Plastics 205
processes. Exposure to moisture, heat and light leads to polyurethanes’ degrad-
ation by hydrolysis. Degradation results in chain scission, in which energy
breaks polymer chain bonds to create a polymer with two or more shorter
chains, manifested by crumbling of foams. Such crumbling often starts at
surface skins of foams and, when the surfaces crumble and fall way from the
object, fresh, undegraded foam is exposed to light and oxygen, perpetuating
degradation to the point of complete failure.
5 Conservation of Plastics
In 1993, a committee of curators and conservators, representing six major
museums of modern and contemporary art in the Netherlands concluded that:
●there were no generally accepted methods and criteria for solving the
conservation problems of non-traditional objects and modern art;
●there was little insight into the nature and use of modern materials; and
●knowledge concerning the composition and ageing of modern materials
was difficult to access.Deterioration of plastic objects in museums has only been recognised as an
important area worthy of research since 1991, while the scope of the prob-
lems surrounding the preservation of modern art has only been appreciated
internationally as recently as 1998. Little is known about the conservation of
plastics compared to other materials found in museums. To date, few conser-
vation practices have been established, and development of new treatments is
far slower than most degradation processes. Once deterioration has started, it
cannot be stopped or reversed, but only slowed.
Conservators consider two approaches to conservation when planning treat-
ment for any degraded object; activealso known as interventive, and preventive
also known as passive. Active conservation treatments are those involving prac-
tical treatments applied as necessary to individual objects to limit further deteri-
oration. They include adhering broken sections, cleaning surfaces and filling
missing areas to strengthen the objects weakened by deterioration. Although
most condition surveys of objects containing plastics conclude that approxi-
mately 75% of collections require cleaning, such active conservation practices
are still poorly developed. The major cause is the sensitivity of many plastics to
organic liquids, aqueous solutions and water itself, particularly if the polymer
has deteriorated. Any coating or adhesive that adheres successfully to a plastic
surface, must either soften or melt the substrate. This process changes the
appearance of the original, which may not be acceptable for works of art. Since
this area is so poorly developed and appropriate treatments need to be almost
customised to suit individual objects, it will not be discussed further here.