John Burbidge - 14th July 2003
1. INTRODUCTION
This has been quite a busy month, and by its finish one can see the unifying
effect that the stage II cleaning has achieved. Samples have been collected
from the residue megilp for analysis - the results will hopefully inform the
decision regarding the question of whether or not to apply a protective coating
over the painting once treatment has been completed. A start has also been made
on the assessment and proposals for Phase II of the treatment (retouching and
varnishing) with a view to obtaining a faculty for this work in line with the
architect's revised schedule. Dr. Nicholas Eastaugh in collaboration with his
colleague, Dr Tracy Chaplin have investigated and produced an alternative gel
formulation for the removal of the soffit overpaint. Initial tests prove promising.
2. TREATMENT
2.1 Wall painting
The Stage II cleaning has proceeded as specified in our previous reports. Almost
all of the main and secondary figures have been treated, including areas of
the background. The painting is looking stunning!
Despite the previous stabilisation of all lifting paint with fish glue, an acrylic dispersion and lime slurry where appropriate, widespread lifting of small localised areas of paint has been noticed. Some of this may be a latent effect of the Stage II cleaning process but may also be due to variations in the environment which are probably being exaggerated by our presence. A second phase of stabilisation has begun using an acrylic dispersion (Plextol B500 + deionised water 1:1 v/v) and where necessary a thin lime grout (Totternhoe lime + deionised water).
2.2 Soffit
Following initial research and tests into an alternative solvent gel (to a dichloromethane
gel which could affect the copper green pigment on the soffit), a test sample
has been produced by Dr. Nicholas Eastaugh in collaboration with his colleague,
Dr Tracy Chaplin. The active solvents in the new gel are dibasic ester (50%)
and N-methyl-2-pyrrolidone (41%). Initial laboratory tests were undertaken to
establish the compatibility of the gel with the range of pigments found in the
wall painting which are also likely to be found on the soffit. Small practical
tests have been undertaken on the soffit in order to establish the method of
application. Despite the fact that the complete swelling of the overpaint is
taking more than seven hours, the initial results look promising. As a result
of these initial tests a thicker gel has been formulated.
3. SCIENTIFIC SUPPORT
An alternative gel has been formulated and initial trials are promising (see
above).
The database has had its regular upgrade. Many of the early cross section images, taken by slide then digitised during the initial cleaning tests in the first quarter of 2000, are being re-photographed with a digital camera. This makes them of a comparable quality to the cross sectional images taken since the beginning of the cleaning which were taken with a digital camera. The quality of these images combined with a magnifying tool option is allowing better on site understanding, correlation and interpretation of the samples, maximising their usage and potentially reducing the need for further sampling.
Samples of residue megilp were collected in order to better understand its properties after the cleaning process. This was considered a worthwhile option because of concern about residue megilp picking-up dirt which could eventually become embedded in its surface. Also, there will remain an amount of megilp integrated within the paint structure which has been impossible to remove and could have implications with regard to the future stability of areas of the painting.
Three types of sample were collected:
1. The complete layer: sample 1
2. Discontinuous islands of opaque dark brown residue (cross-linked mastic resin
+ oil), after the bulk of the megilp layer was removed during Stage I cleaning.
Collected from three locations: samples 2a, 2b, 2c
3. Residue film of megilp, after the bulk of the layer was removed during Stage
I cleaning. Collected from three locations: samples 3a, 3b, 3c.
SAMPLE # GRID REF.* DESCRIPTION OF UNDERLYING PAINT LAYER METHOD OF COLLECTION
SOLVENT
1 A9 Green background, some red flowers Cotton wool swabs (1-6) IMS
2a D12-13 Cream coloured shawl from soul rising from tomb PEL tissue (x3) +
scalpel IMS + benzyl alcohol (9:1v/v)
2b M6 Crimson and cream coloured knee of Christ PEL tissue (x3) + scalpel IMS
+ benzyl alcohol (9:1v/v)
2c R11 Pale grey/pink flesh area, leg of "ale wife" PEL tissue (x3)
+ scalpel IMS + benzyl alcohol (9:1v/v)
3a B12 Green background near to #2a Cotton wool swabs(1-6) IMS
3b M7 Green background + red flowers adjacent to #2b Cotton wool swabs (1-4)
IMS
3c U10 Green background + red flowers near to #2c Cotton wool swabs (1-4) IMS
Samples of the materials used in the cleaning procedure (fish glue, acrylic
dispersion, etc.) were sent in order that their values may be removed from the
analysis.
