A view of the beautiful hand carved Victorian pews with "Polly" the Eagle Lecturn.  The lecturn masqueraded as a money box during 1649 - 1660.

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GRANVILLE & BURBIDGE
CONSERVATION AND RESTORATION
HOLY TRINITY CHURCH, COVENTRY

THE CONSERVATION OF THE "DOOM" WALL PAINTING
INTERIM REPORT (OCTOBER 2002)

 

  1. Introduction.

  2. Documentation

  3. Treatment 

  4. Scientific Report

  5. Environmental Monitoring

  6. Primary Observations

  7. Plans for November

1.INTRODUCTION

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October was a busy month and the treatment has proceeded well, despite a number of changes in the team.  Lucy Bunning has left to take up full time employment, and both Victor Hugo López Borges and Rachel Witt have left to work on other projects.  In compensation we have been joined by Adam Webster who is working alternating weeks with English Heritage in their easel painting studios.

We are making good headway with the cleaning and stabilization of the painting.  Further samples have been taken to answer specific questions about the paint structure and previous interventions, and the first phase of environmental monitoring equipment has been installed.

2.DOCUMENTATION

2.1     Photography
Martyn Bowen has completed the photographic survey in u.v and tungsten light before treatment.  Also, three specific areas were retaken with i.r, u.v. and tungsten.  It is planned to repeat this series of photographs during and after cleaning to provide a comparable pictorial record of the treatment.  The painting is not an easy object to photograph: it has a highly reflective and uneven surface which has caused some difficulty with obtaining a high quality image.  Following a number of discussions on the subject, a decision was made for the photographs to be taken only using print film which is to be developed by hand.  From selected negatives, slides and digitized images can be produced with little loss of quality.

2.2    Data Base
The use of the data base has become more routine, in particular the log book, where individuals can add observations, and record treatment, etc.  In fact this will become a unique document providing a detailed account of the present campaign.  The new images of cross sections (taken with a digital camera) are of a higher quality than those previously taken in slide format which were then scanned, and will greatly facilitate our interpretation and analysis of the paint structure.  It is planned that earlier images of cross sections will be re-taken using the digital camera.  Some minor "glitches" have been reported back to Dr.Nicholas Eastaugh who rectifies these problems with the subsequent monthly upgrade.

3. TREATMENT

The treatment has continued in similar manner to previously, with little variation in the methodology.

3.1     Stabilizing paint, plaster and stone
In addition to using isinglass, an acrylic dispersion (Plextol B500) was used where the entire paint structure is delaminating from the underlying support.  Also, lime grout (Totternhoe lime putty, sieved and diluted in deionised water) applied by syringe or pipette has been added as a support and gap filler, where necessary.

3.2    Reduction of the surface coating
The cleaning of some soluble black lines which appear to exist only towards the upper edge of the painting and on the triangular sections of plaster, have proved problematic.  The cleaning of these areas was initially reliant upon the earlier i.r photography survey.  However, an i.r camera and monitor and has proved an extremely useful aid particularly on areas not covered by the previous survey. In fact , new images have been discovered in the inaccessible corners of the painting.  In tandem with the reduction of the megilp around the black lines, these were coated with a temporary protective layer of isinglass.  Further tests will be undertaken at a later date to determine a method to reduce the megilp over these black lines.

3.3    Tests to remove overpaint from the soffit
Early in the month a series of small tests were undertaken to remove the thick brown overpaint on the soffit.  Three solvent mixtures in thrixotropic gel were tested.  The most effective results were obtained using a commercially available dichloromethane based gel.  However, this raised the issue of stability of the copper based green paint under the overpaint.  Initial research by Dr. Nicholas Eastaugh suggests that there may be a risk of alteration due to a reaction with chlorinated solvents resulting in a copper chloride corrosion product (tenorite).  Further research is currently being undertaken into this question and also into alternative paint removal formulations.  The feasibility of leaving the brown insitu is also being explored.

4.    SCIENTIFIC REPORT

Dr Nicholas Eastaugh visited the site on 1st October.  During his time on site the data base was upgraded with information from initial paint samples and a detailed discussion about the painting.  This resulted in further sampling (134-148) to answer specific questions about the paint structure and technique.  In particular we are looking at the soluble black lines, brown surface layers, a pink/grey preparatory layer, indentifying other areas of Gee's intervention, and other aspects of the original paint technique and subsequent interventions.  

4.1    Results from samples (130-133) collected in September
A fine black layer found over an island of calcium sulphate (130) was probably part of the restoration applied by local artist, David Gee in 1831.  We still do not understand the origin of the calcium sulphate (but there appear to be widespread islands) as we had expected residues of calcium carbonate (limewash).  The irregular brown residue particularly visible on the pale flesh areas after cleaning (131), was initially found to be part of the megilp layer, and was possibly caused by localized irregularity in the preparation and application of the coating.  However, further investigation of this is planned, including GC-MS.
A red lac lake was identified as part of the composition for Christ's crimson robe (132).  Interestingly, a comparable sample was taken from Rubens "Massacre of the Innocents".

A potential complication of the cleaning was the identification of a pale orange colored glaze (133) covering the dark green background and the "mille fiores" decoration.  Fortunately this has been found to be resistant to the cleaning methodology we are using.

4.2    Swab tests
A sequential collection of swabs were taken from five specific areas to determine whether there was a pick-up of pigment during the procedure to remove the megilp.  These were sent for analysis.

5. ENVIRONMENTAL MONITORING

Tobit Curteis (Tobit Curteis & Associates) and Rob Hayes (Colebrooke Consulting Ltd.) who are involved with the environmental monitoring of the painting visited the site.  A wireless system for recording ambient temperature and relative humidity as well as surface temperature and the measurement of i.r and u.v light levels was installed.  Information can be downloaded via a modem connected to the telephone line.  This will build upon the data provided by the initial monitoring undertaken by the Wall Painting Dept of the Courtauld Institute of Art.

6.    PRIMARY OBSERVATIONS

There has been good success with the initial cleaning of the sensitive black lines with the i.r camera and monitor, which has also revealed figures in the top north corner along the vertical edges that were not previously visible.  A second copy of i.r photographs previously taken have also been ordered to help with the cleaning.

7.    PLANS FOR NOVEMBER

The cleaning and stabilization process will continue.  Trials for the soffit require further investigation.  We are expecting the results of sampling and from our swab tests.

 

Grundig electonic camera, Type SN76 and Grundig electronic monitor.  We are grateful to Adrian Buckley and Graeme Barraclough of the English Heritage Conservation Studio for their assistance with this investigation.

 

John Burbidge
4 December 2002


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)



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