The Conservation of an Egyptian “Whistle”

The blog post for this week is written by Alice Law, who has just completed her first year studying MSc Conservation Practice at Cardiff University. Alice graduated from Cambridge University with a degree in History of Art in 2017, and spent several years working in a Lower School before coming to Cardiff last year.

In October 2020, wide-eyed and inexperienced in the world of conservation, I began my Masters degree in the middle of a pandemic. At Cardiff University, the MSc in Conservation Practice is a conversion course, meaning that people from many different walks of life and levels of experience can take it. A lot of us enter the degree with little or no experience of conservation. I think everyone this year can say that studying for a degree with COVID restrictions has been a challenge, but we were lucky to be able to have some in-person teaching in the lab. As part of the course, we have the privilege of being able to work on real objects from museums, and my very first assigned object was an Egyptian “whistle” (W247), broken into three pieces (fig. 1). I have been fascinated by Ancient Egypt for as long as I can remember, so the chance to work on an Egyptian piece was thrilling.

Fig. 1: Pre-treatment photograph, October 2020.

My excitement only grew when I first saw the whistle, after tentatively removing the sheet of foam, beneath the lid of the unassuming little storage box sat in front of me on the desk (fig. 2). The three pieces each lay cradled in their own nest of tissue paper, consisting of an internal copper tube, with a mouthpiece at one end, and blue (lapis lazuli) and white (most likely ivory) alternating rings along what would be its length. I was especially taken aback by the vibrancy of colour on the whistle—I had not known what to expect, but I was not expecting this. I had never seen anything like it. Excitement soon became mingled with the worry that probably every conservator feels at some point, as the monumental task of figuring out how to stick the three pieces back together now loomed ahead.

Fig. 2: The three pieces of the whistle in October 2020.

The first part of any conservation project is the initial observation of an object. Before applying any kind of treatment, you need to have an understanding of the object: what it is (or what could it be), what is it made from, how could it have been made, and what contextual significance might it have? However, because of the nature of the conservation field, simple answers—or any answers at all—are not always available, the information that you can gather comes together to form a complex picture of the object, with factors that need to be balanced with one another to find a navigable route through the process of treatment. A few things stood out. There was the obvious need to reattach the three pieces back into one object. Most of the rings looked stable, as did the mouthpiece, and I wanted to establish if the central tube was stable or if it was corroding. There were also several areas with old adhesives, most likely from previous repairs—some yellowing globules, and some grey masses in the centre of one of the tubes, which may need to be removed.

After research into copper corrosion (fig. 3), I was able to say that the corrosion was indeed stable and started to focus my attention on how the pieces could be reattached. The problem was that the tube was so fragile. In some areas, it was in pieces, being held in place by the previous repairs. Other matters to contend with were that the joints did not line up cleanly, and using an adhesive on such as small surface area as the rim of the tube would most probably not hold the whistle together for very long, and may even break the tube further. It became obvious early in the process that a successful join would also involve internal support. The two main options were using a dowel or a filler, but after talking my ideas through in the Lab, I eventually decided on using an adhesive as a filler rather than a solid dowel, which could damage the inside of the tube.

Fig. 3: Microscope image of the top piece of the whistle. A red cuprite (cuprous oxide) layer against the metal, topped with a green malachite (copper (II) carbonate) layer commonly appear on copper objects, and can even help to prevent further corrosion. In these cases, removing it may cause more harm than good.

 

The next step in treatment was to decide on what the adhesive and filler would be. After more research and some tests in the labs (fig. 4), I decided on Paraloid B-72 and microballoons. B-72 is an acrylic polymer that has displayed good aging properties. Another big factor in its favour was that it remains soluble in acetone, so can be removed if necessary, such as if the fill ever breaks. Similarly, microballoons are tiny glass bubbles, which, when mixed with an adhesive, add volume to it. I tested a handful of possible fillers, including powdered slate, talc, and marble dust, but microballoons were the best option. They mix to a smooth consistency with the B-72, and produce a light filler, meaning that unnecessary weight is not added to the fragile object. If something happens to the join, it will hopefully be the adhesive that breaks rather than the metal tube, which is always what you want an adhesive to do.

Figure 4: Samples of test fillers. 40% Paraloid B-72 in acetone and fillers were mixed together and shaped into little rods to mimic the rough size and shape of the fills that were needed.

