English

Amgueddfa Cymru

Hafan

Blog yr Amgueddfa

Amgueddfa Cymru

Everything has now been recorded, so the next step is to lift the pins! The decorative pins were once attached to an organic material, possibly leather, this has now gone, replaced by soil and once the soil has been removed there will be nothing holding the pins together. So the challenge is to lift and conserve the pins in such a way to preserve the original fish scale pattern and any dimensions of the group, which may help identify this mystery object in the future.

A bit of a challenge, so I decided to lift only small sections at a time, which does mean breaking up the largest surviving section unfortunately, but I should be able to reconstruct this later.

In the first image you can see that some of the pins are facing up and some facing down, indicating that the material the pins were once attached to was folded, this has perished leaving the pins in this position. So now it’s not just a mystery object it’s also a layered mystery object! Oh joy!

On the next image, outlined in white, is the first section to be tackled; I thought I’d start with the smallest and simplest first! The upper surface of the pins is faced up with Japanese tissue and adhesive. Once dry I excavate round and under the section then lift and turn it over.

Not as straight forward as I thought as something new appears, not just pins, but a disc headed stud. The x-ray also reveals the remains of a chain, plus a line of dome headed studs

On cleaning, the chain can clearly be seen attached to the stud and would have once been suspended from it, possibly linking up to another stud elsewhere on the armour. There are also enough dome headed studs running in a line to suggest they were part of a deliberate pattern. The remains of a tinned surface and therefore white metal finish survive on the upper surface of the stud and at the end of the pin there is a washer or rove identical to that on the plaque featured on the previous blog. So there is a good chance that they were once part of the same object, but again it’s too early to be sure.

The disc and pins are now cleaned and preserved, in the last photo they are laid out as they were in the ground. The dome headed pins were in direct contact with the disc suggesting they were on the same layer as the stud, which was facing downwards in the soil and attached to something folded under the layer with fish scale pins, which were facing up. Hope that makes sense!

Now to tackle the next section and I have a feeling that this may be full of surprises as well.

The second significant object in the same block as the pins (highlighted in the previous blog in this series) is an unusually shaped bronze sheet decorated with a stud depicting a human head. The head is wearing what appears to be a Phrygian cap. This type of soft, conical shaped hat with the top flopping forward was originally associated with people from the eastern part of the Roman Empire.

The head, cast in solid bronze, measures from ear to ear about 2cm. Soil and debris obscure the detail but I can see under this the features of a face peeking through, including large almond shaped eyes and curly hair poking out from under the cap. Looks a bit of a mischievous character to me!

The bronze sheet is an odd shape too; the edges are damaged and eroded in places. I’ve indicated with a black line the surviving edges I can be sure of. The damage on the other edges means unfortunately that they may not reflect the original dimensions of the object.

The sheet is not flat either, these bends and folds in the metal look like they were made in antiquity as the original patina is still smooth and undamaged around these areas. If the metal had been bent after the green patina was formed then this fragile surface would have cracked and flaked off revealing the metal below. So was this metal sheet originally wrapped round something more three dimensional? Difficult to say at this stage, it is also possible it got damaged in antiquity when flung on a pile of other armour and scrap, before it finally got buried. It’s amazing such delicate objects have survived at all!

When the sheet was lifted and turned over, four metal pins were found protruding out of the back. One, in the middle, belonged to the decorative stud; the pin had been punctured through the sheet to secure it. The three smaller pins are part of the sheet, created during the original casting by the looks of things.

Where the metal had been lifted there was a dark stain in the soil, probably the only evidence we will ever have that an organic material was once present. Among this there were fragments of a small doughnut shaped object. On further examination its original location could be identified as it was dislodged when the plate was lifted. The object lined up with the central stud and is in fact a washer or rove associated with securing items to leather. Two other tiny roves were found and all 3 have now been reattached to the pins at the back of the sheet. These now give us an indication of the thickness of the original backing material, which is about 3mm. The possible association with leather links this object to the pins lying near by. These were also applied to a flexible backing like leather; therefore there is a strong possibility that these artifacts were part of the same object, but more work has to be done to establish this.

Excavation of Roman Armour from Caerleon

Penny Hill, 15 Tachwedd 2011

The large block of armour was initially far too heavy to lift in one piece, so we had to split it into three. Julia has been working on the largest section (see previous blog) and I’m now excavating one of the smaller blocks.

At first glance this second block contains a number of interesting objects. A piece of bronze sheet with a cast head, a plain bronze disc, scale armour, a selection of iron objects (not yet identified) and something composed of rows of overlapping flat headed pins, similar in appearance to drawing pins. At this stage it’s difficult to tell if these objects are associated or not.

