El cartonaje finalmente se relaja

por Teresa Jiménez-Millas

Durante el pasado mes, he tenido el privilegio de poder trabajar en un cartonaje egipcio, y ¡no menos es la suerte que tengo de poder escribir este artículo en mi lengua materna! Me han consentido mucho en este equipo.

Poco o nada sabemos de la procedencia de la obra, fue una donación a la colección egipcia del museo por parte del Sr. Thomas A. Scott en el siglo XIX, y es un estupendo ejemplar para estudiar tanto la técnica del cartonaje como el tipo de intervenciones que se hacían en el pasado.

La nomenclatura es una derivación del francés “cartonnage”, término usado en egiptología para hacer referencia a la técnica en la que finas capas de yeso se aplicaban sobre un soporte que podía ser fibra (lino) o papiro, permitiendo la flexibilidad suficiente para moldear y obtener las formas deseadas de la silueta del difunto, algo parecido al papel maché para que os hagáis una idea. Sobre este aparejo de yeso se elaboraban la policromía y el dorado.

Esta pieza ocupaba la zona pectoral de la momia. La imagen representa una figura alada con el disco solar sobre la cabeza, posiblemente Nut, quien junto a su hermano Geb eran los padres de Isis, cuya historia es central en la resurrección de los extintos.

En cuanto al proceso de restauración de esta obra, lo primero que nos llamó la atención fue el soporte adherido al reverso, que no formaba parte del original, y por otra parte el gran número de fracturas y pérdidas que presentaba el anverso.

Por la tipología de esta obra sabemos que no era plana y que tenía cierta curvatura, pues su función era decorar y descansar en el pecho de la momia. En este caso, parece que la persona que intervino la pieza en el pasado no tuvo en cuenta esto y añadió un cartón con mucho adhesivo en el reverso, de manera que la pieza ¡quedó completamente aplanada!

En este tratamiento de conservación lo fundamental era eliminar ese soporte trasero para relajar la obra, pese a que esto supusiera que los fragmentos antes unidos quedaran sueltos y desprendidos. Este paso se hizo mecánicamente con la ayuda de un bisturí y bajo las lentes del microscopio.

Se quiso evitar cualquier contacto con un medio acuoso, pues ante una obra tan frágil cualquier fluctuación de humedad podría afectar negativamente al soporte, a las capas pictóricas y al dorado.

Con el paso de los días se pudo observar cómo cada fragmento iba recuperando su forma primigenia, recobrando cierta curvatura y relajándose. Esto determinó el resto del proceso, pues se decidió no forzar la unión de las diferentes áreas. Cada una presentaba en este momento un diferente perfil y tratar de reunirlas provocaría mucha tensión innecesaria.

Se consolidaron y protegieron todas las zonas por el reverso y se estudió la mejor manera de realizar un soporte para cada una de ellas que permitiese también su futuro montaje y exposición.

Tras muchas pruebas, preguntas y mucha paciencia de mis colegas, se decidió que lo mejor sería hacer tres soportes para las tres áreas con resina epoxídica de madera; de esta manera cada uno soportaría un fragmento, un planteamiento respetuoso para la obra que nos hace entender que el paso del tiempo y las intervenciones del pasado dejan su huella.

Photos showing various trials for constructing a support for the fragile cartonnage pieces. The support in the third image (far right, made of wood epoxy) was the winner.

Tengo que agradecer a Jane Williams, jefa de conservación y restauración del “Fine Arts Museum of San Francisco” por sus consejos y su ayuda inestimable para el tratamiento de esta obra que tanto respeto me causaba.

Con mucha gratitud por haber tenido la suerte de trabajar con tan generosas personas y haber aprendido tanto en este fantástico proyecto, ¡espero algún día poder ver este cartonaje expuesto en el museo!

Este proyecto ha sido posible en parte por el Instituto de Servicios de Museos y Bibliotecas.

