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!

 

Peptide Mass Fingerprinting (PMF)

Motivated to learn more about the fur and animal hair found in our Predynastic mummy bundle, I popped up to Boston yesterday for a workshop entitled “Identifying collagen-based materials in cultural objects using peptide mass fingerprinting“.

The workshop was organized by a group at Harvard, including the Peabody Museum of Archaeology and Ethnology in collaboration with the Straus Center for Conservation at the Harvard Art Museums and the Harvard FAS Division of Science. The team received NCPTT funding for a project to develop a new application of an analytical technique called peptide mass fingerprinting (PMF).

PMF uses mass spectrometry to analyze very tiny samples of proteinaceous objects and identify the mammalian source to the species level. It actually can be used to analyze materials made of collagen and keratin, but the group at Harvard is focusing on collagen-based materials. The procedure essentially breaks up the protein into smaller peptides, and the mass of the peptides is measured using a mass spectrometer such as a MALDI-TOF. The peptide masses are compared to known reference samples, which allow for identification. This type of analysis falls under the category of proteomics, or the large-scale study of proteins, and it is sometimes referred to by this name as well.

The Harvard project is focused on applying this technique to objects made of gut, skin, sinew, and membrane from Alaska, the Northwest Coast, Northern California, and the High Plains. Another goal of the project is to bring this type of analysis, which typically takes place in large industrial or academic labs, to museum labs. You can learn more about the project on their blog.

The workshop included 3 presentations by the project’s primary analytical investigator/scientist Dr. Dan Kirby, project research associate Madeline Corona, and Kress fellow Ellen Promise. Between the 3 of them, they covered how PMF works, what it can tell you, and how it is applied to cultural artifacts, using a project on Alaskan kayaks as a case study.

After Q&A led by Peabody Museum conservator T. Rose Holdcraft, we were led on a tour of the Peabody conservation lab, where we were able to feast our eyes on some of the impressive Native Alaskan objects that they are investigating as part of the project.
A view of the Peabody Museum conservation lab, with several Native Alaskan skin and gut objects on view

A view of the Peabody Museum conservation lab, with several Native Alaskan objects on view

We also toured the impressive Mass Spectrometry and Proteomics Resource Lab, where we had a chance to see the Bruker MALDI TOF/TOF instrument and a demonstration of how samples are prepped for analysis.
The Bruker MALDI-TOF/TOF instrument and Madeline Corona demonstrating sample prep

The Bruker MALDI-TOF/TOF instrument and Madeline Corona demonstrating sample prep

The sample prep area showing the equipment used, including the MALDI plate (lower right)

The sample prep area showing the equipment used, including the MALDI plate (lower right)

Here at Penn, we are excited by this technique – not only for the minute sample size required (the samples used are just barely detectable to the naked eye) but also for its accessibility. We have a lot of animal-based materials in our collection and we are hoping to pursue using PMF to analyze these materials. Actually, we are already working to see if its possible to use this technique to identify the sources of the fur and basketry hair fibers from our Predynastic mummy, thanks to help from Smithsonian MCI fellow Caroline Solazzo, whose work focuses on keratin-based materials. PMF supposedly works on all types of samples, including those that are very old and/or are in poor condition, so we thought we’d put this to the test by starting with samples from our oldest Egyptian mummy (he’s well over 6000 years old). We will let you know how it seems to work.

