Saturday, July 5, 2014

A Salty Phrygian Trefoil Jug

Posted by William

We started this season at Gordion with a condition survey of the collection on view at the Gordion Museum. This survey of the museum collection occurs on a yearly basis to allow condition comparison with previous years.  This year during our survey a trefoil ceramic jug had developed the presence of salts, a common problem with some archaeological materials.  The ceramic was excavated in 1965 and found in a secondary pit.  It dates to the Middle/Late Phrygian period (7th – 4th century B.C.) and would have likely been used for pouring liquids.  The jug was taken off view and a condition report was recorded and before conservation treatment images were taken.  
Before Treatment

Before Treatment
Before Treatment Interior
Taking Before Images
The desalination of ceramic materials involves removal of soluble salts acquired from archaeological burial conditions, manufacture and use, and previous conservation treatments.  Soluble salts typically appear as white efflorescence on the surface of the ceramic body.  Their removal is necessary for preservation of the ceramic due to their harmful characteristics.The previously restored fill in the ceramic was removed before desalination.  This was done carefully using a scalpel as well as dental picks.  The decision to keep the plaster fill was made as it was in great shape and was not causing damage to the object.  In order to remove the fill safely it was necessary to cut it into two pieces.  Excess plaster on the inside of the vessel was also removed.  After the fill was removed the ceramic was ready for a desalination treatment.  
Removing the Restored Fill
One Section Removed
The general technique for removal of soluble salts involves soaking the object in less contaminated water, so that concentrated salts in the object diffuse out into a less concentrated solution.  In order to carry out the desalination treatment, a source of deionized water is needed. The tap water on site has high conductivity and must be treated to remove minerals prior to use in desalination. This is done using a deionizing column onsite. 

Making Deionized Water
Vessel in Water

To determine the endpoint for desalination an adjusted conductivity measurement (a number representing a conductivity reading adjusted to take into account the ceramic weight and volume of water) is made by entering the data into an equation.  It was determined that soaking the ceramic in deionized water for three days was sufficient for the removal of salts.

Measuring Conductivity of the Water

Entering the Data in the Equation

The ceramic was removed from the desalination bath and allowed to dry overnight.  The edges of the vessel were then cleaned using a dental pick and the restoration paint was removed from the plaster fill.  

After Removal from Deionized Water

Removing Excess Plaster from the Edges

Removing Restoration Paint from Plaster Fill
The plaster fill was reattached by first holding it in place with tape and a padded close pin.  Small bridges of glass microballoons in paraloid b-72 were used to secure the fill to the ceramic and the remaining areas were then filled using microballoons in b-72. 

Reattaching Plaster Fill

After the fill was replaced it was sanded to make a smooth transition between the microballoons and plaster fill.  A small incision was made around the fill to identify it as a restoration and a primer coat of paint was applied.  

After Reattaching Fill
Liquitex acrylic paints were used for inpainting the restoration.  After conservation treatment images were taken and the trefoil jug was then returned to the exhibition case in the Gordion Museum. 

After Treatment Image

After Treatment Image 

After Treatment Image Interior
Phrygian Trefoil Jug Back on View in the Gordion Museum

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

Tuesday, July 12, 2011

Site Conservation at Gordion

Gordion site conservators at work. Photo by Andrea Berlin.

An average visit to Gordion will include three stops: the museum, the Midas Tumulus, and the site located on the mound. For the last few seasons, Frank Matero and his students at the University of Pennsylvania programs in Architecture and Historic Preservation have been diligently working on preserving the site.

This season, site conservation projects include the installation of viewing pavilions, documentation, soft capping, and stabilizing the stone walls of the site. Objects conservation intern Lily Doan was able to join the site conservators for a day of injection grouting.

Here are some highlights from this season's site conservation projects:

The viewing pavilions, constructed from locally purchased
metal pipes and fabric, provide much needed shade for
visitors to the site.

UPenn students document the site. Photo by Andrea Berlin.

Locally produced mud bricks drying in the hot Turkish sun.
These bricks are a component of soft capping, a system where
the introduction of moisture, which may cause damage to the
stone walls, is regulated with plants installed on top of the wall.

Site conservator Alex Lim sifting lime in preparation
for grouting. Photo by Andrea Berlin.

Meredith Keller, site conservator, mixing the grout.

Objects conservator Lily Doan uses an air compressor to 
clean cracks in preparation for grouting.

Wednesday, July 6, 2011

Tomb Monkeys

The entrance into the Midas Tumulus
In addition to working on the artifacts in the Gordion Museum and in storage we also do some work in the fabulous wooden tomb chamber inside the Midas Tumulus. The Midas Tumulus is one of the archaeological resources open to the public in and around the village of Yassıhöyük.  Located across from the Gordion Museum it gets up to 60,000 visitors every year.

