In this blog MOLA Conservator, Luisa Duarte, reveals the meticulous work that went into conserving a beautiful blue glass vessel. The sprinkler was photographed on location by acclaimed photographer Simon Norfolk for a feature on London’s archaeology that appears in the February 2016 edition of National Geographic magazine.
This object was found in the late 90s at Plantation Place in the City and was identified by our finds specialists as an Islamic glass sprinkler. These vessels were most commonly used in rituals to carry perfumes and rose water. We believe that this one was produced in the Levant in the 13th or 14th centuries. The slim neck and bulbous body would have restricted the evaporation and pouring of expensive liquids.
Most of these sprinklers, and ours is no exception, were blown freehand by expert medieval glassmakers. In this case, the manufacturing technique can be easily ascertained though visual examination (see picture above). Firstly the glass is extremely thin, something that can only be achieved through glass blowing; and secondly the base of our sprinkler has a tell-tale scar produced by a pontil, a long iron rod used to shape blown glass.
This fragile object needed to be made stable and strong enough to be transported to the location of the National Geographic photoshoot and to be handled by an expert conservator (me). The nature of the object produced several challenges. The extreme thinness of the glass was one of my main concerns whilst reconstructing this vessel. Other concerns were: the several large areas of loss and the minuteness of some of the fragments.
Additionally, the surface of the glass was quite tricky. The iridescence visible on the surface of the glass, although very beautiful, is not a product of manufacture. This multi-coloured layer was produced by the deterioration of the glass due to hundreds of years of burial. This deterioration layer is very thin and prone to detaching from the undamaged glass core. Although the appearance of this layer is not original, it does represent the actual surface of the object, therefore, it is extremely important to preserve it intact as much as possible.
This created a further challenge when conserving the glass sprinkler, as the first step to reconstructing the vessel was to do a dry-run with adhesive tape. A dry run involves working out where each fragment goes prior to adhering them, this informs conservators of any potential problems before the main build (such as areas of particular fragility or difficulty) and ensures that no fragments will be ‘locked out’ (i.e cannot be fitted) as the build progresses.
In this case I used a tape with low adhesive properties that could easily be removed by applying a weak solvent without dislodging the fragile iridescent layer. The image above shows the use of the tape to place several of the 40+ fragments that comprised the sprinkler prior to sticking them together with a conservation grade adhesive.
The large gaps in the vessel increase the fragility of the object during handling. To solve this issue I supported certain areas of the sprinkler with nylon gossamer. By tinting this fine non-woven textile to the appropriate shade of blue, I created very thin, translucent and strong sheets that were adhered on the internal surface of the weak areas to provide extra structural strength.
You can see the result of my hard work in all its glory in the February 2016 edition of National Geographic magazine, which is also available online.