The samples were sent for analysis to Dr Ian Hamerton at the University of Surrey
4. WHAT IS PLANNED AFTER THE CLEANING IS COMPLETED
Phase I of the treatment which comprises of cleaning (the reduction of the megilp
varnish), stabilization of the paint and plaster and removal of the overpaint
to the soffit, is now drawing to an end. It is therefore timely to consider
the next stage of the treatment. After the completion of Phase I, the upper
levels of the scaffold will be dismantled to allow the entire painting to be
viewed from the ground - the first time that the painting will be visible from
the ground for at least 120 years! This exercise will have a twofold purpose:
firstly to assess the needs for display lighting, and secondly to assess the
needs for integration. Working from the ethical basis of undertaking minimal
integration, viewing from the ground (50-70 feet from the face of the painting)
is considered a practical way to judge the overall legibility of the painting
and the absolute minimum that requires integration. There may also be other
issues, such as the irregular surface reflectance caused by the reduction of
the megilp, which may not become apparent until the scaffolding is dropped.
All these issues could also be exacerbated by the proposed artificial lighting
scheme. Once decisions have been made about these, the scaffold will be re-erected
for the completion of Phase II of the treatment.
The method statement for Phase II provided for the integration of losses and the application of a protective coating. Decisions regarding these points are not necessarily straight forward and a number of different aspects need to be considered to ensure an appropriate response. Completion of the assessment and proposals are nearly complete in readiness for submission.
In preparation for the completion of the treatment of the painting, lighting specialist Jim Patterson has visited the site. Initial small trials, including at night time, were undertaken using LED and fibre optic lighting. From these strips of fibre-optics gave a more general "wash" of light to the painting with the possibility of focusing light in specific areas without unduly highlighting disturbing features and causing a great deal of reflectance. A large scale test (north side of the painting) is planned for when the scaffolding is partially dismantled.
The Media Studies Department of Coventry Technical College are willing to produce a CD-ROM and design and host a web site dedicated to the wall painting as a student project. The preparation of a mock-up CD should be completed by the end of July. It is then expected that the photography for the finalised version will take place during the period when the scaffolding is partially dismantled.
5. PRIMARY OBSERVATIONS
With the painting in the final stages of cleaning we are in a better position
to understand the original technique. However, the interpretation of what is
now visible is not always conclusive. For example, while there are numerous
indications of "pentimenti" where the positions of figures have been
changed or in one case completely painted-out (a figure amongst the group of
souls in standing in judgement by Christ's left foot). There are also three
areas which have been repainted in different colours (the rear panel at the
gate to heaven, the tunic of the apostle immediately to the left of Christ and
the tunic of St. Peter). The rear panel at the gates of heaven appears to have
been repainted by Gee, but the tunics of both Apostles appear to be "pentimenti".
We have a fairly clear understanding of the characteristics of the early 19th
century intervention by Gee (calligraphic quality of black lines, fine regular
particles in paint layers and glazes). There are also a number of anomalies
that could indicate an early repainting/restoration of the wall painting (paint
layers that pass over losses in preparation, cannel black used locally to outline
elements of the design and found beneath Gee's work. There is also possible
evidence of different hands at work. At the moment despite numerous paint samples
that have been analysed there is no conclusive proof of repainting. In fact,
the use of cannel black could indicate a change of materials at the time of
the execution of the painting. It is hoped that a final selective sampling will
be able to provide some conclusive evidence.
6. PLANS FOR JUNE
By the end of the month it is hoped that the Stage II cleaning will be complete
and that the soffit will be further advanced. There are plans for a general
meeting with representatives of E.H, C.C.C, etc., to discuss the proposed heating
(a criteria for the Faculty to carry out the treatment of the wall painting),
re-ordering and the implications of this for the wall painting.
Granville & Burbidge, 111
Kingsmead Road, London, SW2 3HZ, Tel/Fax 020 8674 1969
Jenny Granville Dip.Restoration (City & Guilds of London Art School), John
Burbidge Dip.Restoration (Opificio della Pietre Dure, Florence)