Identification of the proto-inkstone by organic residue analysis: a case study from the Changle Cemetery in China

The inkstone is a specific writing implement in China that was popularized since the Han Dynasty (202 BC–AD 220). A rectangular/round grinding plate accompanied with a grinding stone is considered as a kind of proto-inkstone. However, little scientific investigation has been performed to support this hypothesis. In this paper, a micro-destructive approach, including Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and gas chromatography coupled with mass spectrometry (GC–MS), were employed to analyse the black residues on a grinding plate and a grinding stone excavated from the Changle Cemetery (202 BC–AD 8) in northwestern China. The FTIR and Raman analyses indicated that the residues were ancient ink. GC–MS analysis further identified that the residues were pinesoot ink, based on the relative abundances of the main polycyclic aromatic hydrocarbons, as well as the detection of conifer biomarkers. The trace of animal glue was not detected in the residues; thus, the ink was possibly formed as small pellets and the small grinding stone was necessary to assist during the ink-grinding process. This study confirms that this set of stone implements is indeed an early type of inkstone, and offers some insight into the co-evolution relationship between ink production and inkstone shapes.