Tuesday, July 24, 2012

An Alabaster Alabastron

An archaeological excavation demonstrates the complementary skills of archaeologists and conservators and many others.  Archaeologists are experts in the history and material culture of a site, while conservators are knowledgeable about the materials and techniques used to create art and artifacts as well the steps needed to conserve and restore things. 

The fragments of this alabastron, a container made of alabaster or other materials for holding scented oils, were recovered in several different loci (excavation units) over a few years of excavations.  The archaeologists recognized the significance of the find and gathered the pieces together. 

Before Treatment

Then pieces were then given over to conservation.  After examining and documenting the fragments, I reconstructed the vessel using my favorite adhesive, Acryloid B-72, poly(ethyl methacrylate).  If the alabastron were going on display in a museum, I might have filled the gaps between fragments, possibly with a mixture of B-72 bulked with fumed silica or glass microballoons.  But like on most archaeological excavations, the goal of the conservator is to only stabilize the artifact and make it available for research.  Therefore, replacement of the losses is unnecessary.  Here is the finished alabastron.

After Treatment

Now the object is ready to go back to the archaeologist, who will draw and photograph the object and continue research on its significance.  An alabastron as large as this one (9 cm in diameter and over 13 cm in length) was probably imported; archaeologists can use the find to develop theories about trade and social interactions.

Sunday, July 22, 2012

Preventive conservation at Gordion

Welcome back to another season of Objects Conservation at Gordion.  The team this year is Jessie Johnson, Cricket Harbeck, Julie Unruh in a cameo appearance, and me, Elizabeth La Duc, a graduate student in art conservation at Buffalo State College.  This is my first season at Gordion, and I’m very excited to be here.

In addition to active treatment of finds, a major part of our work is preventive conservation, including maintenance of proper storage conditions to reduce future degradation.  One annual task is renewing the bags of silica gel at the artifact storage depot.  Silica gel is used as a dessicant, just like in those little packets that come with new shoes.  (Silica gel can also be “conditioned” and used as a buffer to maintain a certain humidity).

Silica gel beads

Bags of silica gel are placed with groups of copper alloy artifacts in archival boxes.  Like many degradation reactions, bronze disease, a nasty form of copper corrosion caused by the presence of chlorides, is moisture dependent.  Left untreated, “infected” objects will disintegrate to green powder.  The silica gel maintains a dry environment inside the box, preventing further copper corrosion.  As mentioned in an earlier post, copper alloy objects at Gordion are routinely treated with BTA, a corrosion inhibitor, but a dry environment provides another layer of protection. 

Every year the silica gel bags are taken out and are dried in an oven to renew their moisture absorbing properties.  Some of the silica gel even includes an indicator that changes color when dry.  This year, we have an exciting new purchase for the lab: a new toaster oven.  It’s sold to make borek, a delicious Turkish pastry, but it is working well for silica gel, too. 

Unfortunately not for making pide (Turkish pizza)

Here’s the finished result: the indicator strip placed in the box with the renewed silica gel shows there’s no moisture and that the copper alloy objects are safe for another year.

A dry storage container