Mazarin Chest - further investigation & academic partners

The collaborative cross-cultural approach on which the Mazarin Chest Project is based required that both Japanese and Western conservation techniques were considered. These had never before been compared in a systematic way. The scientific components of the Mazarin Chest Project were intended to support the project team and to allow evidence-based decisions about conservation treatments to be made.

Developing a methodology for artificially ageing lacquer

Investigations into the removal of degraded varnish from, and the treatment of micro-cracks in photo-degraded lacquer required that different possible techniques be tested. As we cannot experiment on the object itself, we aimed to produce artificially aged lacquer samples that simulated the surface of the Mazarin Chest.

A board was prepared in the traditional manner by applying various layers of different types of urushi over foundation layers on a Japanese cypress (hinoki) substrate. Each layer was cured at high relative humidity (approximately 80%) before the next layer was applied.

Further Investigation and Academic Partners

This is a collection of images relating to Further Investigation and Academic Partners

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  Developing a methodology for artificially ageing lacquer, figure 1

  This is an SEM image of the surface of the Mazarin Chest, showing the network of fine cracks on the Chest caused by exposure to light and cycling relative humidity over the past 350 years.

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  Developing a methodology for artificially ageing lacquer, figure 2

  Developing a methodology for artificially ageing lacquer, figure 2

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  Developing a methodology for artificially ageing lacquer, figure 3

  This SEM image shows that no observable change was caused by exposing a sample to light sources that imitated daylight for an extended period.

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  Developing a methodology for artificially ageing lacquer, figure 4

  This SEM image shows the cracks caused by thermal shock, induced by exposing the lacquer sample to liquid nitrogen.

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  Developing a methodology for artificially ageing lacquer, figure 5

  Developing a methodology for artificially ageing lacquer, figure 5

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  Developing a methodology for artificially ageing lacquer, figure 6

  This SEM image shows the damage caused by exposing the sample to a mercury tungsten light source and cycling relative humidity. This is the closest match to the surface of the Mazarin Chest achieved so far, but work is ongoing.

Samples (12 x 12 x 8mm) were cut from this board and then different light sources and humidity/temperature conditions were employed in an effort to simulate the naturally aged surface of the Mazarin Chest. Samples were compared using scanning electron microscopy (SEM).

Researcher: Dr Brenda Keneghan, V&A
Consultant: Dr Cosmas Vlattas, Mechanical Engineer

This research will be published in 2010.

Investigations of physical properties of Japanese cypress (hinoki) and lacquer

The original cleated construction of the lid of the chest, combined with dimensional changes of the wood in response to fluctuations in relative humidity (RH) has caused cracks in the lid and damage and loss to the lacquer (figure 1 above). Whilst losses are most dramatic on the exterior of the lid, it was a smaller crack on the interior that caused most concern, as it had encroached onto an otherwise pristine surface.

We wanted to be able to predict the relative humidity conditions needed for the future in order to prevent propagation of the crack. To do this, it was necessary to establish the amount and way that moisture is absorbed by wood and lacquer (sorption isotherms), the dimensional response (swelling isotherm) of wood and lacquer to fluctuations in relative humidity, and how fast moisture moves through these materials (moisture diffusion coefficients). We also wanted to better understand how the crack affects the moisture distribution in the wood and lacquer as they responded to fluctuations in relative humidity.

The main conclusion of this research was that the dimensional response of the wooden elements restrained by the cleated (hashibami) construction of the chest, as well as of the lacquer layer restrained by the wood support beneath were the principal factors bringing risk of mechanical damage. The lacquer layer, though retarding the water vapour diffusion into the wood, could not mitigate the stress development in the object. Therefore, on physical grounds, the evidence did not support the application of urushi lacquer into structural cracks to prevent uneven uptake of moisture and thereby reduce future damage. The selection of materials for sealing, infilling or retouching should be guided by aesthetic or ethical considerations.

In addition, this research concluded that:

Researchers: Dr Lukasz Bratasz and Dr Roman Kozlowski
Institute of Catalysis and Surface Chemistry
Polish Academy of Sciences

PhD Research

PhD: Conserving Tangible and Intangible Cultural Heritage: Removing Degraded Western Varnish from photo-degraded Japanese Lacquer

When newly manufactured, East Asian lacquer is typically characterised by a glossy lustrous surface. As lacquer ages, its appearance changes and it becomes progressively more dull. Western coatings have been applied to dull lacquer in an attempt to resaturate the colour and restore the original gloss. Unfortunately, they do not replicate the original appearance of lacquer and tend to compromise the subtlety of the decoration. Further, Western varnishes can damage the original lacquer as they age and degrade in turn. The more aged the lacquer surface and the more degraded and oxidised the Western coating, the more difficult it is to remove the varnish without damaging the original lacquer. The problem of removing degraded Western varnishes from East Asian lacquer affects a substantial proportion of such objects held in public collections in the West. This problem has also been encountered in Japan, where some significant Japanese lacquer objects held in Western collections have been sent for conservation. The focus of this PhD was the potential use of solvents to remove degraded varnish from photo-degraded Japanese lacquer.

Research involved the review of the chemistry of this unique material, and the distinction between different East Asian lacquers was 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 recreated artificially. The advantages and limitations of such an approach were 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 were also investigated to determine potential 'safe' solvents for conservation cleaning. These studies showed 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 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.

Chemistry Department, Imperial College (a collaborative IC/V&A doctorate funded by the AHRC)
Student: Carolyn McSharry
Supervisors:
Professor Tom Welton
Dr Milo Shaffer
Dr Rupert Faulkner, V&A
Advisor: Shayne Rivers, V&A
This collaborative PhD is funded by theArts and Humanities Research Council

A literature review of the scientific literature on the chemistry of East Asian lacquer was published in 2007. An additional paper on the solubility parameters of East Asian lacquer will be published in 2010.

