Articles tagged with: air abrasion machine

Thinking of doing a work placement? My experience with CMAS

on Wednesday, 29 August 2018. Posted in Conservation, History Centre

I can’t believe that the first year of university is over! It goes so fast and with so much information it can be a bit overwhelming, but trust me, all that hard work and studying will pay off. The Conservation of Objects in Museums and Archaeology undergraduate course at Cardiff introduced me to a whole new world of practical science, as well as in-depth theory, of conservation materials and specialised equipment, such as x-ray and air abrasion machines. By the end of the year I felt pretty confident with the concept of conservation but was still nervous on how to actually apply the theory with real, archaeological objects; in a true work environment.  This is where a work placement comes in. My first-year placement was at the Wiltshire and Swindon History centre, as part of the Conservation & Museum Advisory Service (CMAS), a commercial business which deals with issues both in museums and in public collections.

Although it can seem daunting at first, this experience is essential for developing those practical skills and applying the theory with real, archaeological objects, as well as understanding the treatment of different materials and the ethical choices conservators must make; focusing on what’s best for the object and adjusting treatment plans with the client’s wishes accordingly. Keep in mind that work experience is for your benefit, so don’t panic when you have millions of doubts and questions because the people you work with are there to help you (even if you ask questions every 5 mins).

So anyway, onto the actual conservation, hooray!

First things first, you will need to assess the object just by looking at it and writing up a condition report, which simply states any observable issues with the object. The majority of my time was spent working with a Roman ceramic oil lamp in the shape of a foot! Quite a fun object from Chippenham Museum, but as you can see there is a bit of a messy application of adhesive around the centre of the lamp where it has broken in two and was re-joined.  There were also scratches, dust and cobwebs on the inside, layers of red dirt/soil on the surface as well as white flaking corrosion (see figures 1-4).

Before treatment:

Figures 1-4

Ok, so the lamp required a good clean and that adhesive definitely needed to come off. Ultimately, the decision was to completely remove the adhesive and undo the join so that I could re-attach the two pieces with a better, cleaner join.  In order to remove the adhesive, I needed to work out what solvent it was soluble in. For this, I took small samples of the adhesive from the lamp by slicing off some of the softer areas with a scalpel, under a microscope.  I then put the samples into a petri dish and tested them with different solvents (see figures 5 & 6).

Testing solvents on the adhesive:

Figures 5-6

After about 30 minutes, I could see which solvent made the adhesive go soft and rubbery. The process of removing the adhesive required quite a lot of patience as the it didn’t want to budge; a scalpel was used to remove larger chunks of the adhesive and a poultice was placed around the join. A poultice was a way of creating a solvent environment to help loosen the adhesive and separate the two pieces. 
 *Just to give you an idea of the tools used in this process, I’ve taken a couple of photos for reference.

Figure 7 From left to right – pin vice, plastic tweezers, scalpel, wooden stick and cotton wool

Figure 8

In conservation, we usually make or own cotton swabs by using a bamboo stick or cocktail sticks (depending on what you’re working on) instead of regular, pre-made cotton swabs.  Making your own means that when the cotton gets dirty it can be easily replaced and the size of the swab can be varied so you can get into the small nooks and crannies that need a good clean. It also means that we aren’t throwing away millions of cotton swabs and being more environmentally friendly.

After many tries, the poultice wasn’t loosening the adhesive, so I went in with the scalpel and pin vice to try and dig out some adhesive in the join. Another poultice was then left on for a couple of hours. When it was removed I was able to gently pry apart the two pieces (finally!) and clean the new surfaces (see figure 9).

Conservation of a rare Visigoth Brooch

on Thursday, 23 March 2017. Posted in Archaeology, Conservation

Conservation has been undertaken on a rare Visigoth Brooch here at the Wiltshire and Swindon History Centre. We were honoured with a visit by the finder of the artefact Matt Smith, who came for a tour of our facilities and to view the work being undertaken.

Matt Smith holding the brooch

Thought to be only the second of its kind found in the country the iron and copper alloy brooch has been identified as a late 5th, early 6th-century AD type, predominantly found in southern France and central Spain. The brooch was uncovered during excavations undertaken by Operation Nightingale and Wessex Archaeology at Barrow Clump on Salisbury Plain.

The brooch formed part of the grave goods associated with one of the female burials on the site, and Matt’s first solo grave excavation. Significantly, well preserved organics remain on the surface of the object with the weave of the fabric visible through the microscope.

Image of the brooch after conservation
Microscope view of the fabric weave

The brooch arrived at the conservation labs after x-radiography revealed the decorative copper alloy inlay. Still covered in corrosion products and soil from the burial environment, clues to the presence of preserved organics were just showing through the soil covering. Cleaning started slowly with scalpels and pins under the microscope to remove the soft chalky soil and reveal the extent of the organics.

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