New Insights into the Cleaning of Paintings

Extended Abstract—The Effect of Conductivity
on Water Solubility: Cleaning a Modern
Chinese Oil Painting
Gillian Osmond and Anne Carter
INTRODUCTION
In preparation for the 2009 exhibition The China Project (Queensland Art Gallery,
Brisbane, Australia), Wang Youshen’s 1986 painting Yu Gong and His Later Generations
was cleaned. Wang graduated in 1988 from the Folk Art Department of the Central
Academy of Fine Arts, Beijing, majoring in illustration and graphic art. Wang’s practice
was formed during the New Wave period (1985–1989) in China, and he was included in
the seminal 1989 exhibition China/Avant-garde held in Beijing.
The Queensland Art Gallery’s painting is a rare early student work on hardboard. It
is unvarnished, well bound, and of variable gloss (Figure 1, left). The paint film is generally
stable; however, there are areas of yellow paint that are actively flaking. The painting
was very dirty. Solubility testing showed that dirt was best removed using aqueous solutions
but that all colors were sensitive in deionized water, particularly red paint.
MATERIALS AND ANALYSIS
Gillian Osmond, Centre for Contemporary Art
Conservation, Queensland Art Gallery | Gallery
of Modern Art, P.O. Box 3686, South Brisbane,
Queensland 4101, Australia, and Australian Institute
for Bioengineering and Nanotechnology,
University of Queensland, St Lucia, Queensland
4072, Australia. Anne Carter, Centre for Contemporary
Art Conservation, Queensland Art
Gallery | Gallery of Modern Art, P.O. Box 3686,
South Brisbane Queensland 4101, Australia. Correspondence:
Gillian Osmond, gillian.osmond@
qagoma.qld.gov.au; Anne Carter, anne.carter@
qagoma.qld.gov.au. Manuscript received 19 November
2010; accepted 24 August 2012.
The artist recalled using oil paint made locally in China (Tianjin) in the 1980s but
could not remember the brand name. He did not use varnish but described mixing locally
manufactured “megilp” with the oil paint (Summer Sun, ShanghART, and Wang Youshen,
personal communication, 11 March 2010). Ultraviolet fluorescence imaging shows variable
fluorescence, with pentimenti also visible as fluorescent underlayers (Figure 1, right).
Analysis using in situ X-ray fluorescence spectroscopy, scanning electron microscopy
coupled with energy dispersive X-ray spectroscopy of embedded cross sections, and Fourier
transform infrared spectroscopy (FTIR) of paint samples revealed that zinc is widely
present, predominantly as zinc stearate. Most paint layers contain similar inorganic material,
including barium sulfate, silicates (kaolin and silica), chalk, and other earth elements.
There are two distinct reds visible in cross section; they have different ultraviolet
fluorescence properties and are distinguishable with backscatter electron imaging by the
varying concentration of barium sulfate present. The FTIR analysis of two samples of red
paint detected the presence of organic pigment PR3 (toluidine red) along with mixtures
of drying oil and natural resin. The red sample with more barium sulfate also possibly
contains wax but not zinc stearate.