In situ chemical analysis of tattooing inks and pigments: modern organic and traditional pigments in ancient mummified remains

At various points in human history, tattooing has been ubiquitous on almost every continent on Earth, used for reasons of aestheticism, religious beliefs or for social purposes. To study the art of tattooing with respect to a particular culture, one must always be critical to any references to the practice (written, pictorial or artefactual) due to issues of translation and misinterpretation. Complete verification may only come with the discovery of actual tattooed human remains. In combination with artefactual and anthropological evidence, these remains not only provide physical proof of the practice in a culture's ancestry but also possess the ability to link various other forms of physical evidence, which on their own would remain speculative. By its very nature, tattooing may only exist while the bearer is alive. Once the owner dies, the skin, along with the tattoo, decomposes (under normal decomposition conditions) and is lost forever. However, tattoos may survive if the dermal layers of the skin are preserved, either by natural or artificial means. The processes of mummification in various civilisations have provided us with a rare opportunity to study the art and processes of tattooing in antiquity. Existing tattooed mummified remains have been found in: Egypt; Siberia; Eastern Central Asia; Greenland; Alaska and St. Lawrence Islands; Central Andes (Peru and Chile); Philippines; New Zealand and Italy. Existing literature regarding the analysis of tattooing inks and pigments once deposited into the skin is very limited. Comparatively, the industrial organic pigments used to colour the majority of modern tattooing inks sold today have not been officially approved by any regulating body and as such, manufacturers are not required to disclose the chemical ingredients of their products. Chemical identification of these tattoo pigments post-procedure will aid medical practitioners in the event of complications or for the purposes of tattoo removal. Forensically, tattoos are often one of the distinguishing features used in the identification of victims of crime or accidents. Experiments were carried out using an animal model (Sus scrofa) for the tattooing. Given the theoretically large but ultimately limited range of substances available to both ancient and modern tattooists, the premise of the experiment involved surveying the literature regarding possible tattooing pigments and either obtaining or reproducing a careful selection of these in the laboratory. These pigments were then tattooed onto the ii animal model and after allowing for the essential healing period, the tattooed areas were excised, with those tattooed with traditional pigments subjected to various simulated mummification environments.