A side note – a quick trip to Boston wouldn’t be complete without a stop at the Museum of Fine Arts. I spent most of my time there ogling the Ancient Egypt exhibits, admiring the massive, yet delicately decorated and inscribed coffin boards of Djehutynakht’s outer coffin (same time period and style as Ahanakht’s coffin)

The interior of the lid of Governor Djehutynakht's outer coffin (left) and detail of the false door (right)

The interior of the lid of Governor Djehutynakht’s outer coffin (left) and detail of the false door (right)

and many of the other treasures of this collection, such as this bead net dress made of faience and gold from the 4th Dynasty.
Detail of a 4th Dynasty beadnet dress (ca. 2551-2528 BCE)

Detail of a 4th Dynasty beadnet dress (ca. 2551-2528 BCE)

Breathtaking, really. I also found this shabti in a miniature coffin very charming.
Shabti of Queen Neferu with  miniature coffin, from Deir el-Bahri, tomb of Queen Neferu, 11th Dynasty (ca. 2061-2010 BCE)

Shabti of Queen Neferu with miniature coffin, from Deir el-Bahri, tomb of Queen Neferu, 11th Dynasty (ca. 2061-2010 BCE)

And while the MFA does not have conservators working in a gallery, as we are doing here at Penn, they do have some great “behind the scenes” galleries, one with interactives that engage visitors to think about conservation ethics and decision making. One of my favorites was an example using Maya Cylinder vases, examining condition issues and treatment decisions.

Some screen shots of the Maya vase example in the MFA's "behind the scenes" gallery

Some screen shots of the Maya vase example in one of the MFA’s “behind the scenes” galleries

All in all, a great trip. We’ll keep you updated on the whole peptide mass fingerprinting technique and how we might be able to use this for our collection.

 

More about our Predynastic mummy

Last year we posted some information about Bruce, our Predynastic mummy (and the oldest Egyptian mummy in the museum) here in the lab. Bruce has been on ongoing project, but he is often tucked toward the back of the lab unless we are actively working on him. While he’s often not front-and-center, when visitors enter the gallery and they catch a glimpse of him, they know that he’s special, even if they don’t know what he is, exactly.

Bruce on his cart, near the back of the lab, as viewed through the Artifact Lab windows.

Bruce, near the back of the lab, as viewed through the Artifact Lab windows.

As soon as he is spotted, I am often asked “what is that?” “is that a mummy?” and “what are you doing with him?”. In conservation, we are not always actively treating objects (or in this case, mummies); some of our projects involve close examination and study of objects (often referred to as technical studies). These technical studies may be a precursor to conservation treatment, but they may also be independent of treatment.

We are not currently carrying out conservation treatment on Bruce. Our focus at the moment is careful examination and some analysis, in consultation with other specialists. At the moment, we are focusing on trying to identify the type of animal hide that he’s wrapped in:

The red arrows are pointing out pieces of the animal skin bag wrapped around Bruce.

The red arrows are pointing out pieces of the animal skin bag wrapped around the mummy.

and also the animal hairs used to make the finely woven baskets included in his burial bundle:

E16229_basketsThese baskets are actually made of plant and animal fibers – the baskets are twined, and the passive elements (or warps) are made of plant fibers, while the active elements (wefts) are made of light and dark animal hairs. We know that the wefts are animal hairs based on our examination of these fibers using our polarized light microscope (PLM).

Views of the light-colored hair (left) and a cross-section of the hair (right) at 100X magnification

Views of the light-colored basketry fiber at 10X (upper right), at 50X (lower left), and a cross-section (lower right) at 200X magnification

Views of the darker hair (left) and a cross-section of the hair (right) at 100X magnification

Views of the darker basketry fiber at 10X (upper right), at 100 X (lower left), and a cross-section (lower right) at 200X magnification

Sometimes animal hair can be identified based on the features observed under a microscope, by comparing the unknown hairs to known reference samples. Some great animal hair ID sources on the web include this great resource on the FBI website and the Alaskan Fur ID website.

While we can clearly see that these fibers from the basket are animal hairs, we have not been able to identify them based on microscopy alone, so we are pursuing other analytical methods of identification, such as peptide mass fingerprinting (PMF). PMF uses a mass spectrometer to analyze the peptides in a proteinaceous sample, which can identify mammalian material to the species level using a micro-sized sample. Next week, I am attending a collagen identification workshop at Harvard, where I will learn more about PMF and its application to cultural artifacts.

