Tuesday, July 13, 2010

Farewell, Gordion!

We're wrapping up the 2010 conservation season at Gordion, and saying goodbye to our friends and colleagues. It has been a busy and exciting season here, and we've had a great time. Thanks to everyone who has been reading the blog -- we've enjoyed all of the great feedback!

We'll be back next year, with more updates about life
 and conservation at Gordion! 

Sunday, July 11, 2010

Environmental Monitoring

Environmental monitoring has been an important aspect of the study and maintenance of the Midas Mound Tomb since the 1980s. The wooden tomb is potentially very susceptible to changes in the surrounding environment, and these conditions could be impacted by seasonal changes and tourists visiting the tomb. A thesis on the monitoring and conditions of the tomb was completed by Robyn Haynie, of the University College London, in 2009. The long-term monitoring has given us an excellent understanding of the seasonal changes that occur, and the overall environment of the tomb chamber.

Hygrothermographs were used in the past to monitor the conditions in the tomb chamber, but have now been replaced by electronic dataloggers. These dataloggers monitor the fluctuations in relative humidity and temperature, and are downloaded yearly to check the data. 

Richard Liebhart removes a datalogger placed 
inside the wooden tomb. 

The dataloggers have been placed in various areas around and within the tomb to compare micro-environments in the tomb and larger chamber. There are also tell-tale monitors to keep track of the expansion and contraction of the wooden logs making up the structure of the tomb. These indicate that while seasonal expansion of individual logs is taking place within the tomb, the structure is stable overall.

Emily and Elizabeth change the batteries on the dataloggers.

As the dataloggers are only checked once a year, it is important to ensure that they function properly for the duration of the year. We change the batteries each time, just to be sure that this is the case.  

 Jessie analyzes the downloaded data.

The information is dowloaded, and compared with information from previous years. This enables us to ensure that the conditions are behaving as expected, and that major changes to the environment have not occurred.   

Sunday, July 4, 2010

Treating Bronze Objects

Many bronzes have been recovered in excavations at Gordion. The large amount of bronze material, and the moisture in the burial and storage environments result in corrosion on many of these objects. The application of Benzotriazole (BTA), a corrosion inhibitor, is a common treatment for these materials. This is a less invasive treatment options than those often employed in the past, such as chemical stripping.

The objects requiring treatment were selected in the course of our condition survey because of visible active corrosion. The presence of active corrosion often indicates that environmental conditions are affecting the stability of the objects. Past research has been done at Gordion to examine the conditions within the display cases, including Oddy tests and monitoring with dataloggers. The results of this research indicate that these objects are displayed in relatively stable conditions. It now seems likely that the corrosion could be caused by chemical reactions from previous treatments. There are not written records about many of the early conservation treatments, but personal recollections of past practices confirm that this is a possibility.

The standard procedure for treating bronze objects at Gordion follows these general procedures:

If necessary, objects are desalinated to remove soluble salts and 
chemical residues from previous treatments.  

The objects are mechanically cleaned, using a glass bristle brush and
scalpel, and then brushed with ethanol. 

They are then degreased with acetone and placed into a solution of BTA in 
ethanol. The objects are placed into a vacuum chamber to help increase
 the penetration of the solution.

After removal from this chamber, the objects are coated with dilute B-44 acrylic resin. Here we are coating the larger bronze object after treatment with BTA by filling a plastic bag with B-44 solution. This allows us to evenly coat the surface using a minimal amount of resin.

Recently there has been discussion among conservators about the appropriate procedures and effectiveness of BTA as a treatment for bronze corrosion. Julie Unruh, Gordion conservator-at-large, has been actively researching these issues. Questions include the effectiveness of BTA and AMT (another corrosion inhibitor) in combination, the appropriate length of time for BTA submersion, the efficacy of the vacuum chamber, and the possible substitution of corrosion inhibitors with desiccation and environmental controls. If anyone wants to share their knowledge of the effectiveness of these treatments, we would be very happy to hear your thoughts. 

Friday, July 2, 2010

Examination of Archaeological Glass

Researcher Janet Jones has been working on the identification and classification of the glass assemblage found at Gordion. Among the many examples of glass from the site, there are several examples of relatively complete glass vessels. We spent a day helping her with a technical examination of some of the Roman and Hellenistic mosaic glass examples. One of Janet's goals was to examine the patterns and colorants within the glass to get a better sense of their construction. This is useful when determining whether the pieces are all from a single vessel or if there are actually fragments from multiple objects.

The mosaic fragments in their storage housing

One of the difficulties of identifying glass colors is finding a suitable light source for viewing the object.  To facilitate our examination, we set up a temporary light-box. This was made by supporting the microscope on a glass plate, suspended over a lamp in a plastic crate. This created a way to view the piece in transmitted light while under magnification.