PhD: Understanding the behaviour of urushi lacquers using optical and numerical techniques

This PhD programme has been focussed on developing methods for understanding and describing the behaviour of urushi lacquers. We have taken an approach whereby we have identified characteristic behaviour of thin layers of lacquers in conditions that bear similarity to those lacquers are exposed to on the Mazarin Chest. Optical interferometry has shown that the timescales associated with moisture ingress and with relaxation are similar, leading to complex stress responses when the relative humidity of the environment changes.

A simple 1-dimensional model has been developed that captures the response. This model effectively considers the effects of moisture ingress as a two-step process. First the moisture propagates into the material, which can be described with a solution of the diffusion equation. Secondly, the moisture gives rise to a change in dimension, which because of the constraints of the substrate, results in stresses developing. These stresses then evolve as the moisture distribution changes and the material relaxes.

This simple model is attractive since it does not require significant computational power, nor does it require us to measure all of the material properties. However, in order to be able to describe the complex response of a multi-layered urushi coating on a material such as wood, a more complex model is required. We have determined the material properties of urushi as a function of aging and moisture content and the appropriate constitutive model and developed an FE model that will describe the evolving moisture, strain and stress distributions. Validation is ongoing.

Student: Adel Elmahdy
Supervisors:
Dr Ricky Wildman
Dr Pablo Daniel Ruiz
Advisors: Dr Brenda Keneghan and Shayne Rivers, V&A

PhD: The Consolidation of East Asian Export Lacquer Coatings

East Asian export lacquer coatings have a reputation for degrading more easily than those of high quality lacquerware, often developing extensive cracking, delamination and flaking when exposed to fluctuating environmental conditions. This research project aims to systematically approach problems encountered by conservators in their working practice when consolidating such severely degraded coating structures.

A small survey of the V&A's lacquer collection was undertaken to characterise the distinctive types of deterioration and failure of the multilayered Japanese and Chinese export lacquer structures. The composite materials were analysed and the precise location of their failure identified giving clear indication of the causes for coating delamination and flaking. Based on these results, conservation materials used for consolidation (i.e. collagen glues, PVAs, acrylics, traditional Japanese consolidation materials) are reviewed with respect to their efficiency as consolidants for export lacquer foundation layers.

The fracture characteristics of individual layers before and after consolidation are investigated by adapting a recognised test method for determining the fracture resistance of structural adhesive joints. This gives a much better understanding of the behaviour of stressed multilayered coating structures than conventional tensile and shear tests. It promises to be a useful means for analysing the changing toughness characteristics of coating layers consolidated with various adhesives.

A literature review of animal-based glues and their properties in use in conservation was published in 2007 and a paper examining the failure mechanisms in delaminating and flaking East Asian Export lacquer will be published in 2010 .

Student: Nanke Schellmann
Supervisor:Professor Christoph Herm , Dresden Academy of Fine Arts, Germany
Advisors:Dr Ambrose Taylor , Imperial College, London and Shayne Rivers, V&A

PhD: Conservation of Degraded East Asian Lacquer Surfaces (provisional title)

The research is investigating the conditions that initiate and propagate micro-cracking in East Asian lacquer surfaces. The effects that current conservation treatments have on the micro-cracking, and how these treatments behave in the long term will also be considered. The micro-cracking that appears on the surface is thought to be produced by fluctuations in temperature and relative humidity, and is assisted by light degradation. Samples of plain and maki-e lacquer boards with the full layer structure will be artificially aged to replicate the micro-cracking damage seen on naturally aged samples. Various conservation treatments will be applied to these artificially aged samples to investigate the effect that they have on the appearance of the micro-cracking and the strength of the conserved surface. The boards will undergo further artificial ageing to investigate how the treatments affect the micro-cracking in the long term.

The thesis also has a humanities component, which will research the sources of tension when working with cross-cultural objects. Conservation of an historic object can include scientists, curators, conservators and ethnic communities, which can lead to a conflict of ideas and interests. These conflicts have different origins; some are based on cultural differences, historical and traditional values, or miscommunication between differing viewpoints. This project will explore why these tensions arise and in what form they manifest themselves through three case studies. It will explore the role of science in art and how cultural differences can change the way we view an object.

Mechanical Engineering Department, Imperial College London (a collaborative IC/V&A doctorate funded by the AHRC)
Student: Judith Thei
Supervisors:Dr Ambrose Taylor (Imperial College)
Glenn Adamson (V&A)
Advisor: Shayne Rivers (V&A)
This collaborative PhD is funded by the Arts and Humanities Research Council

Modelling Environmental Ageing Behaviours of East Asian Lacquer (Urushi)

This is a joint experimental and modelling project to develop a Finite element method for multi-physical simulation of environmental aging behaviour of East Asian lacquer (urushi). Mechanical testing procedures are used to characterise material response to changes in humidity. In addition, urushi lacquer is artificially aged to address the effect of aging on material properties. Constitutive behaviour of thin lacquer layers is investigated experimentally for construction of a finite element model of urushi thin layer behaviour under a range of conditions. This model includes hygro-UV effects to simulate environmental changes, is time dependent and allows us to predict the stresses and strains that develop as the lacquer is subjected to conditions similar to those experienced when exposed to a standard display environment. The predictions of material behaviour from the finite element method will provides conservators and lacquer researchers with a reference of aging behaviour of urushi lacquerware to make well-informed decisions about conservation treatment.

Student: Xinyi Liu
Supervisors:
Dr Ricky Wildman
Dr Ian Ashcroft
Advisors: Dr Brenda Keneghan and Shayne Rivers, V&A