Consolidating and reconstructing glass objects

* A new post from former Artifact Lab graduate intern Laura Galicier, contributing from a distance in Paris!

Reconstruction of a fish-shaped vessel from ancient Afghanistan (picture from a video of the British Museum, that can be viewed at https://www.britishmuseum.org/channel/exhibitions/2011/afghanistan/video_glass_blowing.aspx

Reconstruction of a fish-shaped vessel from ancient Afghanistan
- picture from a video on the British Museum website, that can be viewed by  following this link

Two glass objects from Cyprus were previously introduced to you. After an initial examination, several treatment steps were decided.

First, the surface showed evidence of delamination and was slightly flaking. We chose to consolidate the surface because if this destructive process went on it could lead to the complete loss of the object. An acrylic resin (Paraloid B72, that you’re now pretty familiar with) in acetone was chosen to do this light stabilization.

Then, we tried to see if the pieces from each object could be built up. We found that while the jug (n.63-1-196) would be able to reconstructed, the fragments of the bowl (n.63-200) didn’t fit together.

On the right: the glass jug    On the left: the glass bowl

The glass jug                                                                         The glass bowl

So the building work for the jug began! We had to find where every fragment was supposed to go. If you read our blogpost about the Egyptian Demotic jar, you’ll realize that building up a glass object is very different. Of course, the size of these glass fragments is considerably smaller than the jar fragments. Besides, the edges of a ceramic are irregular, which can help with reassembly, whereas the edges of glass are smooth.

Glass fragments glued together

Glass fragments glued together

In terms of thickness, a glass object can be very irregular, especially after deterioration, such as delamination of the surface. Generally, you hope that two fragments of similar thickness belong to the same area of the object, but with glass, delamination makes it possible for two fragments of very different thickness to fit together. Moreover, compared to ceramic, glass fragments have a very different way to adjust to each other.

Despite these differences, the methodology to reconstruct glass and ceramic has some similarities: it is necessary to map out the joins so as to know precisely where each fragment goes.

After a bit of work the fragments were put in the order to be joined.

The fragments arranged in the right order

The fragments arranged in the right order

Then, the fragments were temporarily reconstructed using scotch tape. Taping the joins clarifies where each fragment goes and exactly in which order to build them up. This order isn’t always the most obvious but if it isn’t respected, a fragment could prevent another one to fit.

The fragments were built together with scotch tape.

The fragments were built together with scotch tape.

Then, the scotch tape was removed and the fragments were glued with an adhesive (Paraloid B72). Three groups of fragments were reconstructed: fragments of the top, fragments of the bottom and a few fragments that should be placed in-between. The in-between fragments couldn’t be glued to the top or to the bottom because there’s a wide gap between them and the other fragments. This is why it was necessary to make fills so as to support these before going any further.

The three groups of fragments reconstructed and glued together.

The three groups of fragments reconstructed and glued together.

The fills will be explained in a post to come!

 

Back together again

Okay, I promised to write about the shabti box investigation in my next post, but before I do that, I have to share something exciting with all of you:

PUM I, our Third Intermediate Period mummy who was autopsied back in 1972, is back together again!

PUM I, before treatment in his coffin

PUM I, before treatment in his coffin

When he came into the lab, we didn’t realize how much he had been cut apart, and the extent to which his remains and linen wrappings had deteriorated. We have spent a lot of time examining this mummy, researching his history including his autopsy, cleaning the deteriorated linen and human remains, identifying and inventorying the remains (thanks to Penn undergraduate Christine Lugrine), and conserving the linen wrappings.

The conservation work on his remains is nearly complete, and he will soon leave the Artifact Lab. Come visit the lab for one last glimpse, and check out the before and after photos below.

Overall shot of PUM I before and after conservation

Overall shot of PUM I before and after conservation

View from the top of PUM I (with head removed) before and after conservation

View from the top of PUM I, with head removed, before conservation (with remains in plastic bag inside the chest cavity) and after conservation (with Ethafoam supports filling out chest cavity)

Inside the chest cavity of PUM I before and after conservation

Inside the chest cavity of PUM I before and after conservation (with Ethafoam supports)

Another view looking inside PUM I before and after conservation

Another view looking inside PUM I before and after conservation (with Ethafoam supports)

Remains removed during autopsy before and after conservation/re-housing

Remains removed during autopsy before and after conservation/re-housing

 

 

The jar is gone !