Jessie examines the glass on our improvised light table

The surface of the fragments are heavily weathered, obscuring the original colors of the glass. In some areas, we mechanically removed small portions of the weathering layer to determine if the colors of the weathering layers correspond to the colors of the glass underneath. The appearance of the weathering layers on separate pieces did not always correspond, indicating that fragments might have been subject to different burial environments.  In our investigation, we were able to determine that several of the fragments share a repeating pattern of blue, yellow, and aquamarine, suggesting that they are from the same vessel.

The small fragment at the bottom reveals gold foil sandwiched 
between two colorless layers.

One fragment appears to contain gold sandwiched between layers of colorless glass, which is a known technique in ancient glass manufacture. This bowl is Roman and dates to the first half of the 1st century C.E. The gold was observed several seasons ago by a different group of conservators and Janet was interested in looking further at the other fragments to see if more areas with gold could be identified. We weren't able to identify other areas of gold foil, but this would be a promising area for materials analysis of these glass pieces.

The short strip mosaic fragment

While the construction of the majority of the pieces is similar, there are several pieces made with a short strip technique. While stored together, these mosaic pieces appear to come from an entirely separate vessel and likely date to the Hellenistic period. Stylistic features can be useful in the dating and classification of glass, and the technical study of these pieces will assist Janet in her analysis and interpretation of the Gordion glass assemblage. 

Wednesday, June 30, 2010

Animals of Yassıhöyük

One of our major sources of amusement for the staff here at Gordion is animal watching. Here are some animals we have encountered in our daily travels to and from the museum.

A local turkey, known as a hindi in Turkish. This one is unsuccessfully trying to camouflage itself in the grass.  

One of the owls that lives at the dig house. 
Photo courtesy of Andrew Goldman.

One of our favorites! A hoopoe (ibibik in Turkish) in the yard of the dig house. Photo courtesy of Andrew Goldman. 

The local flock of sheep that parades past the house every day at cocktail hour. The donkey on the left diligently leads the sheep around the village. 

A friendly tortoise.

A hedgehog that hangs out at the museum.

Tuesday, June 29, 2010

Altar Update

The cleaning of the two marble altars mentioned in a previous post is progressing. The first altar, which had surface accretions removed from its inscription area in earlier seasons, has been cleaned further by Jessie this season. The figure of winged victory is now visible, revealing a surprising level of detail.

Winged victory, with much of the surface deposits removed.

These altars are of great interest to the archaeologists at Gordion because they provide a record of the Roman legions that were present at the site. This altar differs from the first altar in that the inscription was scraped out, perhaps due to a change in political power. Under the practice called damnatio memoriae, the Roman Emperor Caracalla had the memory of his brother Publius Septimus Geta expunged after Caracalla seized power and killed his brother. The cleaning of the inscription on the second altar is over 50% complete. Microchemical spot testing was performed in previous seasons to identify the composition of the deposits, and identified carbonates in the material. We experimented with different methods, but found that mechanical cleaning with scalpels and small chisels was the most effective. 

Detail of the surface deposits on the top of the altar.

Emily and Elizabeth mechanically reduce the deposits. 

To clarify inscriptions that are difficult to read, epigraphers sometimes take relief impressions with paper pulp. These impressions, called squeezes, are created by tamping down wet pulp to the stone surface using a brush. When the squeeze has dried, it may be removed from the stone and will reveal a 3-D relief of the inscription. We attempted to make a squeeze on part of the erased inscription with toilet paper and water, beating individual sheets into the surface with a brush and repeating the process with multiple layers. While our squeeze was effective in capturing the topography of the erased area, the portion of the inscription that we examined was so thoroughly defaced that it was not legible. As more of the inscription surface is revealed we will continue to study the lettering.

Elizabeth and Emily prepare a toilet paper squeeze of one portion 
of the inscription.

Monday, June 28, 2010

Cleaning the World's Oldest Standing Wooden Building

We have been working with archaeologist Richard Liebhart on the wooden tomb located within the Midas mound. This tomb is the oldest standing wooden structure in the world (c. 700 B.C.).

A view of the Midas Tumulus, which houses the wooden tomb.

The tomb structure is formed by four walls of solid tree trunks laid horizontally and stacked, with a roof of tree trunks laid across the top. The body of an older male was found in the tomb with textiles, wooden furniture, and groups of bronze vessels and pottery containing food residues that have been the subject of extensive analysis. More information about the contents of the tomb and previous research about the materials can be found here. Long thought to be the remains of King Midas, current research now suggests that the body is slightly older than Midas and may be his father. The contents of the tomb were removed during the excavation, so current conservation work on the tomb is centered around the cleaning and maintenance of the wooden structure.

