Plaster Master!

Susanne Grieve

Now that we are in our third week, the lab has been in full swing! We have several people working with the project including specialists in botanical materials, faunal remains, pottery, conservation, architecture, bioarchaeology, and geoarchaeology. In addition to…ahem…interesting discussions on bone decomposition, there is dialogue on the interdisciplinary nature of the project. As an archaeological conservator on site, my role is to stabilize and preserve the artifacts that have been excavated from the tombs and domestic areas of the North Ridge.

Most of the excitement in conservation comes the fact that you never know what will come across your bench from the day’s excavations and some days you may be doing the excavating! Because of the site conditions, many of the metal materials are covered in sediment and a compact material we call concretion. These can mask any surface details on the object and it isn’t until they are cleaned and stabilized that you can read inscriptions or see details. For example, some of the coins that we have found so far are heavily concreted, but after conservation, we can identify a date range for that particular locus. Coins always produce the best reactions, but my favorite material to treat so far has been several fragments of plaster.

As you can imagine, even when it is decorating modern walls, it is a fragile material. Combine this with almost 2,000 years of burial and it becomes really fragile! Since our fragments are disarticulated and are found separated from the wall we can relocate them to a more controlled environment such as the lab to treat them. But, transportation of objects has the highest risk of damage so to prevent anything from affecting their fragile painted surfaces, we placed them in buckets and covered them with sifted soil from the trench. This ensured that there was minimal movement of the object and that nothing would abrade the surface of the plaster. (Side note: Conservators often deal with painted surfaces that are still intact and use a technique called “facing” if the surface has to be removed from its in situ location). Once back in the lab, I could take a closer look at the extent of deterioration and determine the best approach to treatment.

In Action A

In Action B

As I examine the object, I like to envision what the room would have looked like. Many of the fragments contain layers of paint in red, black, green, and yellow, but with all of the surface dirt adhering to the paint, it is hard to interpret the designs and colors. My first step is to clean the surface of the plaster in preparation for stabilization techniques and to determine how loose the surface is. This proved very difficult with these pieces, as the paint was loosely adhered. In the end, I had to clean the fragments with very light brushing using a soft brush on unpainted areas and a light flow of air over the painted areas. This worked well to remove the lightly adhered sediment, but left the painted areas in tact.

This particular plaster section also had some fascinating construction details:

Plaster Layers Obverse

Reverse AT With Terminology

Since the paint was so fragile, it was decided that the next step should be to consolidate it before any losses could take place. Luckily this step also brought out the beautiful paint colors and allowed us to see patterns that were nearly invisible before. The end result? A stable plaster that can now be used for study!

Obverse BT Low Res

Before Treatment

After Treatment

After Treatment

Before Treatment

Before Treatment

After Treatment

After Treatment

While it doesn’t produce the wow factor of coins, it is such a great feeling knowing that you helped stabilize a very fragile object. Next up on the bench: clay figurines!

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