Example of an Egyptian jar, complete (XVIIIth Dynasty).

Example of an Egyptian jar, complete (XVIIIth Dynasty).

After making some fills on the Egyptian demotic jar, two other steps remained to complete the treatment.

First: painting the fills. The goal is to tone the fills with a color matching the general shade of the ceramic, so as it doesn’t catch your eye when you’re looking at it from a few feet away. It has to be clearly distinguishable if you get a closer look.

Here is the result:

Untitled-2 Let’s have a closer view:

Untitled-3

Untitled-4

View of the 4 areas of the jar that were filled and toned.

Second step: making a storage box. The basic rules about storage-making are quite simple. The materials used to make the storage must be chemically neutral towards the object and their ageing must not threaten its condition. For example, some materials can deteriorate in a short-term time period and cause chemical reactions with the artifact they are supposed to protect, causing alterations.  That’s why conservators use materials that were approved by testing them, like submitting them to specific temperature or humidity settings. More details about storage materials can be found following this link.

To prevent this situation from happening, acid-free paper and cardboard, polyethylene foam and fabric, and other well-known conditioning materials are preferred.

Then, each object being different, the storage needs to be adapted to its needs (size, weight, material sensitivity…) but also to the room available in the storeroom itself ! Concerning the jar, it was about allowing its safe and easy handling and preventing it from rolling.  According to its weight, the cardboard used had to be quite strong.

Left: the box has a front side that opens and a small compartment (on the right) to store fragments that couldn't be glued to the jar.   On the right: The box with the front side closed.

Left: the box has a front side that opens and a small compartment (on the right) to store fragments that couldn’t be glued to the jar.
Right: The box with the front side closed.

The mount, so as the jar can safely be pulled out of the box.

The mount, so as the jar can safely be pulled out of the box.

Left: the jar in its new storage box... Right: ...ready to go back to the Egyptian storeroom.

Left: the jar in its new storage box…
Right: …ready to go back to the Egyptian storeroom.

Here ends the conservation treatment of the jar; it was brought back to the storerooms last week. But we still have new projects in the Lab !

A new challenge in the lab

I am always pleased to see returning visitors to the Artifact Lab. And of course, people who have been here before want to know, what’s new? Visiting the lab is the best way to find out about our latest projects and progress, but this blog is the next best thing.

So, what is new around here? Well, I’ll let you take a look for yourself:

shabti boxThis object was featured in the “What in the World” series on the museum’s Facebook page this week. There were a wide range of guesses as to what this is; my favorites being a breadbox, an Egyptian mail box, a papyrus organizer, a holder for cat mummies, and an ancient Egyptian Matchbox-car garage.

Seriously though, this is a shabti box. Here is a shabti box that is similar in style, at the British Museum. Shabti boxes were used to house shabti figures. Shabtis were included in burials as servant figures that would carry out heavy work on behalf of the deceased. They were depicted as mummified and were inscribed with spells which, when recited, magically caused them to come to life and perform work for the deceased in the afterlife. Here are 3 shabtis that were originally housed in our shabti box:

shabtisThe shabti box and shabtis are made of wood, covered with a thin layer of gesso, and painted. They are in the lab for treatment because their surfaces are actively flaking. Not only is the paint flaking, but there is a yellow-orange coating over the painted surface that is badly flaking as well.

This yellow-orange coating is applied over the entire surface of the shabtis and the box (inside and out), and it is very thick in areas.

A detail of the shabti box showing areas where the coating is particularly thick (pointed out here with the red arrows).

A detail of the shabti box showing areas where the coating is particularly thick (pointed out here with the red arrows).

My first question is, what is this coating? Is it an original varnish or is it a later restoration?

The box and the shabtis date to the New Kingdom, ca. 1200 BCE. We know that varnishes such as those containing pistacia resin were used on painted wood in the New Kingdom, and these varnishes often appear yellow, although they may not have been yellow when first applied. We also know that these varnishes were applied unevenly – the application of the pistacia resin varnish has even been described as “messy” and it is acknowledged that its purpose was not an aesthetic one, but rather intended to make such objects more divine, or suitable for the afterlife (Serpico and White 2001). This description may help explain the rather sloppy appearance of the yellow-orange varnish on our shabti box and figures.

