Cellulose tortoiseshell

Note A further reason for burning only a small sliver of the material is that the most common early plastic used as an imitation of tortoiseshell was celluloid (cellulose nitrate), a very highly inflammable product. This material catches light with an explosion and immense care must be taken if there is any possibility whatsoever that the item to be tested could be made of celluloid. Also, some plastics melt quickly so a hot needle can cause a lot of damage to an object. 

Celluloid—a very useful substitute for horn, tortoiseshell, ivory, c.—was first made in 1869 by treating nitrocellulose with camphor and alcohol. Its inflammability, however, has proved to be a very serious drawback, attempts to overcome which have met with some success, By the substitution of acetate of cellulose for cellulose itself in the process, a non-inflammable product—sicoid or cellon—is formed which for some purposes is more useful than celluloid. 

Semi-synthetics Cellulose nitrate Synthetic ivory, tortoiseshell, film base Rayon, Celanese, Tricel... 

Cellulose nitrate was originally developed to imitate expensive natural materials such as tortoiseshell. Decorative hair combs made from celluloid in the 1920s look similar to genuine tortoiseshell. 

It is easier to characterize unknown material if its historical and technological backgrounds are known. The development of semi-synthetic polymers in the second half of the nineteenth century can be followed using patents (Fernandez-Villa and Moya, 2005). Development of cellulose nitrate was prompted by the need to find substitutes for natural materials including tortoiseshell, ivory and ebony, which were very expensive. By 1858, approximately 8 per cent of British patents concerned the synthesis or moulding of semi-synthetics. 

A century ago, the polymer industry was in its infancy. The first man-made plastic, a form of cellulose nitrate, was exhibited at the Great International Exhibition in London in 1862. The exhibits were arranged into 36 classes. Amongst the 14000 exhibits of Section C of Class 4 (animal and vegetable substances used in manufecture) was a set of small mouldings made Ity Alexander Parkes fi om a material he named Parkesine. It was described in the exhibition leaflet as a replacement for natural materials such as ivory and tortoiseshell which were becoming rare and nqjensive. 

One interesting thermoplastic material where swirls are often desirable is cellulose acetate. This is an interesting polymer that is made from cellulose— plant fiber. While it is used for photographic film, a more interesting use as it relates to feel is in eyeglass frames and women s hair care products—combs, brushes, barrettes, etc. Cellulose acetate has a slight amount of transparency, as well as a certain amount of iridescence. In the hands of a skilled craftsman, parts made from cellulose acetate can mimic the look of tortoiseshell and ivory and even sea shells such as abalone (Figure 7.12). 

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