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A Preliminary Report on the Relative Effectiveness Of Ultrasonic Cleaning Versus Soaking in the Conservation of Clay Tablets

Published online by Cambridge University Press:  07 August 2014

Brian Lewis
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Extract

This paper reports on an attempt to apply the technology of ultrasonic cleaning to the conservation of clay tablets and to measure the effectiveness of ultrasound against the desalting technique now in use. It is hoped that the results of these preliminary experiments will inspire a thorough investigation into the possible advantages of employing an ultrasonic cleaning system. The author would not recommend switching from the standard soaking method to ultrasound before a good deal more study.

The conservation of cuneiform tablets involves the removal of water-soluble and less soluble salts present in the clay. This is usually accomplished by baking the tablets to approximately 1500° F and later washing them in cool, circulating water. Salt deposits that are not removed through conservation tend to crystallize, damaging the surface of the tablet with its inscription and causing internal disintegration as well.

Type
Research Article
Information
IRAQ , Volume 43 , Issue 1 , Spring 1981 , pp. 76 - 78
Copyright
Copyright © The British Institute for the Study of Iraq 1981 

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References

1 See Organ, R. M., Design for Scientific Conservation of Antiquities (London, 1968), 201 Google Scholar; and Bateman, C. A., “The Treatment of Cuneiform Tablets in the British Museum”, Preservation and Reproduction of Clay Tablets and the Conservation of Wall Paintings, Colt Archaeological Monograph Series, III (London, 1966)Google Scholar, esp. 17.

2 The idea of using an ultrasonic cleaning unit to remove surface impurities from clay tablets was suggested to me by Dr. Bernard Jerome, D.D.S., in the course of a conversation precipitated by his keen interest in Biblical and Near Eastern Studies. In addition, Dr. Jerome graciously volunteered his private ultrasonic unit for, so far as I know, the first test of the effects of high frequency sound on a cuneiform tablet. I owe a special debt of gratitude to Dr. Elizabeth R. Jewell, Assistant Curator of the Yale Babylonian Collection, for her technical advice and assistance. I also wish to thank Prof. Stephen J. Lieberman of the University Museum, Philadelphia and Miss Judy Giordan of the Chemistry department of the University of Maryland for their many helpful suggestions.

3 For a discussion of ultrasound and its practical applications, see Blitz, Jack, Fundamentals of Ultrasonics, and ed. (London, 1967)Google Scholar; and Ensminger, Dale, Ultrasonics, The Low- and High-Intensity Applications (New York, 1973)Google Scholar.

4 I am very grateful to Prof. William W. Hallo, Curator of the Yale Babylonian Collection, for generously underwriting the cost of testing and for permitting the use of previously unaccessioned tablets from the Collection in these experiments.

5 The break appeared to be of recent origin, and one assumed that the percentage of salt by weight would be nearly the same in both fragments. An Ur III tablet was chosen simply because of its availability. It measures 3.6 cm × 3.4 cm × 1.1 cm; its provenance is Drehern. The tablet has now been accessioned into the Yale Babylonian Collection (YBC 16556).

6 The tests were conducted at the Baron Consulting Co., Milford, Connecticut under the supervision of Dr. Harry Agahigian, Ph.D., Chief Consultant.

7 At a temperature of 128° F and a frequency of 80 kHz.

8 By one-half to two-thirds of the time spent in soaking. Recent findings indicate that increasing the temperature in the ultrasonic unit to 130° F will accelerate the rate of reaction and reduce the period of salt extraction to one-fourth of the time required by soaking.

9 Some concern has been voiced that ultrasonic treatment might damage or destroy poorly preserved tablets that soaking would not. In an attempt to determine the effects of ultrasonic cleaning on fragile and friable tablets, a number of fragments from broken tablets were treated by both methods for purposes of comparison. The fragments were all in poor condition, and if one piece was judged to be more brittle than its counterpart (from the same tablet), it was placed in the ultrasonic group. There was not one instance where a soaked fragment showed less deterioration after cleaning than the fragment from the same tablet that was treated ultrasonically. The author intends to publish the complete results of all his tests at a later date.