After a little readjustment of a small metal fragment on one of the pieces, the exciting, yet nerve-racking day soon arrived to add the first fill to the whistle. As carefully as I could, I dampened the B-72/microballoon mixture and packed it down into the tube of the top and middle whistle pieces until there were little pieces of filler emerging from each section (fig. 5). With slightly shaking hands, I pressed the pieces together to form a join. The join would need a little adjusting in the following weeks, but it was an important, and thrilling, step forward in the treatment.

Fig. 5: Filling and preparing to reattach the top and middle pieces.

                  

The third piece was reattached in the same way a couple of weeks later, and there sat a single whistle curing in the sand tray (fig. 6). After months of work, it felt like a massive achievement, but there was still a lot of work to do. The next job was to remove some of the old adhesives. I was the second person to work on the whistle at Cardiff, and much of the previous adhesive had already been removed from its surface. Now that the whistle was back together, I could remove some of the remaining pieces.

Fig. 6: The reattached whistle.

Fourier Transform Infrared Spectroscopy (FTIR) is a useful analytical tool that conservators can use to identify substances. It works by passing infrared radiation through a sample, and causing chemical bonds within the structure to vibrate in different ways, thus producing a spectrum with peaks denoting certain chemical bonds. The analysis carried out in the previous year had revealed that the yellowing adhesive was polyvinyl acetate/polyvinyl chloride, which meant that I was able to use acetone and a cotton swab to carefully remove the remaining pieces on the object. I had also carried out my own analysis on the mysterious grey substance inside the tube. FTIR results are most effective at identifying single substances, and are not as reliable with mixtures, but there were areas in the spectrum that indicated a proteinaceous substance—gelatin/collagen, suggesting that animal glue was included, with another substance—perhaps plant gum or plaster of Paris, which was more difficult to identify for someone new to the process. With this information, I decided to leave the substance inside the tube, because there was a far greater risk of its removal damaging the whistle, than leaving it where it was.

Once the adhesive had been removed, I turned my attention to inpainting the very obviously white fills (fig. 7). I used acrylic paint and a wide range of colours to get as close a match as I could to the surrounding metal. It is amazing how many colours go into a match—I ended up using raw umber, yellow ochre, venetian red, turquoise, black, and white to match the uneven, undulating tone of the metal and its corrosion. Once finished, it is my hope that if casually walking past it on display, the fill is invisible, and may only be subtly visible if you know where to look for it.

Fig. 7: The largest fill in the process of being painted.

By this point, the conservation process was nearly complete, aside from some final cleaning of the rings and the consolidation of the black, bituminous substance on the tube near the mouthpiece, which had started becoming detached during treatment. I kept the samples that had detached for use in future analysis, and consolidated the remaining substance on the tube with Paraloid B-67 (another acrylic polymer with good aging and yellowing properties) to prevent it from being lost over time. The final task was to reattach the label (on acid free paper) inside the bottom tube and then the treatment was complete (fig. 8)!

Fig. 8: Post-Treatment Photography, May 2021

It was a certainly a challenging object to work on as my first ever conservation project, but I hope I did it justice. The whistle itself is a mysterious object—its history before its time in the MacGregor Collection is unknown (for more, see the earlier blog post), and its use unclear—but it was a privilege to be able to work on such a fantastic piece, to add another layer to its enigmatic history, and to be part of allowing future visitors to see and enjoy what it has to offer.

Bibliography:

Canadian Conservation Institute. 2007. Recognizing Active Corrosion – Canadian Conservation Institute (CCI) Notes 9/1 - Canada.ca. Available at: https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/recognizing-active-corrosion.html [Accessed: 17 November 2020].

Down, J. 2014. ‘The evaluation of selected poly(vinyl acetate) and acrylic adhesives: A final research             update’, Studies in Conservation 60(1), pp. 33–54.

Scott, D. 2002. Copper and Bronze in Art. Los Angeles: Getty Publications.

Wolfe, J. and O’Connor, T. 2005. ‘Properties of fillers in putties based on Acryloid B-72’, in Proceedings of the Objects Specialty Group Session, June 11–12, 2005, 33rd Annual Meeting, Minneapolis, Minnesota. The American Institute for Conservation of Historic & Artistic Works, pp. 91–117.

Young, C. et al. 2002. ‘The mechanical behaviour of adhesives and fillers for re-joining panel paintings’, in National Gallery Technical Bulletin 23. London: Yale University Press,   pp. 83–96.