The most striking object in the block is the cluster of overlapping disc headed pins that have been laid down in rows and imitate scale. When new and brightly polished the copper alloy discs would have shimmered and caught the light. They are now very fragile, little metal remains and their shape is preserved by the green copper corrosion products. Retrieval and conservation is going to be fun and probably age me about 10 years!

The pins were once attached to a backing, probably made of leather which would have been flexible and allowed movement. This has now perished, leaving a black stain in the soil. I’ve kept samples so we can have a closer look at this later. However, the thickness of the backing material can be established by measuring the distance between the head and the bend in the pin.

Now the backing has gone, the soil is the only thing keeping the pins together. It’s going to be a challenge lifting them and preserving the pins original association. This is vital though as it might help identify this mysterious object .

In a time before modern mechanisation it is hard to work out how the Romans managed to make such small and perfectly formed little pins. A closer look down the microscope reveals interesting manufacturing marks but doesn’t really help with the intriguing question, how did they make them? On closer inspection different types of pins have been used, some are domed, some flat and there are also slightly larger studs, which may indicate that the pins were possibly laid in a pattern. I've put a few pictures up just in case anyone has seen an object like this before or fancies a challenge and work out how these little disc headed pins could have been made?

As mentioned in the previous post, the only way to advance the study of this large blocklift was to take x-rays of the excavated ‘features’, in order to get a better idea of the condition of the archaeological metals, and to see if there were objects beneath the ones excavated. For this to happen, the five features had to be separated and lifted in miniature blocklifts.

As readers can see by the first photograph which shows the whole soil block after the completion of micro-excavation, separating features was a difficult task: whilst feature 1 was a discrete item, easily removed from the rest of the block, I had to make certain executive decisions about breaking up the rest of the block. Where possible, I tried to divide the features from each other using the cracks that were already present in the block, or by cutting over and under overlapping features. Inevitably, some damage did occur to the peripheries of features during the lifting process.

The process of blocklifting was remarkably easy: effectively, I blocklifted these features in the same way that they were lifted on site, except that as I was working in a laboratory, I had the opportunity to use conservation-grade materials in a much more controlled environment.

To begin with, I had to stabilise the artefacts in preparation for a process which would jar them quite a lot. I first consolidated the exposed artefacts using a removable adhesive called Paraloid B72, and then added a layer of melted wax, called Cyclododecane, to provide a more intimate support. Handily, this layer will eventually sublime by itself.

I then wrapped features in Clingfilm, to act as a barrier layer between the archaeology and the rigid material I would use hold the block together. For this, I selected polyurethane foam (readers may have come across this whilst completing DIY projects; it is often used as an insulating filler), as it has a very low density, and will not interfere with the attainment of an image of the mineralized iron plate. Polyurethane is prepared by mixing two liquid components together, and could be poured around the covered feature, reaching all nooks and crannies. Walls of plastic card and clay had been built around the feature to enclose the polyurethane.

Once the polyurethane had hardened, I began to pedestal the feature being lifted, before undercutting it. The separated feature could be turned over, and large amounts of extraneous burial deposit removed, which would have otherwise interfered with x-raying the metal artefacts.

I repeated this process until all the features were lifted, and prepared for X-radiography.

After having managed to break the large soil block up into small enough blocks to get into the x-ray machine, I finally began the task of x-raying the archaeological artefacts.

For this, I had the chance to use the Museum’s newly acquired computerised radiography system. Here, instead of using the traditional wet-plate method requiring film and much time spent in a dark room, we use a phosphor plate which can be used around 1000 times. This plate is read by a scanner, and an image produced within about 45 seconds.

This new system has allowed us to capture so much more detail about the inside of the blocks and the condition of the armour than would ever have been possible using the traditional method. The x-ray records the density of materials at every point, and the software used to view the image allows for manipulation in much the same way as programs like Photoshop: we can zoom into areas of the image, adjust brightness and contrast, apply filters, invert the negative, etc. Thus far all of the features have been x-rayed, and the results have been astounding: I have included copies of the images, complete with annotations. It would appear that a lot more existed beneath the surface excavated than previously supposed.

I had hoped that the x-rays could be used as a guide for further excavation of the features and eventual extraction of the artefacts: however, the condition of the metal inside suggests almost complete mineralization of the iron, and cautions against this course of action. The most that can really happen with these soil blocks now is that they are extensively x-rayed, and stored safely in case of future research.

Aside from highlighting areas of interest on the x-rays, and explaining certain phenomenon, my role as conservator for this project has come to an end. Now, curators, archaeologists and specialists will have to identify objects in the x-rays, marry up these images with the photographic record of my excavation, and begin to tie this information into the narrative of the site overall.