Tortoiseshell tests

Sectility. This is not a useftil test as horn, like tortoiseshell and plastic, can be paired with a sharp knife. 

Most tests on tortoiseshell are destructive, so identification is best done by sight. 

Ultraviolet light. The first of the two tests that does not in any way harm the material is to view it under UV light. Both tortoiseshell and horn show a slight fluorescence, especially in the blond areas, whereas plastic - with the exception of casein - is inert. 

Burning and hot-point tests. Tortoiseshell bums at a lower temperature than horn. A sliver of either will bum with the typical small of burning hair because they are basically made of the same material. It is a destmctive test and so it is preferable to cut a minute sliver of the material from an area where it will not be noticed, rather than stick a hot needle into the item. Plastics give off a typical, acrid smell when they bum. 

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. 

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