We cannot, however, discount the idea that this coating may be a later restoration. We know that archaeologists frequently stabilized artifacts in the field to allow for their safe recovery. Materials such as paraffin wax, gelatin, shellac, and cellulose nitrate have been used for this purpose in the field or once the objects found their way into museum collections (like the wooden heads Laura has been working on).

There are several ways in which we can try to determine what this coating is and when it may have been applied. We already have some clues, but we’ll share those in an upcoming post. Stay tuned for updates as we learn more!

 

Ungluing, re-gluing and filling the jar.

Statuette of an egyptian potter at work (beginning of  the 2nd mill. B.C).

Statuette of an egyptian potter at work (beginning of the 2nd mill. B.C).

The next step for the Egyptian jar was un-gluing all the fragments …to glue them together again.

We had two different cases: fragments that remained adhered together and fragments that were already separated, bearing remains of an old adhesive on their edges. The old adhesive had to be removed since it had many negative issues. First, it prevented the fragments from being joined back together by creating an unnecessary thickness at their junction. Moreover, when reconstructing the ceramic, the old adhesive prevents the fragments from fitting together well.

This old adhesive had a light brown color and after a few tests, it was found to swell when warm water was applied on it.

Here is what it looked like:

Detail of the break edge of one of the fragments, after applying water steam.

Detail of the break edge of one of the fragments, after applying water steam.

To remove the adhesive from the break edges, we used a Preservation Pencil, a tool looking like a pen and emitting water steam. Once softened, the adhesive was very easily removed with a scalpel or a brush.

And here is the result :

The same fragment edge after the removal of the old adhesive.

The same fragment edge after the removal of the old adhesive.

For the fragments still adhered together, it was a little more difficult since the water had to penetrate inside the jar but not too much because of the water-soluble ink on the surface. Compresses, or poultices, of water were applied on the interior of the ceramic, to cover the breaks. Most of the fragmentsfell apart quite quickly contrary to areas where the jar was very thick.

Now the building could begin ! … well almost since it was necessary to plan precisely how to proceed and in which order to arrange the fragments. First, we had to find where each of them was going, to estimate the losses. For that purpose every fragment was given a number and they were located on a map so as to keep track of their location.

The map; the numbers were indicated on the fragments with blue scotch tape.

The map; the numbers were indicated on the fragments with blue scotch tape.

Then the gluing really began, using the conservator’s favorite adhesive: Paraloid B72, diluted in acetone.

First steps of the gluing.

First steps of the gluing.

The more the jar grew, the more it needed a support, first on the outside, since its bottom is rounded….

A good support was provided by this bucket filled with glass balloons, heavy enough to stabilize the jar.

A good support was provided by this bucket filled with glass balloons, heavy enough to stabilize the jar.

…then on the inside to prevent it from collapsing on itself because of some particularly heavy fragments.

The jar was growing and needed internal support; the white material inside is a plastic bag filled with polyethylene fiber.

The jar was growing and needed internal support; the white material inside is a plastic bag filled with polyethylene fiber.

Losses in the ceramic had to be filled at the same time as the gluing to provide structural support to the jar and prevent it from collapsing.  Moreover those areas to fill would have been difficult to reach once the gluing was complete.

There was one large loss that definitely needed to be filled since one of the surrounding fragments was holding by only a few millimeters to another one.

Filling this area was a bit tricky. The fill material needed a support to be applied on the jar. Japanese tissue paper was glued inside of it and strengthened by applying several layers of Paraloid B72. It also needed to be shaped according to the curve of the jar.

On the left: The area to be filled.                        On the right: Japanese tissue paper used as a support to hold the fill material.

On the left: The area to be filled.  On the right: Japanese tissue paper used as a  support to hold the fill material.

On the left: The inside of the jar with the "tricky fragment" held in place by the japanese tissue paper.   On the right: Applying the fill material.

On the left: The inside of the jar with the “tricky fragment” held in place by the japanese tissue paper. On the right: Applying the fill material.

