Sunday, June 26, 2011

Soccer and Mulberries in Yassihoyuk

The Yassihoyuk mosque.

One afternoon, during our walk to the museum, we passed by the Yassihoyuk mosque. The courtyard of the mosque was filled with children from the village. We stopped to say hello and practice our Turkish. I do believe one boy said "Your Turkish is bad." Children are so honest.

Soccer in the mosque courtyard.

Angie joins the soccer game.

The children began a game of soccer, and we decided to sit in the shade of the courtyard and observe. Angie couldn't resist joining the game. A couple of the kids were standing on the wall, picking some fruit off a nearby tree. We stopped to get a closer look, and saw some white mulberries ripe for the picking! While we tried to figure out which berries were best to eat, an older village woman came out help us. The next 15 minutes were spent eating handfuls of delicious, juicy mulberries she picked for us. What a wonderful afternoon break, before heading back to work at the lab!

Delicious mulberries.

Saturday, June 25, 2011

Slumping Ceramics

Gordion archaeologists are not excavating this season which means that we can devote more of our time to taking care of the collection. Our job as conservators does not end once objects are cleaned and stabilized after they are excavated. A continuing challenge is our slumping ceramics. Most of our pots, plates, and other ceramic vessels were carefully assembled from many fragments because they rarely come out of the ground unbroken. In the earlier days of Gordion, a PVA resin adhesive was used to glue the ceramics back together. Over time, these earlier ceramics have started to sag, slump, and come apart.

This Phrygian jug, treated in 2009, slumped over the course of one year
and could no longer stand on its own.

The adhesive slowly starts to soften and the joins begin to pull apart exposing strings of adhesive. One reason this happens is that the adhesive's glass transition temperature, or Tg, is too low. The Tg refers to the temperature where a material like an adhesive goes from a hard, brittle material to a much softer, rubber-like material. Our storage areas have no air conditioning and the temperatures can get pretty hot! The older adhesive used here has a Tg that is in the same range as the high temperatures in storage so the adhesive starts to soften and pull apart. 

Adhesive strings in joins indicate that the vessel is unstable
and could begin to slump and fall apart. 

We keep an eye on our ceramics each year to determine if there are any emergency cases that should be treated. The only solution is to remove all of the adhesive and put them back together again with an adhesive that has a higher glass transition temperature. 

A collapsed pot that is being treated this year. 

Friday, June 24, 2011

An Update on Salts

Here are some microscopic images of salts present on a ceramic from a previous post.

Microscopic image of hair-like crystals on the blue-colored fills.

The ceramic surface shows granular salt crystals.

We are currently in the process of preparing the ceramic for desalination, including consolidation of flaking surfaces and removal of old plaster fills. But before we desalinate, we have to find a good water source, which is a challenge out in the field. Stay tuned for our adventures hunting down an appropriate water source!

Tuesday, June 21, 2011

Unseasonal Rain and Its Effects on Cleaning Stone Altars

The normal field season at Gordion experiences very warm weather. However, this summer so far has been unusually cold and wet; in fact, it rained nearly every day for a week!

We enjoy the amazing cloud formations on a walk back to the dig house.
Muddy roads after a sudden downpour of rain.

Although the rain allows for enjoyment of beautiful clouds like the ones seen above, our walks to the site museum were rather muddy. Cars must also contend with the downpour of rain; the architectural conservation team was stranded on site when their vehicle got stuck in the mud. Kenneth Sams, Director of Gordion Excavations, had so much mud stuck in his tires, they caught on fire while he was driving!

However, there are some surprising benefits to the rain. In previous seasons, the deposits on two stone altars were particularly hard and difficult to remove. The elevated humidity from the recent rains has softened the deposits, and some areas are now flaking off rather easily. We plan to take advantage of the situation and remove the deposits while they are still soft from the rains. More stubborn areas will first be softened with a poultice and gently removed with a scalpel or chisel. This is a particularly useful approach for deposit layers closest to the stone.

A poultice, comprised of paper towels soaked in water, was applied to soften the deposits.

Last season, the conservation team applied a toilet paper squeeze to study the defaced inscriptions. Unfortunately, the inscription was still not legible, perhaps due to fine layers of dirt. Hopefully, after further cleaning, we will have more luck this season!