We are excited by the possibilities this technique offers – being able to identify the skin(s) Bruce is wrapped in and the materials used to make the baskets found in his bundle will add to our understanding of very early technologies and funerary practices in Egypt. We will certainly share our findings as we learn more.

 

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

 

 

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.

 

Au revoir, Laura!

Since September, we have been very fortunate to have Laura Galicier interning with us in the Artifact Lab. Laura is a graduate student studying conservation at the University of Paris Pantheon-Sorbonne, and spent her time here working on the conservation of several objects, two of which (the wooden heads) are the basis for her dissertation.

laura with headsLaura will soon graduate with her degree in conservation, and will embark on the next phase of her career as a conservator.  Although Laura’s final day in the lab was last week, have no fear – you haven’t heard the last from her. She has at least 1 more blog post to contribute, which will be available soon.

Congratulations, Laura!  Félicitations!  We will miss you. And these guys want to know, when will we see you again??

heads goodbye laura

A new material in the Lab

loadimg.phpWhile we primarily work on Egyptian materials in the Artifact Lab, we occasionally work on objects from other cultures as well. (http://www.penn.museum/sites/artifactlab/2013/12/21/ch-ch-changes-in-the-artifact-lab/) Recently, two new objects were brought to lab. They are two glass vessels from Cyprus, which were discovered in the archaeological site of Kourion. Their date is unknown.

Untitled-1Capture

First of all, what is glass made of? Generally three materials are mixed together:

- A former, being the main component: silica, usually found in sand;

- A flux, lowering the melting point of the glass mixture, the melting point being the temperature at which the glass mixture becomes a liquid (from 1600-1713 Celsius for raw silica alone to 800 Celsius for silica + a flux); this material is an alkali or soda.

- A stabilizer, inserted inside the chemical structure of the glass to strengthen it; usually lime.

- A fourth material, metal oxides, can be added to obtain a specific color (manganese for purple, gold for red, silver for yellow…).

This composition and the percentages of each substance change according to times and places. Moreover, glass can take a wide range of different shapes.

Here is a picture of the objects before treatment:

The two glass objects before treatment.

The two glass objects before treatment.

Both are glass vessels. The vessel on the left was restored in the past; a coating was applied on its whole surface and it was glued with that same substance. This adhesive is now flaking off the object, leaving thin and transparent films. This become more obvious when observed under ultraviolet light.

The object viewed under UV light. The bright white-yellow material is the old adhesive.

The object viewed under UV light. The bright white-yellow material is the old adhesive.

The old adhesive is pretty obvious now, with its white-yellowish color. This substance is also soluble in acetone. These properties allowed us to conclude that it is cellulose nitrate, a well-known material used to restore glass objects in the past. In addition to not aging well, this adhesive was applied very thickly on the edges, preventing the fragments from being joined together correctly.

Example of a problematic cellulose nitrate deposit on the  edge of a fragment.

Example of a problematic cellulose nitrate deposit on the
edge of a fragment.

Both glass objects also show evidence of delamination of their surfaces. It takes the form of a white layer, which flakes off the object.

New Picture (3)This phenomenon, called delamination, can start in the burial environment especially when the object undergoes weathering. This weathering changes the refractive index of glass as well. Each glass artifact has a specific refractive index, indicating how the light passes through it. According to this, our eye will perceive the object a certain way. Any change in the material, such as delamination, will alter this refractive index and thus our perception of it.

Untitled-10Here is an illustration directly on the object itself:

Delamination of the glass; the delaminated layers are white whereas the ‘glass substrate’ show a brown amber color.

Delamination of the glass; the delaminated layers are white whereas the ‘glass substrate’ show a brown amber color.

This process, if not stopped, can end up delaminating the whole object, layer by layer, resulting in the loss of this artifact. Conservation treatment, and good environmental controls, can prevent this from happening.

We’ll write more about the treatment of these glass vessels in our next post!

 

 

 

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 !