Conserving Beirut's shattered glass

On 4 August 2020, a colossal explosion rocked the city of Beirut, levelling surrounding buildings and damaging others up to 10km away. The Archaeological Museum at the American University of Beirut (AUB) was one of the many cultural institutions affected. A case displaying 74 glass vessels was smashed against the floor, mixing thousands of shards of ancient glass with fragments from the glass case and surrounding windows.

The British Museum collaborated with the AUB to restore eight of these vessels, which you can see on free display from 25 August to 23 October. Find out more about the project and the vessels' history.

Here's how the teams from this collaborative partnership restored the vessels over three months...

Stage one – sorting the pieces

After the blast, Conservator Claire Cuyaubère and the rest of the AUB museum team documented the broken fragments in situ using an archaeological grid system, which preserved connections between shards as well as their location on the gallery floor. At the same time, the team started to link fragments and stabilise the deteriorated glass surfaces by using a conservation material called Paraloid B72. In the form of small acrylic beads, Paraloid B72 can be dissolved in acetone or alcohol to create a solution which is applied to the fragile surfaces to strengthen them. This initial recovery process was vital as it enabled us to understand how many of these vessels were 'reconstructable' and could became part of Shattered glass of Beirut.

Stage two – the vessels arrive in London

From the shards, Claire identified eight vessels – ranging from the first to the ninth century – that were able to be reconstructed and could travel to London safely. Once the vessels arrived in London, Claire joined the British Museum team as the Project Conservator and laid out the fragments in the Weston Archaeology Room in the World Conservation and Exhibition Centre (WCEC). Somewhat hidden behind the Museum, the WCEC provides state-of-the-art laboratories and studios for conservation and scientific research and world-class collection stores. We agreed to divide the vessels into three tiers in relation to the number of fragments they were shattered into and the difficulty of reconstruction. Tier 1 objects were the smallest in size and easiest to reconstruct. Tier 2 and tier 3 objects were more complicated and had some decoration.

Stage three – beginning the restoration

Claire started with the Tier 1 objects. Before each reconstruction, Claire, who was already very familiar with the vessels, carried out additional puzzle work to make sure that she did not miss out any fragments for each individual vessel. This was a painstaking process. It was also important to clean the edges and surfaces with a 50/50 alcohol and deionised water solution to remove all the dirt, grease and previously applied conservation adhesives before the fragments could be dry reconstructed, first with Scotch tape. Dry reconstruction helps us see how well the fragments join together, as well as enabling us to gauge the number of missing fragments. However, we could only tape the fragments when the surfaces didn't contain any archaeological deposits or layers of deteriorated 'iridescence' (where the surface of the glass has a rainbow-like effect).

At the final stage, the fragments were adhered with a conservation adhesive. This part is particularly challenging. When glass breaks, original shapes and internal tensions that occur during manufacturing become severely affected. This means that when conservators reconstruct glass objects, internal tensions change, and the fragments may resist joining each other as they did in its original form. This is called 'springing'. The conservator needs to be extremely focused to achieve the best joins against all the stresses which glass fragments may present. Once this challenge is completed and the conservator is happy, then the objects are left for the adhesive to fully set before they can be handled again.

Final stage – resin fills

The final stage of conservation was to create resin fills, new pieces that will support some of the missing areas on each vessel for the future protection of the objects. This work involved evaluation and discussions about using individual resins and how to prepare them accordingly for the different areas to be filled. We decided to use Paraloid B72, a commonly used acrylic resin in conservation, both as an adhesive and for the fill material. We traced the shapes of areas to be filled onto plastic Melinex® sheets, then transferred these shapes onto specially prepared resin sheets before cutting them out. This method helped us create fills which would perfectly fit into the gaps. Finally, the fills were very lightly tinted using acrylic and watercolour paints to make it possible to see the fill rather than hide the repair. Since Paraloid B72 resin dissolves and is activated (becomes sticky) in Acetone, the fills were attached onto the missing areas by gently softening the edges of fills with Acetone.

New discoveries

As the conservation work on these eight vessels continued, scientific analysis was carried out on individual glass fragments, by colleagues from the Scientific Research Department at the British Museum and University College of London's Institute of Archaeology, providing significant information about the provenance of glass production, the nature of glass materials and some interesting manufacturing details. Using non-destructive scanning techniques, so as not to damage the objects or disrupt the conservation work, the team determined that the vessels were made at sites along the eastern Mediterranean coast, and that some vessels showed signs of recycling in their production, with craftspeople possibly using older glass to make new objects.

The conservation part of the project was completed on 8 July with eight glass vessels returning to life after the devastation they had been through. To date, 26 glass vessels have been conserved in total (18 at the AUB Museum and eight at the British Museum), leaving 46 glass objects to be conserved in the near future. This ongoing project gives us great courage that, even in the wake of such destruction, there is hope… there is always hope.

You can see the restored vessels in The Asahi Shimbun Displays Shattered glass of Beirut in Room 3 from 25 August to 23 October 2022. The British Museum is grateful to the following for their support of the project: TEFAF Museum Restoration Fund, HENI, The Radcliffe Trust, The Charlotte Bonham-Carter Charitable Trust, The Leche Trust, The Thriplow Charitable Trust, Friends of the Middle East Department, The Wakefield Trust and Middle East Airlines.