Andrew Oddy
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RESEARCH PROJECTS

THE CONSERVATION OF MARBLE SCULPTURE

In the early 1960s, the British Museum began an extensive programme of cleaning its collection of classical marble sculptures by the application of a solvent to remove atmospheric grease and a mud-pack to suck out dirt from the porous surface.  The mud-pack consisted of a natural clay-like material called Sepiolite, and the procedure was known as the Sepiolite Method.[1] By 1966, much of the reserve collection of marbles had been cleaned and only the Elgin Marbles remained.  These were, however, a sensitive issue because of the cleaning scandal in the late 1930s when craftsmen had over-enthusiastically scraped at natural deposits on some of the surfaces with copper tools.[2][3]  When the scandal broke it led to the retirement of the Keeper of the Greek and Roman Antiquities Department (on medical grounds!) and the resignation of an Assistant Keeper who chose to leave the museum rather than loose seniority.  memories of this incident were still remarkably fresh in 1966 and the masons' assistants who had been doing the routine cleaning thus far were reluctant to continue with the Elgin marbles.  Test cleaning was carried out by Andrew Oddy and a senior conservator called Hannah lane who demonstrated that the Sepiolite Method did not adversely affect the marble.  What it did do was to leave the surface looking rather 'milky' as a result of the removal of dirt from the porous surface.  It was thus decided to apply a very dilute solution of a water-soluble polyethylene glycol wax.[4]  Because it is water-soluble, it is easily removed, but this did not stop a conservation scientist in Greece alleging that the British Museum had impregnated the Elgin marbles with plastic!

[1]   Hempel, K F B, Notes on the Conservation of Sculpture, Stone, Marble and Terracotta, Studies in Conservation 13 (1) 34-44

[2]   Jenkins, I, Sir, they are Scrubbing the Elgin Marbles, Minerva 10 (6) (1999)  43-45

[3]   Jenkins, I, What happened to the Sculptures of the Parthenon in the 1930s?, Minerva 11 (20 (2000) 9-15

[4]   Oddy, W A, The Conservation of Marble Sculptures in the British Museum before 1975, Studies in Conservation 47 (3)  145-154

 

THE CONSERVATION OF LIMESTONE SCULPTURE

At the same time that the Classical Marble Sculpture was being cleaned by the Sepiolite Method to remove the dirt deposited by the polluted atmosphere of London over many years, a programme was started to clean the Egyptian Limestone Sculptures for the same reason.  In other museums this had been successfully carried out by prolonged soaking in water and this method was adopted at the British Museum.  However, after a few sculptures had been successfully cleaned in this way, the surface of one sculpture started to exfoliate within a very short time after immersion.  The washing programme was stopped  and the sculpture examined to try and determine why the washing treatment had failed in one case but had been successful in others.  Chemical analysis quickly established that the surface of the limestone had become partly converted to gypsum (calcium sulphate) by the reaction of air pollution with the natural calcite (calcium carbonate) of the stone.  The next question was to determine why the surface of some stones were unstable when immersed in water and others not.

At this point it was realised that the stone whose surface had flaked had come from Thebes (in Egypt) while those sculptures that had been washed successfully  had come from Memphis.  Analysis showed that the Theban Limestone contained about 10% of acid-insoluble matter - mainly quartz and clay minerals - and that the Memphis Limestone was relatively pure calcium carbonate (>99%).  Further analysis showed that not only was the purity of the limestone important, but also the presence of soluble salts in the stone - mainly sodium chloride.

the result of this research programme was that following analysis of a sample of the sculpture for acid-insoluble resifue and the percentage of soluble chloride it was possible to predict whether it would be safe to wash the sculpture.[1]

[1]   Oddy, W A, Hughes, M J, and Baker, S, The washing of Limestone Sculptures from Egypt and the Middle East, Revue Lithoclastia 2 (1976) 3-10


THE CONSERVATION OF WATERLOGGED WOOD

In the autumn of 1970, dredging operations in a drainage channel on the Graveney Marshes on the north Coast of Kent revealed the remains of a small ship, the wood of which was completely waterlogged.[1][2]  The National maritime Museum decided to recover[3][4] and conserve the remains of this early medieval boat and asked the Research laboratory of the British Museum foe assistance.[5]  This led to a programme of research into the conservation of waterlogged wood.[6][7][8]  The result was that the method chosen to conserve the 'Graveney Boat' was the replacement of the water inside the wood with a water-soluble polyethylene glycol wax by soaking the timber in tanks of the wax for many months. Tanks were constructed at the national maritime Museum to conserve the boat.[9]

[1]  

THE DEVELOPMENT OF THE SPECIFIC GRAVITY METHOD FOR THE ANALYSIS OF GOLD ALLOYS AND ITS APPLICATION TO THE STUDY OF THE DEBASEMENT OF GOLD COINAGE

THE GILDING AND SILVERING OF OTHER METALS IN ANTIQUITY

JEWELLERY TECHNIQUES IN ANTIQUITY (MAKING WIRE AND APPLYING NIELLO)

TOUCHSTONES AND ASSAYING IN ANTIQUITY

THE SCIENTIFIC EXAMINATION OF ANTIQUITIES

THE APPLICATION OF CHEMISTRY TO THE CONSERVATION OF ANTIQUITIES

TESTING OF MATERIALS FOR THE EXHIBITION AND STORAGE OF MUSEUM OBJECTS (THE 'ODDY TEST')

EARLY ISLAMIC COINAGE

BIOGRAPHIES AND THE HISTORY OF MUSEUM CONSERVATION


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