The fill material used is a mixture of Paraloid B72 and glass micro-balloons, looking like a very light white powder; plaster is also traditionally used to fill losses, but glass micro-balloons are lighter and don’t bring any salts to the ceramic. That kind of fill is also reversible and completely neutral towards the ceramic.

Here’s the fill once finished and polished with a heat spatula, ready to be painted.

The fill almost finished: the building can go on.

The fill almost finished: the building can go on.

More fills and building to come in a next post !

 

 

Cleaning the jar

Detail of the black inscription covering the jar.

A previous post introduced you to this demotic jar, currently on view in the Lab. The first step in its treatment was to clean the surface, which was very black due to dust.

It was necessary to make some tests on the ceramic to determine which way to clean was the best, meaning the safest for the object. Indeed, the black inscription on the jar is fragile and water sensitive. The first rule was to choose a non -aqueous method, that’s why I first thought about…erasers !

Image showing cleaning tests on a fragment of the jar.

Image showing cleaning tests on a fragment of the jar.

Test 1 : Sanford Magic Rub Eraser. index Test 2: Staedtler stick eraser.stadtlerTest 3 : Latex eraser.

Test 4: Ethanolethanol

Test 5: Wishab eraser.wishab

As you can see on the picture, the erasers seem to be the best choice, especially the n.2. Indeed, it can be applied with different levels of strength according to the amount of dust to remove.

Ethanol was also to be tried, being a “light” solvent; but the issue with a solvent is that you can’t control how it penetrates in the material, especially with a porous ceramic. So the best choice seemed to be the Staedler eraser.

It was then time to test this cleaning method on the inscription.

P1040678

Cleaning test with the eraser on an inscribed fragment.

The eraser appeared to work well, removing only the black grime and not the inscription. Of course, one has to be careful with this method, and not to press the eraser too hard or the black ink could disappear as well !

So I went on and cleaned all the other fragments.

Fragment before cleaning.

Fragment before cleaning.

The same fragment after cleaning.

The same fragment after cleaning.

 

In a general way, cleaning an object is very rewarding for a conservator, because the result can be seen at once. And pictures taken before and after are often impressive.

However, some things could not be improved; many demotic signs are lost due to water damage that occurred in the burial environment so the text isn’t complete. Moreover, a few fragments didn’t change after being cleaned, and still look dusty even if they aren’t.

Here is the general result, after all the fragments were cleaned.

General view of the fragments before cleaning.

General view of the fragments before cleaning.

view after step1

General view of the fragments after cleaning.

Next step: de-gluing the fragments !

 

A demotic jar

A pottery workshop (from LICHTHEIM Miriam, Ancient Egyptian literature, 1973)

A pottery workshop (from LICHTHEIM Miriam, Ancient Egyptian literature, 1973)

Among the objects that an archaeological conservator treats, a very important one regarding the quantity is ceramic. Ceramic artifacts are widespread on time and many very different places; a lot of (if not all) civilizations on Earth made ceramics, so if you haven’t met one of those yet in a museum, it’s only a matter of time!

The one we have in the Artifact Lab is an Egyptian jar, from one of the past Penn Museum’s excavations on this site. Jars were used to contain fluids and are covered inside with a mixture of water and clay, to make it waterproof.

Here is a picture of the fragments before any intervention:

The jar before treatment.

This ceramic is covered with inscriptions painted in black ink (most likely a carbon ink) and the writing appears to be demotic. The Egyptian writing knew three different forms: hieroglyphic, which is the one you’re used to see on monuments; hieratic, which is a simplification of hieroglyphs, allowing the scribes to write faster for their administrative work on papyrus or pottery and rock fragments; and the demotic is a simplification of the hieratic, used from the VIIth century B.C. It is one of the writing that you can see on the Rosetta Stone.

rosetta stone

Demotic writing on the Rosetta Stone.

Detail of the black inscription covering the jar.

Detail of the black inscription covering the jar.

This black ink is water soluble, meaning that water is highly prohibited to clean the inscribed areas !

Concerning its condition, the main problem of course is that the jar is broken into about 50 fragments. It was restored in the past so it still bears remains of an old adhesive on the edges and many fragments are still glued together. Moreover, the surface and the inscription are covered with dust and need to be cleaned.

P1050012

Example of a particularly dirty fragment. The inscription is barely visible.