Should one strike when the solder is hot?

By Tatiana Perez

I am an undergraduate Classical and Near Eastern Archaeology student at Bryn Mawr College and this past summer, I began as a conservation intern within the Penn Museum’s Museum Practice Program. I am continuing this work through an independent study in the Museum’s Conservation Department this Fall. During my time here, I have treated a group of Egyptian faience shabtis.

Egyptian faience shabti prior to treatment.

Shabtis are statuettes that were made to be placed within ancient Egyptian burials for the purpose of assisting the deceased in the afterlife. The shabtis I worked on are made of Egyptian faience, a material made from silica, alkaline salts such as plant ash or natron, lime, and metallic colorants. The faience could be hand-shaped or pressed into molds, that when fired, would self-glaze. Although faience was made in many different colors, it is most often associated with a bright blue/turquoise color (using a copper colorant) as seen in many amulets, beads, and figurines.

The specific group of shabtis I worked with this summer differed in size, shape, and color. Many were previously repaired and some of these old repairs were failing. Unfortunately, these objects had become disassociated from their accession numbers and records, so there is no information on their provenance or previous conservation treatments. I was tasked with documenting their condition, and treating those that were broken or in need of re-treatment, either to remove failing old adhesives or remending those that were previously mended but now broken. As adhesives age, especially those used in the early 20th century, they can become discolored, may shrink or expand, or may become stronger. All of these conditions pose problems to the objects that can affect their future stability and ‘health’.

Since no record of the treatments existed, I used various methods to determine what worked best to remove the adhesives that were used. First, I used UV light to identify the type of adhesives. After observing that it was possibly shellac or animal glue, I spot-tested the adhesives using a variety of solvents. I found that acetone, ethanol, and deionized water worked best, so I left the shabtis in acetone vapor chambers for a few hours to allow the adhesive to dissolve.

After the old joins were taken down, one particular shabti caught my eye immediately. This lighter green-blue shabti had metal adhering one of the joins, with some adhesive underneath as well. After consulting with various conservators about this unexpected find and with help from the handheld pXRF instrument, we found that it was lead solder that was used to join these pieces. This is a very unusual (and outdated) technique for mending pottery and as head conservator Lynn Grant said, it’s likely whoever treated it last “struck when the solder was hot”.  In other words, the person who last treated this object might have used the solder because it was nearby and ready to use. This conservation method was not the best way to mend the shabti and doesn’t reflect current methods we use. The body, or core, of faience objects is very porous and absorbs whatever adhesive is applied. When the solder was applied it seeped into the body of the body of the object, and made it very difficult to remove.

Lead solder between first and second fragment (top). 60X magnification of the lead solder (bottom).

Though this conservation treatment doesn’t affect our understanding of the shabti, it got me thinking about how conservation ethics and practices have changed over time. As stewards of cultural heritage, conservators have the important job of fixing objects in a way that is reversible and that doesn’t compromise the object’s cultural integrity or future use. Conservators do their best to maintain the integrity of objects, for both research purposes and to preserve a piece of the culture these objects came from for future study and display. This means that conservators must also apply these ethics to objects that were treated before these standards were enforced, and take caution to prevent any further loss of information no matter how small.

With the shabti group I worked on, I used a technique that is commonly used to repair porous or low-fired ceramics. Before using an adhesive to repair the fragments, I applied a low concentration adhesive solution on the break edges to create a less porous surface and to prevent the adhesive from seeping into the body of the faience. I then used a higher concentration adhesive to put the pieces together. This specific treatment is reversible and will ideally last a century or more!

Mending artifacts can be a slow process in which a conservator attaches one piece a day. While working on this small group of shabtis for many weeks, I’ve grown very attached to them. They are all unique pieces with their own quirks, and I can’t wait to see them back together and ready for future use.

Shabti group after treatment (left). Shabti after treatment (right).

