Conserving tangible and intangible cultural heritage: cleaning degraded East Asian lacquer
Author(s)
McSharry, Carolyn Heather
Type
Thesis
Abstract
East Asian lacquer (urushi) is a natural, thermosetting polymer, characterised by its
durability and gloss. Prolonged exposure to light, however, causes photodegradation,
which initiates microcracking in the surface layers. Accumulation of dirt, grease, or
non-original materials, such as varnishes applied during attempted restoration,
contributes to deterioration of the lacquer’s appearance through discolouration. This
build up must be removed in order to conserve affected pieces, and the potential use
of solvents to achieve this aim is investigated here.
This work presents a review of the chemistry of this unique material, and the
distinction between different East Asian lacquers is investigated. Valuable, rare
lacquer samples could not be taken from naturally aged museum pieces in order to
investigate the applicability of solvents in cleaning conservation processes, and so the
damage featured on the models used was recreated artificially. The advantages and
limitations of such an approach are assessed in terms of the practical value of the
resulting samples as credible models compared to the naturally aged material.
In free film studies, solubility parameters were determined for a range of lacquers,
and the morphological changes that result from solvent exposure are also investigated
to determine potential ‘safe’ solvents for conservation cleaning. These studies show
that most solvents are damaging to photodegraded lacquers to some extent, and the
possible risks must be assessed against the need for removal of a damaging layer. The
findings reported here have implications for the choice of solvents used in
conservation cleaning, but other solvent properties and behaviours must be considered
along with these data when identifying the least damaging, yet effective solvents.
durability and gloss. Prolonged exposure to light, however, causes photodegradation,
which initiates microcracking in the surface layers. Accumulation of dirt, grease, or
non-original materials, such as varnishes applied during attempted restoration,
contributes to deterioration of the lacquer’s appearance through discolouration. This
build up must be removed in order to conserve affected pieces, and the potential use
of solvents to achieve this aim is investigated here.
This work presents a review of the chemistry of this unique material, and the
distinction between different East Asian lacquers is investigated. Valuable, rare
lacquer samples could not be taken from naturally aged museum pieces in order to
investigate the applicability of solvents in cleaning conservation processes, and so the
damage featured on the models used was recreated artificially. The advantages and
limitations of such an approach are assessed in terms of the practical value of the
resulting samples as credible models compared to the naturally aged material.
In free film studies, solubility parameters were determined for a range of lacquers,
and the morphological changes that result from solvent exposure are also investigated
to determine potential ‘safe’ solvents for conservation cleaning. These studies show
that most solvents are damaging to photodegraded lacquers to some extent, and the
possible risks must be assessed against the need for removal of a damaging layer. The
findings reported here have implications for the choice of solvents used in
conservation cleaning, but other solvent properties and behaviours must be considered
along with these data when identifying the least damaging, yet effective solvents.
Date Issued
2009-06
Date Awarded
2010-02
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Faulkner, Rupert
Shaffer, Milo
Rivers, Shayne
Sponsor
Arts and Humanities Research Council
Creator
McSharry, Carolyn Heather
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)