Ivory imitations

In 1844, Franc in formed a series of casts in plaster composition, in imitation of ivory and, in 1846, the Society of Arts in London awarded to him a prize. 

John Hyatt was trying to make imitation ivory billiard balls from nitrocellulose and camphor. Instead of ivory , he got a new substance. He called it celluloid . Celluloid has serious disadvantages it is brittle, inflammable and discolours with age. 

Figure 27 Synthetic plastics imitated successfully exclusive natural materials a Bakelite ash tray with built-in match holder and striker in marble Roanoid, with marbleized, brass-tipped cigarette holder, 1930s. Carvacraft desk set in amber cast phenolic, 1948-51 double inkwell, notepad holder, blotter and paper knife with clear acrylic blade. Smiths Sectric alarm clock with marbleized urea-formaldehyde case, 1932. Ardath Tobacco cigarette box in ivory and black urea-formaldehyde with lid moulded to simulate a classical relief, 1935. Propelling pencil with black and orange mottle typical of vulcanite, 1930s (Photo Stephen Brayne, Collection Sylvia Katz)...

The quest for imitations of ivory have led to the use of vegetable ivory, the hard white nuts produced by various tropical trees. The most common of these are the doum palm (Hyphanae thebaica) and the tagua Phytelephas macro-carpa). These nuts have a brown fibrous rind, but the meat inside is homogeneous white or yellowish white. Softer than ivory, these nuts are easy to carve, and are popular for making small items such as netsuke, buttons, beads, and jewelry. 

Resin compositions were also used to make molded decorative and household objects. These compounds were used for the covers of books, picture frames, buttons, and lots of other small objects. Most of these items were black, but sometimes they were made white, as an imitation of ivory. These items are britde and flammable and were the precursors to modern plastics. 

Celluloid, which was patented in the USA in 1870, is a combination of pyroxylin, camphor, and cellulose fiber. It could be molded under pressure, and could be made in any color. Later experiments revealed that certain additives increased its flexibility and luster. Most early celluloid was used to make small household and decorative objects, often in a white or cream color to imitate ivory. With the invention of motion pictures, celluloid became commonly used as film. 

Small pieces of bone have been used to make jewelry, buttons, and other personal items, often in imitation of ivory. Domestic animals that are used as food or beasts of burden are the source of most commercial bone. These include cattle, camel, and water buffalo. Scrimshaw is an art form in which designs are scratched a light-colored material, and then ink or paint is rubbed into the lines. The raw material used is often ivory (teeth) or bone. 

Casein is an insoluble protein found in milk. It is used to make adhesives and fillers, water-resistant coatings, and as an additive in some plastics and commercial food products like non-dairy creamers and soy cheese. The milk from cows, sheep, and goats has been used, alone or mixed with fillers, as gesso or as a tempera medium. Casein mixed with fillers such as sawdust or plant materials has been molded into various objects, such as buttons, knitting needles, button hooks, and jewelry. It has been used as an imitation of ivory under the commercial names erinoid and galalith. 

There exists a wealth of old, jet simulants. Several materials used to make jewellery were black, and further, almost anything could be dyed black. It was much harder to produce plastics in pale colours, or to bleach materials, to imitate a material such as ivory. There are also other coals which were worked in their own right and not necessarily intended as a simulant of jet, but which may be confused with jet. 

Figure 3.9 Ivotine plastic handles, imitating elephant ivory.

Figure 3.11 Moulded plastic imitating ivory carving.

Imitation scrimshaw is made of plastic - for example, epoxy -which is moulded in a silicone rubber mould that is flexible. This enables it to be pealed off the moulded object, and eliminates the risk of marks from joins in the mould. The plastic is weighted to simulate ivory (Figs 3.10 and 3.11). 

Bone is a relatively ineaqtensive material and is fteely available, so it has not been necessary to imitate it. However, bone has itself been used ftequendy to imitate ivory. It also bears some resemblance to antler. 

Reconstituted bone. This material is not common but does occasionally appear on the market in the atm of small ures or netsuke-like carvings . Probably intended to imitate ivory rather than bone, it shows a total lack of structure or marks om carving tools, but will probably show signs of having been moulded. It is made of powdered bone mixed with a filler. 

Injection moulding is used in the production of inexpensive jewellery in such forms as beads or bangles with patterned surfaces, and items such as brooches and cameos that imitate coral or shell. Other examples of products made this way are the ivory carvings which are often slightly flexible (Fig. 3.11). 

Casein was versatile in that it could take any colour, or could be moulded in a combination of colours, which made it a very attractive plastic. Its most common uses were as knitting needles and fountain pen barrels. The latter often displayed a pearly lustre. Casein is still in use today for button manufacture. It was also made into brightly coloured jewellery, such as linked bangles. It made a good imitation for ivory as it has a very similar fluorescence under ultraviolet light - the only plastic to display this. 

A Turkish sabre of ancient manufacture from Constantinople is shown in Fig. 3. The handle is painted a dull creamy white in imitation of ivory. The enamel paint sold in small tins will answer well for this purpose. The cross guard and blade are covered as described in Fig. 1. The sharp edge is on the longer curved side, the other is flat or half-round. 

The first man-made polymer was nitrocellulose (NC). The main use of the NC resins was a replacement of the natural and expensive materials, viz., ivory, tortoise shell products, amber, ebony, onyx or alabaster. The use of cellulose acetate (CA) as a thermoplastic began in 1926. Cellulose ethers and esters became commercially available in 1927. Casein crosslinked by formaldehyde gave horn-like materials — Galalith has been used to manufacture shirt buttons, or as imitation of ivory and porcelain [Pontio, 1919]. 

Ivory consists mainly of inorganic material, primarily calcium phosphate, which makes it non-flammable and non-melting. These properties distinguish it from the kind of polyamides occasionally used for imitation ivory (polyamides see also Section 6.2.10). 

While vulcanization of NR and GP was the first purposeful modification of natural polymers, the first man-made polymer was nitrocellulose, NC, discovered by Braconnot in 1833 (see Appendix I). Several commercial products followed, e.g., Collodion (lacquers based on alcohol-ether solution), Parkesine (the first thermoplastic material hot rolled and formable into variety of shapes), Ivorite (used as a substitute for ivory). Celluloid (camphor plasticized NC). Cellulose acetate, CA, was introduced in 1869 by Schutzenberger. Casein crosslinking by formaldehyde resulted in a 1885-patent hy Kritsche and Spitteler for what later became known as Galalith, a horn-like material quite successfully used even today as an imitation of ivory and porcelain [Seymour, 1982 1989]. 

Figure 15 FT-Raman spectra of fake ivory specimens (a) carved X ctorian bangle, (b) large bangle, (c) small bangle, (d) cal. The absence of the characteristic proteinaceous features in true ivory near 1650 and 1450 cm and the strong phosphate mode near 960 cm" should be noted. Also, the presence of the aromatic ring bands at 3060, 1600, and 1000 cm" in (b) and (d) indicate a polystyrene resin content, whereas the carbonyl stretching band at 1725 cm" in all fake specimens indicates the presence of poly(methyl methacrylate). In the cat specimen, the band at 1086 cm uniquely identifies a calcite additive in the specimens of imitation ivory studied. (Reproduced with permission from HGM Edwards, DW Farwell. Ivory and simulated ivory artifacts Fourier-transform Raman diagnostic study. Spectrochimica Acta, Part A, 51 2073-2081. 1995, Elsevier Science B.V.)...

Raman spectra of (A) African elephant ivory, (B) micarta, (C) an imitation ivory and (D) calcite. 

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