A lion relief from Nippur

Yesterday we received a new artifact in the lab: this terracotta lion relief from Nippur, Iraq.

B20014: the lion relief in fragments

Some may argue that this object could be a candidate for the Ugly Object of the Month club. Well, we like him, and one of our conservators pointed out that he looks a lot like one of these wonderful characters from William Steig’s Rotten Island.

Illustration from William Steig’s “Rotten Island”. Image courtesy of scienceblogs.com

This relief was excavated in the University of Pennsylvania’s Babylonian Expedition to Nippur in 1899. Like the Nippur slipper coffin currently on display in the Artifact Lab, it was previously repaired with metal staples and (at least one type of) adhesive, likely around the same time as the slipper coffin.

The staple-like wire tires used to repair the relief are visible in this view of one of the break edges.

More evidence of the old repairs on this fragment.

Getting this relief ready for exhibition in the Middle Eastern Galleries will not only require significant conservation treatment, but also a custom mount so that it can be displayed safely. We will provide updates as we work on this.

’tis the season for…removing BJK dough

I had heard about this material, BJK dough, since graduate school but had never actually seen it on an object until coming to the Penn Museum. Now that I’ve encountered it, I know it when I see it. It’s often found as fills on ceramics in our collection that were treated in the 1970s and 80s. It’s brown, fibrous, and really hard. Sometimes it is painted but in some cases it is left unpainted because its brown, matte appearance worked well for filling archaeological ceramics (and other similarly-colored objects).

I first read about BJK and its predecessor, AJK, in this great JAIC article by Steve Koob, Obsolete Fill Materials Found on Ceramics. AJK was developed in the University College London (UCL) conservation lab in the 1960s, by mixing Alvar (polyvinyl acetal), jute, and kaolin in solvents, to create a putty. In 1980 Alvar was discontinued so was replaced by Butvar (polyvinyl butyral), to make BJK dough. Both AJK and BJK were used extensively in conservation labs during these decades to fill ceramics and for other gap-filling on objects. Some fills were made by creating a lattice-support with narrow strips. This terrific blogpost goes into detail about AJK and BJK and includes a recipe for making strips of dough for filling archaeological ceramics. This recipe is interesting for understanding the old treatment materials and methods, but just to be clear, is NOT recommended for conservation treatment any longer. We use materials that are now known to have better long-term aging properties, such as Paraloid B-72 bulked with glass microballoons.

Here are some examples of BJK dough that we’ve found on objects that are currently in the Artifact Lab:

31-17-318, painted ceramic vessel from Ur, before treatment (left) with painted BJK fills, and during treatment (right) with BJK fills removed. One of the removed BJK fills is pictured in the center.

73-5-557, Detail of iron sword from Hasanlu (Iran) with BJK fills (before treatment)

E8436, cup from Karanog, Nubia, Meroitic Period (ca. 100 BCE-300 CE) with large painted BJK fill. The black arrow points to a new crack that developed in the ceramic due to shrinkage of the BJK fill post-treatment.

Due to damage that we have observed on objects with BJK fills (see image above), and to prevent damage from occurring in the future, we often remove BJK when we find it on objects being treated in the lab. Fortunately, the BJK can be removed by poulticing with acetone, which causes it to become flexible and gummy enough to be scraped or gently pried away from the original object.

I think I can safely say that all of us in our department have done our fair share of picking off BJK from objects. Spending time undoing old treatments allows us to reflect on these past treatment choices and on our own decisions. We are very fortunate today to be able to learn from past treatments, to have decades of research and published observations to rely on for our own decision-making, and to have the technologies to allow us to better track condition of objects and materials over time.

As it is, this is a good time of year for reflection, but also to look forward to a new year ahead, and the certainty of new challenges and discoveries to be made. There will be no public access to the Artifact Lab from December 31 until April 8, but we will continue to update the blog as we work in the lab on new projects. Stay tuned, and Happy New Year, from all of us in the Conservation Department!