues to accurately identify the material's origin. It's important to note that expertise and experience are crucial for making precise identifications, especially when distinguishing between materials with subtle differences.

Samples of ivory, bone and ivory substitutes under long wave ultraviolet light(365nm). From left to right: mammoth ivory, bone, tagua nut (vegetable ivory), and celluloid.

Examination using ultraviolet (UV) light

Examining an object thought to be ivory using ultraviolet light may help determine whether the material is ivory or made from another material. Using long wave ultraviolet light, materials will fluoresce different colors or absorb the UV light helping to characterize it.

All ivory fluoresces under UV light and appears bluish-white (Hornbeck 2010). Bone and shell have a similar fluorescence to that of ivory. Vegetable ivory will appear slightly orange or warmer in tone. Plastics will absorb UV light and appear dull blue (Espinoza and Mann 1992).

Ivory and Scrimshaw

Was elephant ivory ever used to create scrimshaw? Dr. Stuart M. Frank's reply to Jean Portell's question is a a firm negative. Here, verbatim, is Stuart Frank's emailed response:

"... the answer to your question is resoundingly and unequivocally clear: elephant ivory was never used for scrimshaw. Not even once. If we find any evidence of elephant ivory on something that looks like scrimshaw or is masquerading as scrimshaw, it's a sure-fire indication of fakery. It's one of the first things we look for todetect fraud, and is evidence sufficient in itself. I have testified in Federal court on exactly this point. Pachyderm ivory (including elephant, mammoth, and mastodon) is almost always (99.9% of the time) readily identifiable by Schreger Lines and a distinctive grain that does not appear in any other species. Whalemen had sperm whale skeletal bone and sperm whale teeth aplenty, they were free, and were a trophies of the hunt; and walrus ivory was sometimes acquiredby barter with Eskimos and Inuit, a trade that was also an integral component of the hunt. Elephant ivory, on the other hand, was irrelevant and not obtainable on shipboard; and the places where it could theoretically be acquired were simply not ports-of-call for whalers -- with the exception of Honolulu, where it was very expensive (especially compared with free).The newly formed ASCA (American Scrimshaw Collectors Association) has as part of its mission to make the very distinctive points that: [1] elephant ivory wasnever used for whalemen's scrimshaw, [2] scrimshaw is an indigenous occupational pursuit of whalers and is an indigenously American pursuit, thus part of our national heritage (dating from circa 1766) and a product of the seafaring prowess of the Young Republic, [3] scrimshaw was a grassroots vernacular genre, practiced by blue-collar common seamen and gentleman-officers alike, notably including African Americans, fugitive slaves, Native Americans, immigrants from Europe, Africa, Asia, and South America, as well as mainstream Yankee farm boys (unlike elephant ivory carving, which is foreign, practiced by professional artisans, marketed commercially, and intended as expensive decorations for the privileged), and importantly [4] no whale was ever killed for the ivory — not even one: whale ivory and whale bone were strictlyafter-market byproducts used by the whalemen for their own tool- and souvenir-making. (The economics are simple: in 2015, the meat and bone byproducts of a sperm whale, depending on size, would be worth $6-12 million in Japan; the ±42 teeth of an exceptionally large sperm whale whale with perfect, well formed teeth -- the very highest quality that could be obtained -- might be worth 0.005% of that on a good day; in other words, next to nothing by comparison.) I repeat: while African and Asian elephants are killed and poached for the ivory all the time, no whale was ever killed for the ivory."

Deterioration of Ivory

Both the inorganic and organic components of ivory can be susceptible to damage and deterioration.

• Humidity
• Cracking
• Staining
• Burial Environment

Conservation and care

This information is intended to be used by conservators, museum professionals, and members of the public for educational purposes only. It is not designed to substitute for the consultation of a trained conservator.

• To find a conservator, please visit AIC's Find a Conservator page.
  

References

click on the link to left to download the guide

Espinoza, E. O. and M-J. Mann. 1992. "Identification guide for ivory and ivory substitutes". 2nd ed. Washington D.C.: World Wildlife Fund

Hornbeck, S. 2016. "Ivory: identification and regulation of a precious material". Washington D.C.: Smithsonian National Museum of African Art.

Further reading

"Guidelines for Identifying Ivory." U.S. Fish and Wildlife Service, 2014.

Hornbeck, Stephanie E. "Elephant ivory: An overview of changes to its stringent regulation and considerations for its identification." In Proceedings of the International Conference on the Conservation of Cultural Heritage, edited by J. Doe and A. Smith, 2015, pp. 142-156.

Espinoza, Edgard O., Mary-Jacque Mann. "Identification Guide for Ivory and Ivory Substitutes." CITES, 2012.

Espinoza, Edgard O. and Baker, B. W. and Berry, C. A. 2007. The Analysis of Sea Turtle and Bovid Keratin Artefacts Using Drift Spectroscopy and Discriminant Analysis. Archaeometry. Vol 49(4): 685-698.

Lauffenburger, Julie A. "Baleen in museum collections: Its sources, uses, and identification.” Journal of the American Institute for Conservation. Volume 32, number 3. 1993, pp. 213-230.

R.S. Wilkinson. 1997. Ivory, an historical survey: an annotated bibliography.

Read AIC's Ivory Position Paper on the impact of U.S. government action on cultural property, legislation, and regulations relating to African elephant ivory on AIC's Core Documents webpage

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