Examination and experimentation: conservation of an archaeological glass unguentarium for display

SOURCE: https://www.britishmuseum.org/pdf/BMTRB_7_Barton_Meek_and_Roberts.pdf

SUMMARYA Roman unguentarium (No.1851,0813.493) excavated in Apt, France was assessed during a conservation survey of the glass reserve collection of the Department of Greece and Rome at the British Museum. On examination the unguentarium was highlighted as a very unusual example, because of its size, shape, colour and decoration. It was therefore decided to place it on permanent display and a complex programme of conservation and investigation was instigated.Before conservation, the lower section of the object was covered in a dense gap fill that was fracturing and obscuring the fragile glass. X-radiography showed a complete profile under the fill, which enabled the object to be dismantled and reassembled; the missing areas were then filled for stability and display. Examination and scientific analysis using optical microscopy, scanning electron microscopy with energy dispersive X-ray spectrometry and Raman spectroscopy helped to identify materials and inform the conservation project. When the unusual, historic fill was analysed to aid its removal it was found to contain large quantities of mica and lead; the poisonous nature of the lead meant that the unguentarium had to be dismantled under carefully controlled conditions. In addition to reassembling the glass elements of the vessel, large gap fills were needed to integrate the remaining fragments and to support the relatively intact upper part of the vessel. After reviewing the gap-filling methods available and conducting experiments with materials and techniques, a procedure was developed that involved: moulding and modelling the missing areas using polyester paste; creating a two-part mould of the polyester fragment; casting a translucent, tinted epoxy gap fill from the mould; and reassembly of the vessel fragme

Authors:

Julia Barton (jbarton@thebritishmuseum.ac.uk) is a ceramics and glass conservator and Andrew Meek (ameek@thebritishmuseum.ac.uk) a sci-entist, both in the Department of Conservation and Scientific Research. Paul Roberts (proberts@thebritishmuseum.ac.uk) is a curator in the Department of Greece and Rome at the British Museum