Examinations of East Asian Lacquer

Qi lacquer (also called East Asian lacquer or urushi), is obtained from the lacquer tree. It has been known in East Asia since the Stone Age and is still used today as a decorative and protective coating of small articles of daily use. The labor-intensive harvest and processing produces a shiny, black, polymeric substance as a yield.

On the terracotta figures from the burial complex of Qin Shihuang, qi lacquer was used as a ground layer. Although qi lacquer layers are extremely durable and can survive thousands of years, the lacquer layers on the terracotta figures and on many Han dynasty objects from the region of Xi’an show distinctive serious damages. During the 1990’s, extensive research focused on the identification of the structure and composition and on the stability of the aged and humid lacquer layers, especially their reactions to fluctuations of the humidity. The lacquer was applied in two layers, and it may have contained organic additives which could not be identified anymore. The lacquer layers have micropores with a diameter of only a few 100 nm, they are not translucent and waterlogged from the long period of being imbedded in humid soil. A decrease of the relative humidity below 92 % results in warping of the lacquer. Before larger cracks and detachments of the lacquer layers become visible, microcracks occur and the inner structure collapses – an irreversible damage.

The investigations were carried out in co-operation with the Central Laboratory of the Bavarian State Department for the Preservation of Historic Monuments, Dr. Herbert Juling at the Bremen Institute for Materials Testing (MPA) and the team of Dr. Gerd Guelker, Institute for Physics, Study Group ‘Applied Optics’ at the Carl-von-Ossietzky-University Oldenburg. The results of the researches were the base for the development of suited conservation methods.

Dr. Cristina Thieme (1991-1996)

Prof. Dr. Christoph Herm (1993-1996)

Dr. Catharina Blaensdorf (1998-2000)