On 12/09/2019 06:54 AM, mollygleeson wrote:
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.
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.
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.
-- Sent from my Linux system.