The next step will be to remove the old adhesive and to put the fragments together again. Eventually, we may have to fill some gaps in the ceramic, so as its handling could be easier and safer.

Those steps will be more detailed in several blogposts to come !

 

About two wooden Egyptian heads…

“You have a wonderful job!” It’s a sentence that a conservator often hears. But what is really this incredible job? I propose to you to have a closer look at what a conservator usually does by following step by step the conservation of two artifacts recently arrived in the Artifact Lab.

Laura blogpost1Not really the glamorous objects you imagine when you think about Ancient Egypt, right? But they can reveal so many things to us.

Let’s begin with all what we knew when they arrived in the Lab: these artifacts are two Egyptian wooden statue heads. They bear remains of polychromy (blue and red painting) and have inlaid eyes. In their storage drawer were three labels: one quoting a publication about Dendera (the place where they were excavated) describing the heads, and two others mentioning a previous treatment in 1965 with an adhesive called Vinylite.  Other information about these objects came from our curators, who knew that the heads are from the site of Dendera, more precisely the mastaba of Adu II, excavated by Flinders Petrie, a famous British archaeologist. Moreover, the heads are from the Sixth dynasty (2374-2140 BCE). That’s all we knew about those two heads before beginning our work !

Let’s have a closer look at them…

Left: one of the wooden heads viewed in profile Right: a front view of the other wooden head

Left: one of the wooden heads viewed in profile.  Right: a front view of the other wooden head.

A long quest is ahead and we’re only starting to think about an appropriate conservation treatment. Indeed, before any scalpel reaches their surface, we need to gather as much information as possible about the artifacts. Stay tuned to hear more about our discoveries and the decisions that we make based on what we learn.

 

Wrapping up the cat mummy

Speaking of Abydos, let’s get back to our cat mummy, which was excavated from a cemetery there back in 1901-02. Our summer intern Anna O’Neill will describe how she carried out the conservation treatment on this very fragile object:

Hello again.  You may remember that last time I wrote about this cat mummy, I got a little distracted.  But this time I’d like to focus on the treatment process.  Many of our mummies are in remarkably good condition, with wrappings that are stable and that can withstand handling (albeit with care).  Not so with this cat.

cat mummy 1When plant-based fibers age, the cellulose that gives them structure decays and the fibers become brittle.  Badly aged linen can fall apart at the lightest touch, leaving loose fragments and powder on the surface of the object.  The linen on top of this cat mummy was torn and obscured by dust, but the real problem was underneath.  Prior to treatment, Molly and I carefully turned the mummy a little so we could see below—and quickly (but gently) put it back!  As you can see in the image below, the layers of linen were falling apart and the threads that had criss-crossed the layers were broken and hanging off.

cat mummy 2We decided to wrap the mummy in nylon netting, which would hold everything in place while keeping the surface visible.  This would be a non-invasive, completely reversible process that would allow the mummy to be safely handled and studied.

Before wrapping, I gave the mummy a light surface cleaning with a variable-speed HEPA-filtered vacuum.  Using a nozzle attachment fitted with a screen, I carefully removed the powder on the top of the mummy.  The linen—though torn—was still soft and flexible, like modern fabric.

cat mummy 3Then, I toned the netting to match the color of the mummy using acrylic paint.  Once the paint was dry, I positioned the netting across the top of the mummy and pinned it in place.  The flip was simple but nerve-wracking—we knew from our quick peek earlier that the underside was in bad shape, but we didn’t know to what extent.  With Molly’s help, I turned the mummy over so that all of the powder, torn linen and broken threads were now on top.

cat mummy 4Since the thick layer of compressed linen powder completely obscured the wrappings below, I again vacuumed the mummy, using a screen to filter out the powder while keeping everything else in place.  A vacuum may seem like an odd conservation tool (I got some weird looks as I hoovered the cat), but with the filter over the nozzle and variable suction control, there’s no danger of sucking up the entire object.

cat mummy 5

The underside of the mummy after cleaning. It may not look like much, but it’s better!

With the underside of the cat finally visible, I sewed the netting up the middle using a flat-felled seam.  As the name implies, this created a neat seam with a flat profile.

cat mummy 6

Overall view of the underside of the cat mummy (after treatment)

Overall view of the top of the cat mummy (after treatment)

Overall view of the top of the cat mummy (after treatment)

Now that the linen wrappings are encapsulated, the little cat mummy can be handled and studied, and it can (hopefully) be x-radiographed this fall.  It still may not have its head, but at least it won’t be losing any more of itself any time soon.