Richard Liebhart surveys the roof of the tomb. The wood seen on the left is heavily 
coated in dust, debris and concrete. 

A concrete support structure was built around the tomb in the 1960's to support the weight of the massive mound surrounding the tomb chamber. Though it seems to be working successfully, there are many places where the concrete dripped onto the wood during installation. Our cleaning has involved gently brushing the wood and vacuuming the massive quantity of dirt on the surface to reveal the concrete spots underneath. We are removing the concrete from the wood mechanically with small tools and documenting the appearance of the wood before and after cleaning.

Elizabeth documents the condition of the wood before cleaning.

Cleaning is a team effort! Jessie holds the light source, while Emily brushes 
the surface of the wood and Özge holds the vacuum. 

This is no ordinary cleaning project for us, as working inside the tomb presents the extra challenge of working in spaces with limited access. This season we are working on an area of the roof, requiring us to climb up an artfully rigged frame structure and conquer any fear of heights as we work several meters off of the ground. Turkish student Özge Sırma has been assisting us with this project, along with other work going on in the lab.

Moving around the top of the tomb is a complicated endeavor. Don't look down!

In addition to cleaning, environmental monitoring is a key part of our work in the tomb. Dataloggers recording fluctuations in temperature and relative humidity are installed in several places throughout the tomb. Since wood is a material that undergoes substantial dimensional change as a result of variations in relative humidity, it is critical that the environment remains stable to ensure the structural stability of the tomb. The perimeter of the tomb is accessible to visitors, who alter the environment of closed spaces by adding heat and moisture. Human impact is a major threat to heritage sites, but so far there does not appear to be a substantial impact on the environmental conditions of the Midas Tumulus from visitors.

Sunday, June 27, 2010

Condition Survey at the Gordion Site Museum

Nearly all of the excavated materials from Gordion have remained in Turkey. Many of the most significant finds are now on display in the Museum of Anatolian Civilizations in Ankara, but the majority of the material remains in Yassihoyuk. The Gordion Museum displays many of the finds from tumulus mounds, the citadel mound, and the surrounding community. For the conservation staff at Gordion, the maintenance of the museum collections is a priority.

The new wing of the Gordion Museum. 

There is an annual condition survey of the objects on display within the museum. In this survey we noted any change in the condition of objects over the course of the year. We also noted issues with object mounts, cases, and the gallery environment. Information was also downloaded from dataloggers installed in several of the cases, which record fluctuations in temperature and humidity in the museum.   

Emily fills out the survey form, recording the condition of 
bronzes in the old wing of the Gordion museum.

The museum displays a wide range of material types, including ceramics, metals, ivory, glass, stone, and human remains. Common problems within the collection include salt efflorescence on the ceramics and corrosion of the metal objects. As time allows, we also revisit previous treatments, including failing adhesives and fills that can be improved.

Common problems in the collection include failure of adhesive from previous repairs (above), and corrosion of bronze objects (below). 

As a result of our survey, we have identified several objects in need of treatment. These include possible chloride corrosion on bronzes, failing adhesive joins on several iron objects, and ceramics with severe salt efflorescence. We will spend the remainder of our time here treating these objects, and will share the treatments as they progress.

Jessie removes an object from the display case, and places it into a 
makeshift tray for safe transit back to the lab.

Saturday, June 26, 2010

Conservation in the Field

Being in the field poses many challenges for the conservator. Routine materials may not be available, environmental conditions may be radically different than museum standards, and time is limited to several weeks a year. 

We've learned a technique for deionizing water, which is necessary in many cases for the desalination of pottery and other conservation treatments. There are large amounts of salts in the burial environment, which solubilize and migrate into the objects. With changes in relative humidity after excavation, these salts can effloresce on the surface of an object and potentially cause considerable damage. Desalinating removes these salts from the fabric of the object and at Gordion is carried out on ceramics and metals.

In order to carry out the desalination, a source of deionized water is needed. The tap water here has high conductivity, and must be treated to remove minerals prior to use in desalination. This is done using a deionizing column onsite. 

Emily pours water from the tap into the deionizing setup.
Water is then forced through the deionizing column shown above. 

Elizabeth checks the conductivity of the water after deionization. 

Obtaining supplies can also be a challenge and it is often necessary to find creative materials for use in conservation treatments. We ventured out with Jessie in Ankara to find acetone when we first arrived in Turkey. It was an interesting opportunity to learn about the differences of buying supplies in a foreign country and the ways in which chemical suppliers and safety standards might vary. 

Not on the the list, but tempting. 