This year there are been a project to view features on pitched roof of the tomb and we have been working with the archaeologists who are carrying out the project to document the activity.

Documenting work on the roof of the 2700 year old tomb
Working on and around the tomb chamber involves some rather acrobatic maneuvers. Also being inside a fence and at times viewed by visitors gives a rather interesting flavor to the work- thus the term "tomb monkeys" has developed to describe the archaeologists working in the tomb day after day.

Silverback tomb monkey imparting advice to his assistant
We are also continuing environmental monitoring of the tomb to ensure that visitation, archaeological documentation activities and any unknown problems don’t create an environment that would endanger the wooden structure. This project, on-going for over a decade, has shown that there are small changes in temperature and environment that track what’s going on outside. The changes are slight and the ancient wooden structure (so far) is not in any danger from theseagents of deterioration.

Looking at 2010-2011 datalogger data
Tomb monkeys headed home after a long day 

Monday, July 4, 2011

Road Trip to Hittite Sites

From left to right:
Cybele Tom (NYU Conservation Program, Sardis Conservation Intern)
Jessica Pace (NYU Conservation Program, Sardis Conservation Intern)
Alex Lim (Research Fellow, UPenn Architectural Conservation Laboratory)
Lucas Stephens (Doctoral Student, UPenn AAMW Program)

The "weekend" at Gordion, which is from Wednesday afternoon until Thursday, is a good time to venture beyond the dig house and explore other areas of Turkey. Last weekend, Cybele Tom and Jessica Pace, conservation interns at Sardis, an archaeological site in Southwest Turkey, joined Gordion team members on a visit to several Hittite sites located in Central Anatolia.

Yielding to a flock of geese on our way to Hattusa.

The trip began with a tour of the Gordion site, tomb, and museum, as well as Dua Tepe. After lunch at the Gordion dig house, we set out on a road trip to the city of Bogazkale, where we stayed at a charming hotel and enjoyed a lovely dinner in a restaurant with Ottoman style furnishings and a stone fireplace.

The Hittite sites and museums we visited include Hattusa, Yazilikaya, and Alacahoyuk. This group of students and recent graduates included three objects conservators, an architectural conservator, and an archaeologist, which made for very interesting, and interdisciplinary, conversation regarding the sites and museums.

Here are a few highlights from our trip:

Dua Tepe. A memorial dedicated to the Turkish War of Independence.
Reconstruction of mudbrick walls of Hattusa, capital of the Hittite Empire.
The amazing landscape that surrounds Hattusa.
The reliefs of Yazilikaya, a sacred site of the Hittites.

The gates of Alacahoyuk, a Hittite settlement.

Our adventure ended in Ankara, where the two groups separated and returned to their respective sites. We would like to thank our friends from Sardis for joining us on a wonderful trip!

Friday, July 1, 2011

Saf Su (Pure or Distilled Water) at Gordion

Our goal: obtaining saf su.

Distilled or deionized water is important in many treatments completed here at Gordion Excavations. Therefore, one of our first and top priorities is obtaining an appropriate source of water, which proved to be quite a challenge this season. We first attempted the deionizing columns left over from previous years, but after several rounds the conductivity of the resulting water was off the charts.

Discussing the deionizing column with a chemical salesman in Ankara.

During a trip to Ankara, we ventured on a mission to find a local source for purchasing deionizing columns. The set up for purchasing chemicals and supplies in Ankara is rather amusing. In one section of town, there are a few strip malls with stores that sell medical, laboratory, and chemical supplies. In many ways, the experience feels like purchasing a car. The chemical salespeople contemplated the column: they tapped it, shook it, sniffed it, then called in reinforcement, who also tapped it, shook it, and sniffed it. After several visits to different stores, many confused looks, and a few phone calls, we were unsuccessful in locating a column.

Angie sets up the still outside of the lab.

Defeated in our quest for a deionizing column, we set up the still back at the lab. Although the process is slow, after several days of running the still, we were able to obtain enough distilled water for the season. In case we run out, several small bottles of distilled water were purchased from a petrol station in Polatli, a nearby town.

Feeling sorry for the water-deprived objects conservators, Gordion
archaeologists purchased these cute little bottles of distilled water.

Perhaps next season will be more successful in the quest for purchasing a deionizing column in Turkey - a tip from an Ankara local suggested home improvement stores that may carry water filtration systems designed for the home.

With saf su in hand, Gordion objects conservators commenced with desalination and other treatments involving water.