Consolidation and Dehydration of Waterlogged Archaeological Wood from Site Huaguangjiao No.1

Abstract

The Huaguangjiao I is an ancient Chinese wooden shipwreck from the South Song Dynasty (AD 1127–1279) discovered in the South China Sea in 1996. The first phase of its conservation, desalination and desulfurization, was completed in 2016. In this paper, three archaeological wood samples exhibiting different degrees of deterioration from Huaguangjiao No. 1 were consolidated with PEG-4000 and dehydrated via freeze drying and supercritical CO2 drying methods. The dimensional stability, hygroscopicity, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to evaluate the effects of consolidation and dehydration. The results showed that PEG4000 was an efficient consolidation material that also effectively decreased shrinkage during dehydration. Furthermore, both vacuum-freeze and supercritical CO2 drying were efficient methods for treating waterlogged archaeological wood. After PEG4000 impregnation, the shrinkage percentage of the waterlogged archaeological wood became slightly lower than sound wood. The moisture absorption of the experimental specimens ranged within 3.35%–4.53%, and they comprised 50% sound wood, resulting in a marked improvement in dimensional stability. FTIR spectra indicated that impregnation improved wood dimensional stability by reducing hydrophilic groups. These results show that this method can effectively treat waterlogged wood for preservation purposes.