Adapting to life in rural Turkey is another interesting part of working in the field. We have been working on our Turkish, and enjoying the local cuisine. One of the first phrases we've learned in Turkish is "elektrik yok", which means no electricity. Power outages are a daily occurrence here, but everyone makes the best of it. A popular way to spend the time is in the newly fabricated "Gordirondack" chairs, made for us by John Hinchman and friends. 


Friday, June 25, 2010

The Delights of Conservation

Here at Gordion, we have a busy schedule, which includes breakfast at the early hour of 5 o'clock. By second breakfast at 9, everyone is ready for a break. Luckily Turkey is home to an amazing array of cookies, and second breakfast is filled with a constantly changing selection of not-so-healthy choices to accompany our tea.

A selection of the cookies of Turkey:

Anonymous Tea Biscuit



The Perils of Conservation

Emily wins the prize this week for most unusual bug bite. 

...but don't worry, Benadryl is working its magic. 

Wednesday, June 23, 2010

Students at Gordion

2010 Kress interns Emily Hamilton and Elizabeth Drolet getting a tour of the construction of the Midas tomb chamber (the world's oldest standing wooden building) from Dr. Richard Liebhart.

Since the beginning of the Gordion Objects Conservation Program in 1988, training has been a major focus of the program. The generous support of the Kress Foundation has funded numerous conservation interns, allowing them to learn more about how burial and excavation affect the artifacts that end up in collections. It gives students a much deeper understanding of why archaeological objects are deteriorated and damaged and helps them to make better decisions about how to care for them. Working here also gives students an opportunity to more deeply understand how archaeologists study artifacts, and what can be learned from them. It also gives students an opportunity to see how archaeological sites and excavations affect the local community. Here’s a list of some of the things that students at Gordion get to do:

  • They work on material excavated over the past 60 years to stabilize, and restore artifacts.
  • When excavations are taking place they work on material recovered during the season to clean, stabilize and sometimes reconstruct objects.
  • They survey collections on exhibit at the Gordion Museum to look for new damage, and also do projects to improve the aesthetics of old restorations
  • They work on projects designed to monitor and ensure the safety of collections not on display.
  • They are introduced to the long-term monitoring of the MM (Midas Mound) tomb chamber and help to clean it of debris left over the decades of exposure.
  • They work with researchers to stabilize, clean and restore artifacts that are being studied for publication
  • They interact with many, many different experts in archaeology, architectural conservation, geology, cultural anthropology and other fields who are all here working and living together.
  • They meet Turkish colleagues in cultural heritage, particularly our friends and colleagues from the Anatolian Civilizations Museum in Ankara
  • They learn how to do good conservation in less than ideal circumstances
Below is a list of the conservators who have worked as part of the Objects Conservation Program:
Sarah Barack
Tom Braun
Angie Chang
Esther Chao
Dena Cirpili
Matt Crawford
Julia Day
Guldem Derinengin
Elizabeth Drolet
Angie Elliott (Head of Objects Conservation 2006 – present)
Emily Hamilton
Cricket Harbeck (Head of Objects Conservation 2000-2005)
Robyn Haynie
Lauren Horelick
Tara Hornung
Jessie Johnson (Head of Objects Conservation 1991-2000)
Hüsnü Kayisbudak
Steve Koob (Head of Objects Conservation, 1988-1990)
Yunhui Mao
Ariel O’Connor
Nathan Otterson
Susan Russick
Ellen Salzman Chase
Eva Shipp
Brenda Smith
Julie Unruh
Özge Üstün
Chris White

Tuesday, June 22, 2010

The World's Oldest Pebble Mosaic

One of the projects we're currently working on is the cleaning of a large pebble mosaic, that dates to the 9th century BC.

The mosaic was found intact in Megaron 2, during excavations in 1956. The mosaic was lifted from the original location, to be stored off-site. After lifting, the mosaic was backed with concrete, and has been displayed at the Gordion site museum since the 1980s. It is currently displayed in a sunken area with a protective roof, but is still exposed to birds, dust, rain and other environmental factors.

Current work is being done by a team from the Historic Preservation department at the University of Pennsylvania, including professor Frank Matero and graduate student Tiffin Thompson. The current work, funded by the Kaplan Foundation, is part of a three-year conservation plan for the mosaic. The first step is the documentation and condition assessment of the mosaic, to determine overall stability and deterioration of the tiles. The team will then compare the current placement of the tiles with archival images and field notes. This will enable them to assess how closely the current position of each tile matches the original layout. In the final phase of the project, the tiles will be stabilized and excess concrete cleaned from the surface. The team also plans to examine the condition of a similarly dated mosaic, still in situ within the main excavation site, to better understand the deterioration and fully document the mosaics found at the site of Gordion.
Tiffin works on a condition survey of the tiles.

Elizabeth cleans one of the tiles using a brush and vacuum.