Monday, June 20, 2011

Visiting the Gordion Frescos

Our conservation season got off to a great start this week with a trip to the Museum of Anatolian Civilizations. This museum, housed in an historic bazaar building in Ankara, contains some of the best finds from the area's excavations including our own Gordion wooden furniture. Research still continues behind the scenes at the museum. Dr. Susanne Berndt-Ersöz has been researching and reassembling the Gordion fresco fragments excavated in the 1950s. These frescos were discovered in a small, partly subterranean building known as the Painted House and have been dated to 500-490 BCE. 

Reassembled fragments
1957 watercolor reconstruction by Piet de Jong

Most of the fragments are currently housed in small, acidic paper boxes. These boxes are harmful to the fragments and do not allow the reassembled pieces to be stored together. Elizabeth Drolet, one of our 2010 interns, worked on a rehousing plan over the past year. We went to evaluate the fresco's condition and discuss the plan with Dr. Berndt-Ersöz. We were excited to see these much talked about frescos in person!

Latif Özen, our friend and colleague at the museum, also took us on a tour to see the museum's conservation laboratory. There are a dozen or more conservators that work in the laboratory and almost half of the them of scientists. Latif, a chemical engineer, has been analyzing the fresco pigments using their new portable x-ray fluorescence spectrometer. This instrument is non-destructive and can determine what elements are present without taking a sample. We hope to hear more about the analysis in the near future and will keep you posted!

Latif and Lily in the museum's conservation laboratory

2011 Condition Survey: Salts

We start the season at Gordion with a condition survey of the museum collection. A survey is an overview of the collection, where we quickly examine each object on display and note condition issues. The survey is completed on a yearly basis, allowing for comparison of survey results with previous years so that objects in need of attention can be prioritized.

One of the condition issues we have encountered is the presence of salts, a common problem with some archaeological materials, particularly ceramics. When hearing a conservator talk about salts, the white crystalline material found in the common kitchen, possibly occupying a shaker marked with an "S" on your dining room table, might come to mind. Actually, this is not too far off the mark, because table salt, aka sodium chloride, is simply a purified form of one type of salt.

It may sound odd that salts are present in archaeological objects, but it is a fairly common occurrence, since salts are present in burial dirt. If they are not removed, then salts may either obscure the surface or cause damage to an object.

During our survey, we discovered salts present on this ceramic:

The salts are the powdery white crystals seen here on the rim.
The salts have caused some damage to the surface.

A particularly interesting, and unusual, discovery is the blue area in the above green box, which is located in a fill rather than the original ceramic. Examination of this strange blue area revealed hair-like salt crystals that are not found on the other, non-blue fill material, and is different in shape from the other salt crystals present on the ceramic.

The blue area of the fill contains hair-like crystals that are
different from other salt crystals found on the ceramic.

The objects conservation team plans on treating this ceramic to remove the salts, via a process called desalination. Samples of this strange blue material may be removed for analysis back in the US, at one of the conservator's home laboratories. The analysis may shed light on why and how these crystals were formed on the fill material. Stay tuned for an update on this treatment!

Sunday, June 12, 2011

We're back: The 2011 Conservation Season Begins!

The Gordion Objects Conservation Program is gearing up for another season as the conservation team begins arriving this week. Our season began June 11 and will go through July 13. Conservators Angie Elliott and Jessie Johnson will switch off in the middle of the season and graduate student Lily Doan ('12) from the UCLA/Getty Program in Archaeological and Ethnographic Conservation will be around the entire season. Angie has begun to set up the conservation lab at the Gordion Museum so we will soon have more to tell you about our season's projects. In the meantime...

Our first challenge has been the thickest vegetation that we've ever seen at the site. The paths through the fields are barely visible and our shoes, socks, and pants are being attacked by painfully prickly hitchhikers. We hope to flatten the paths as we go to the museum more often. Our temporary solution has been to wear flip flops because they have nothing to grab!

It takes about 15 minutes to walk to the museum from the dig house.
The path through the fields is barely visible.   

The culprit. 

The painful result.