Conserving a painted rickshaw
In 1987 The British Museum acquired a rickshaw, and a collection of painted motifs from rickshaws, from Bangladesh. These colourful artefacts are interesting for the conservator as they are made from modern plastics. Discs of polyvinyl chloride (PVC) are painted with designs in oil-based paints, which are then attached to the colourful tricycles. Some of these motifs are covered with slips of clear sticky-backed plastic, which is thought to be a PVC film with a polyvinyl acetate (PVAc) adhesive layer.
PVC is unstable: it tends to shrink and distort on aging and causes the painted decoration to flake or peel away; the surface becomes sticky as the plasticizer within the material breaks down and the paint colour leaches into the plastic below. The sticky-backed plastic cover-slips are also a problem: the PVAc loses its stickiness over time and contributes to the causes of flaking and deterioration.
The conservation of modern plastics is a new field. Research is in progress to find methods to stop the deterioration of the materials. In this example the painted designs on the rickshaw were secured to the plastic base with a PVAc adhesive. Silicone release film, which neither sticks to adhesive nor creates static electricity, was placed above and below the decorations. Finally, the decorations were mounted in acid-free card window mounts. As can be seen, the more recent acquisitions in the Museum are no less vulnerable for being modern.