Putting the finishing touches on the shabti box

I have put a lot of work into our troubled shabti box, including investigating and analyzing the varnish (more on the analysis in an upcoming post), doing some pretty cool imaging, and consolidating all flaking and unstable varnish and paint with methylcellulose. After consolidation of the surfaces, the box does not look much different than it did when I started the treatment (and this is a good thing). As a reminder, here is an image of the front of the box before treatment:

shabti box frontAt this point, I could call the treatment done, or take it a step further, by filling in some of the losses of the painted surface, which appear bright white since those losses expose the gesso below. After consulting with Dr. Jen Wegner in the Egyptian Section and with Lynn Grant, the head of our department, I decided to fill in some of the larger losses which really make it difficult to appreciate the object and “read” the designs. I have even heard some visitors refer to the box as “that badly damaged piece of wood”, and that is not what we want people to be thinking when they eventually see this on display. While I know I can never return the box to its original condition, I can reduce the appearance of some of the damage. But how to fill the losses on such a fragile surface, in a way that will be reversible/retreatable?

After some hemming and hawing and some failed tests, I ultimately decided to fill the losses by first placing a small piece of Japanese tissue paper into the loss, then applying a tinted fill mixture over the paper. I did this by doing the following:

1. I took a quick snapshot of the surface I was about to work on. I then downloaded the image and copied it into a Word document. Using the scale in Word, I was able to resize the photograph in order to print it approximately true to size, and then I printed the image in black and white. This took no more than 5 minutes.

2. I placed a piece of Mylar over the B&W print-out and traced the losses I wanted to fill with a black marker.

L-55-23A_template2

B&W image with Mylar template moved off to the right side

3. After trimming the Mylar around one of the tracings, I taped it to a piece of Japanese tissue paper with a small piece of blue tape.

L-55-23A_template34. I cut out the Japanese tissue paper and adhered it into the loss on the shabti box with a small amount of 5% methylcellulose.

5. I then applied a fill mixture over the Japanese tissue paper. The fill mixture is made of 5% methylcellulose, glass microballoons, and powdered pigment.

Fill mixture (in the jar and on the spatula)

Fill mixture (in the jar and on the spatula)

This may sound tedious, but the whole process works very smoothly and relatively quickly. It also minimizes the amount of time I need to spend touching the object and therefore minimizes damage that might be caused by touching the very fragile surface.

I’m not finished, but so far I’m pretty happy with how the front of the box is looking:

L-55-23A_dt01_compressed

Front view, during filling

It’s subtle, but to see the difference that filling makes, here are views before and after, side-by-side:

Picture1

Before treatment (left) and during treatment (right)

The only problem is, I feel like I’ve opened a can of worms. There are so many losses and I am not going to fill them all, but as soon as the larger losses are filled, I start seeing all of the small ones! I think it’s looking better though and I will get some feedback from my colleagues before proceeding further.

 

Investigating the shabti box coating

Last month, I wrote about a new challenge in the lab, otherwise known as this shabti box and its associated shabtis:

front compressedAt first the box came into the lab with 3 shabtis, and then we found that there were 3 more in storage that may belong with the box as well. 4 of the shabtis are very similar in appearance whereas the other 2 are slightly different, so they may actually not be associated after all. Can you spot the 2 different shabtis?

2 of these things are not like the others...

2 of these things are not like the others…

All of these objects are made of wood, gesso, and paint. And as you can see, all of them have an orange-yellow coating on their surfaces. In my last post I posed the questions “what is this coating?” “is it an original varnish or is it a later restoration?”. My initial guesses were that it is either an original pistacia resin varnish, a later cellulose nitrate (or other old restoration adhesive) coating, or a combination of the two.

Well, there are several things we can do to try to answer these questions and to narrow down the possibilities. One of the first things I did was to look at these objects very carefully using our binocular microscope. I could see that the coating was applied unevenly, especially on the box, and that it is actively cracking and flaking. Another thing that I noticed was that there are areas on the box where the paint is lost and where the coating extends over the loss onto the gesso below.

A detail shot of one side of the shabti box - the yellow arrows are indicating areas where the coating extends over an area of paint loss onto the gesso.

A detail shot of one side of the shabti box – the yellow arrows are indicating where the coating extends over areas of paint loss onto the gesso.

Usually, this would indicate that the coating was applied after the damage occurred (so sometime after excavation, either in the field or soon after coming to the museum). So this is one clue, but doesn’t really answer my questions.

Next, I examined the shabti figures under ultraviolet (UV) light. In conservation we routinely use UV examination to characterize materials and to distinguish old restoration materials from original materials – for instance, shellac, used historically to repair objects, exhibits a characteristic bright orange fluorescence under UV. (For a great explanation of UV, along with some interesting images, check out this post on UV examination by my colleague Allison Lewis, conservator at UC Berkeley’s Phoebe A. Hearst Museum of Anthropology.)

The coating on the box and the shabtis has a yellow-orange appearance under UV – but not the bright orange that we expect to see from shellac.

shabti UV

4 shabti figures under UV light

So UV examination was helpful (it eliminated shellac as a possibility) but didn’t answer my questions either.

Next, I did a microchemical spot test on a couple of the previously detached flakes of the coating. We’ve used spot-testing before in the lab – the last time I wrote about it was in reference to the mystery fibers on Tawahibre’s coffin. In this case, I carried out a spot test for nitrates using diphenylamine (according to instructions in Material Characterization Tests for Objects of Art and Archaeology). Using this test, a sample containing nitrates will turn blue once a solution of diphenylamine/sulfuric acid is added. Below you can see the result of the test on one of the coating flakes from the shabti box (left) and the test on a control sample of cellulose nitrate adhesive (right).

Left: coating sample from the box after spot test (negative result) Right: control cellulose nitrate adhesive after spot test (positive result)

Left: coating sample from the box after spot test (negative result) Right: cellulose nitrate control after spot test (positive result)

Based on these results, it seems that the coating does not contain cellulose nitrate. This does not mean that the coating does not contain another recently-added adhesive. We have a few other ways of narrowing down the possibilities even further, and I will write about our continued work on this in my next post.