 

The “conservation story” of Nefrina’s Funerary Mask, Part 3: Stabilization of the Exterior

This is the final installment of the conservation treatment of Nefrina’s Funerary mask.  The condition and stabilization of the interior have been discussed in previous posts.  In this post, I will be talking about building the storage and display mount as well as stabilizing the exterior of the mask.

1.  New mount construction:  Once the interior structural issues were addressed, I made a new mount for the object. I carved Ethafoam, an inert polyethylene foam, to create a support for the top of the head, and used epoxy putty (the black material in the images below) to create a form-fitting rigid support. The clear plastic in the image below is cling film, which I used to keep the epoxy from bonding to the mask while it cured.

The mount is in three separate detachable parts. Part 1 supports the top of the head and the face, part 2 supports the front and back panels of the mask, and part 3 is a stand to hold parts 1 and 2 during travel and storage. Parts 1 and 2 of the mount are supporting the mask at this moment while it is on display (along with a pole mount that has taken the place of part 3).

Left: During treatment photo showing the construction of the top portion of the mount. Right: The completed mount.

Left: During treatment photo showing the construction of the top portion of the mount. Right: The completed mount.

2.  Facing removal: Once I completed the mount and put it in place, I flipped the mask over again and started to remove the temporary facing of Japanese tissue. I removed the facing in sections and stabilized the exposed areas before moving on to a new area. I did this by brushing an area of facing with acetone, which solubilized the adhesive that had been used to place the facing, and then gently pulling the Japanese tissue back.

Facing removal

Carefully removing the Japanese tissue facing

3.  Re-shaping before tear repair: Some of the tears did not go through all of the linen layers, and so could not be treated from the interior. These tears had to be realigned and repaired from the front. As with the inside, I often had to humidify and re-shape an area before carrying out the repair. The images below show the tear in the forehead of the mask during reshaping. I used Teflon tape to bring the edges of the tear together.

During reshaping of the tear in the forehead

During reshaping of the tear in the forehead

4.  Tear repair: I repaired the tears using paper pulp combined with methyl cellulose and powdered pigments. Before applying the wet pulp, I lined part of the areas with a thin sheet of dried paper pulp mixture to achieve an even fill.

Left: lining the area with dried paper pulp and methyl cellulose. Right: After filling tear repair with additional paper pulp mixed with methyl cellulose.

Left: Lining the area with dried paper pulp and methyl cellulose. Right: After filling with additional paper pulp/methyl cellulose mixture.

5.  Edging: Many areas of the paint were adjacent to areas of loss and were cracked and cupped. I stabilized these areas by edging the paint with paper pulp combined with methyl cellulose and powdered pigments.

Side of the mask after edging the areas of unstable paint

Details of the side of the mask after edging the areas of unstable paint

6.  Loss Compensation: Large areas of loss on the edges of the mask also had to be filled for the mask to be structurally stable. I filled the areas of loss by applying pigmented paper pulp mixed with methyl cellulose across the areas of loss using a backing support of silicone-coated Mylar. The coating on the Mylar allows it to be removed once the paper pulp mixture had dried.

Left: During loss compensation.  The square rare earth magnet at the bottom of the image was being used to keep the Mylar in tight with the shape of the mask. Right: After the fill was done and had dried.

Left: Detail during loss compensation. The square rare earth magnet at the bottom of the image was used to align the Mylar along the contours of the mask. Right: After the fill was complete and had dried.

7.  In-painting: Although I had pre-toned the fill material, the fills still needed just a bit of in-painting to adjust the color so that it would blend in better with the mask.

Left: Tear on the head after treatment. Right: Area of loss on the side of the mask after treatment.

Left: Tear on the head after treatment. Right: Area of loss on the side of the mask after treatment.

All of this work allowed Nefrina’s Funerary mask to travel for exhibition in the Reading Public Museum, and to be exhibited here at the museum, In the Artifact Lab – visit us to take a closer look at the mask for yourself, and to see several other objects that have recently been conserved.

- posted by Tessa de Alarcon