The historical origins of dragon's blood - the deep red resins obtained from Dracaena plants - can now be used to identify accurately resins of unknown origin, according to scientists at Bradford University.

Howell Edwards and colleagues used Raman spectroscopy to characterise these resins without damaging them. They used the information collected to construct a database to identify the origins of resins. Researchers examined dragon's blood specimens from a vast archive collection at the Royal Botanical Gardens at Kew, and have catalogued the characteristic spectra of these materials.

The resins have been used in artistic and pharmaceutical applications since Roman times, and owe their highly coloured properties to the presence of dracorubin and dracorhodin compounds. Original sources are known to be the dragon tree Dracaena cinnabari found on the island of Socotra, Yemen. However, due to the valuable nature of these substances, substitutes were sought during mediaeval and Renaissance periods. These mainly originated from trees such as Daemonorops and Croton, which have superficial similarities to the Dracaena materials and which originate from the Mediterranean and parts of Asia.

The group's research should be of particular interest to art restorers and conservators who need to identify pigments present in their artefacts in order to find suitable modern replacements in the reconditioning process, and also to archaeologists who are interested in tracing ancient trade routes of these substances.

Future studies intend to expand the database further, says Edwards, because the range of ancient resin colorants is diverse. There is also an interest in studying resins which have been subject to other conditions, such as mixed with other pigments or buried for long periods of time. 

Carolyn Ackers