AIC's 45th Annual Meeting

New technology can unlock the secret of dyes used in historical artifact and facilitates the formulation of appropriate conservation strategies for preserving cultural heritage. The application of advanced analytical techniques, initially developed in the field of analytical Science, provides conservators a tool to identify composition and to review information of where, when and how the artifact be formed. The result provides insights to conservators to devise a comprehensive treatment proposal. In recent decade, numerous literatures had been reported in the identification of dyes used in historical paintings or textiles with various analytical techniques [5-7]. Yet, the analogous studies of dyes on Chinese documents are less explored [8]. With continuous interest to investigate the dye used in Pearl River Delta region in China [9], herein we describe an investigation of synthetic red dyes used in a set of Chinese wedding documents predates from 1910's to 1950's which are the collection of Hong Kong Museum of History. Marriage is of fundamental significance in the rituals of traditional Chinese culture, which are generally known as the "Three Covenants and Six Rites”[1]. "Three covenants” are the wedding documents exchanged between the two families to confirm the engagement of marriage, which are important records for the Chinese heritage and thus of great historical significance. Most of the documents have suffered from various degrees of paper damages such as tears, lose, distortion and running of the colour. Hence, an effective and safe conservation treatment is of stark importance. Red is an auspicious color which usually corresponds to good fortune and happiness, hence the traditional wedding documents are all made in red [2]. Natural red dyes such as Ocher (mineral dyestuffs), Alizarin (plant dyestuffs) and Carminic acid (animal dyestuffs) were originally used in ancient time [3]. They were the only source of red until synthetic dyes were introduced to China in the late 19th century. Since then, natural dye had been entirely replaced by synthetic dyes due to the wider color ranges, composition uniformity, low costs and stability towards fading [4]. However, most of them are water-sensitive required special attention. To shed light on their histories and associated chemistry of the dyes, samples from the wedding documents taken at ten-year intervals were subject to study by various analytical methods including UV-Vis spectroscopy, TLC and Ultra-performance liquid chromatography with both diode array UV-Vis detector and time-of-flight mass spectrometer (Reverse phase UPLC-DAD-ESI-Q-TOF-MS). In the preliminary investigation, four synthetic dyes (Rodamine B, Rodamine 575, 2-Napthol orange and Aniline yellow) have been identified, indicating that they were already commonly applied during that period of time. Given the identified dyes are all relatively water soluble, conservators should consider alternatives to traditional wet treatment method, such as a dry lining Chinese mounting method for this type of wedding documents. This paper will extensively discuss on the new findings and this special technique in the course of treatment.