Volume 18, Number 1 .... January 1996

Modern Techniques for the Nondestructive Examination of Musical Instruments

by Robert Portillo

Until recently, conservators and musical instrument makers had limited tools for the examination and documentation of musical instruments. These early techniques and tools included observation, measuring tapes, calipers, and mirrors (flashlights being a more recent addition). Currently, new policy in specialist museums has been to encourage the copying of musical instruments in their collections. This makes identification of construction techniques very challenging and demands well documented examples. Fortunately, the conservator now has the use of a new and interesting arrangement of high-tech machinery for non-invasive organological research.

In preparation for making copies of several of the instruments in the UCLA Erich Lachmann Collection, a new nondestructive inspection technique for examining musical instruments was developed. This article will review both Radiography and this new technique, the Remote Visual Inspection System (Borescope) .

In 1895, the first permanent X-ray images photographed by Wilhelm Conrad Roentgen pioneered three applications of x-ray imaging. The first application displayed the contents of a closed container; the second reveals structural defects in metal; and the third produced a permanent x-ray of a part of the human body. Art museums have been employing the use of x-rays in the examination of paintings since the late 1920's. Not until 1949, in the Galpin Society Journal, does Eric Halfpenny's article on "The English 2- and 3-Keyed Hautboy" include radiographs of wind instruments. By the 1970's Friedemann Hellwig (a conservator at the Germanisches National Museum in Nuremberg) had begun to experiment with radiographic exposures of harpsichords at greater distances while using large format paper. In 1976, G. Van de Voorde described the properties of graphic Cronaflex Projection Film B (PBF-4) in an article,
"The Radiography of Rembrant's Night Watch." Currently, Mia Awouter's article, "X-raying musical instruments: a method in organological study" is the most applicable work on the technique.

What are some of the limitations of radiographic inspection of musical instruments and how can the advantages be applied?

The technique is expensive (a resourceful conservator can find a way around this).
"Radiography can detect only those features that have an appreciable thickness in a direction parallel to the radiation beam." (Metal Handbook, V. 17, 297-298). Being mostly three-dimensional objects, musical instruments yield differences in absorption, causing distortion due to parallax.
Large musical instruments require scanning at greater distances, and a large format film.
Because large doses of radiation kill human cells, safety requirements impose both economic and operational constraints on the use of radiography for inspection.

Essentially, radiography is a nondestructive technique for evaluating the internal characteristics of otherwise invisible aspects of an object. In general, the technique provides a useful measure of a musical instrument in the following ways:

The ability to detect internal construction of a musical instrument, including the examination of prior repair work, alterations, and in some cases forgeries.
Significant variations in the structural composition of the instrument reveal the density of materials.
Internal damage by insects is revealed.
Radiographs become permanent records of original inspection data.

The second technique for the inspection of musical instruments is the Borescope. Fundamentally, the Borescope is either a flexible or rigid optic tube which illuminates the worksite with light transmitted through fiberoptics from a light source. Because adapters provide the borescope photographic compatibility with either 35mm still or video cameras, the objective lens at the end of the probe tip gives the conservator easy focusing control and provides a photograph of the original inspection data.

Boroscope

The technique is not expensive.
Displayed on either a video monitor, or directly through the eyepiece lens, one can clearly view the inspection area. (Using an OES scope attachment, from Olympus America Incorporated, makes the image brighter and larger.)
The optic tube is constructed with a covering of PVC which protects the musical instrument from damage. This covering also keeps the diameter small, which is an advantage when examining small or unreachable areas. (The thin fiberscope used was 4.1mm in diameter). Two-way articulation gives the flexible borescope maneuverability and easy access into the interiors of musical instruments.
Significant features of a maker's construction technique, including materials, can be easily indentified.
There is no health risk for the user.

The Borescope in combination with Radiography greatly enhances the potential for nondestructive examination of musical instruments. An instrument maker's construction method becomes visually identifiable in those cases where a radiographic scan may have distorted or penetrated an image.

For example, before the Borescope came to my lab, I had taken radiographs of a Pardessus de Viole by Louis Guersan, Paris 1750.(1) The images were good but they completely missed a significant feature of Guersan's construction technique: the parchment linings near the neckblock assembly (below), which became visible during examination with the Borescope. Several days later, while using the Borescope to examine the interior of a Viola dÆAmore by Thomas Andreas Hulinzky, Prague 1781(2), I noticed what appeared to be a drop of hide glue coming from a nail hole in the neck-block assembly. This is not unusual since many violin makers, from the 17th and 18th- century used nails to fasten and support necks onto the bodies of string instruments. What was unusual was the overall size of the neck-block, making this a perfect candidate for radiography. The radiographic image revealed the reason why the neck-block was so large--it was installed to disguise or cover prior (wood screw) reconstruction of the neck block assembly, a recent consolidation (possibly thirty - forty years old).

Parchment Linings Viola d'Amore Hide Glue Drop

X-radiograph of neck of Viola d'Amore

Since these preliminary inspections began in 1991, thirteen instruments from the UCLA Erich Lachmann Collection of Historical Musical Stringed Instruments have been systematically examined and documented by these technical methods. The two examples above serve to demonstrate how this documentation can provide a structural history of musical instruments for the conservator, making these modern techniques for the nondestructive examination of musical instruments very useful indeed.

(1) A high-treble Viol, the Pardessus was in vogue with the French upper class during the middle eighteenth century, The Pardessus was regarded as a fashionable lady's instrument and uses as an appropriate accessory to their pastoral posing. The Pardessus was no longer in use after the Revolution.

(2) This "English Violet" is the only extant viola d'amore with the configuraion of four playing and five sympathetic strings.

Acknowledgments

I would like to thank the J. Paul Getty Museum, the Getty Conservation Institute and members of the scientific program: Dr. Dusan Stulik, Michael Schilling, and Cecily Grzywacz for their continued interest in the Lachmann collection and loan of the Borescope. UCLA Department of Radiology's Technologists and Technicians: Vinis Batta, Randolph C. Jones, Patrick Hale, and Miguel Lansangan who responded with great enthusiasm throughout this project. Finally, to the UCLA Department of Music and Dr. Jon Robertson, Chairman, for permission to print photographs of instruments in the Erich Lachmann Collection.

Materials

Olympus America Inc., Industrial Fiberoptics Division 4 Nevada Drive Lake Success, NY 11042-1179 800-446-5260

Recommended Radiography Technique for Stringed Instruments

AP (anterior/posterior): 41KVP (kilovolt peak) @ 12 mas, ASA 100 extremity film @ 46ö Lateral X-ray: 43 KVP @ 15 mas, ASA 100 extremity film @ 46ö

Bibliography

Awouters, Mia. "X-raying musical instruments: a method in organological study," Revue belge de Musicologie/Belgisch Tijdschrift voor Muziekwetenscha, XXXVI-XXXVIII, 1982-1984. 207-215.

Halfpenny, Eric. "The English 2- and 3-Keyed Hautboy," The Galpin Society Journal, II, 1949. 10-26.

Helwig, Friedemann. "Die rontgenografische Untersuchung von Musikinstrumenten," Maltechnik Restauro, 2, 1978. 103-115.

Nitske, W. Robert. The Life of Wilhelm Conrad Roentgen, Discoverer of the X-ray. University of Arizona Press, 1971.

Tsang, Jia-Sun; Ravenel, Nancie; Berstein, Johanna; and Odell, Scott. "The Conservation of The 100,000th Steinway Piano," CLEANING RETOUCHING AND COATINGS Technology and Practice for Easel Paintings and Polychrome Sculpture, ed. by Mills, John S. and Smith, Perry, in IIC Preprints of Contributions to the Brussels Congress, 3 - 7 September 1990. 52 -55.

Van de Voorde, G. "The Radiography of Rembrandt's Night Watch," Bulletin van het Rijksmuseum, 24, 1976. 52-67.

Author Robert Portillo has been Curator of the UCLA Erich Lachmann Collection of Historical Stringed Musical Instruments, 1989 - 1994, and is currently a musical instrument builder/conservator in private practice. All photos are courtesy of the author.

This article is an expanded version of a presentation given at the 1992 WAAC Annual Meeting, September 27-29 in Santa Fe, New Mexico.

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