Abstract
The importance of plastic materials has grown exponentially over the last two centuries and today many ethnographic, historical and artistic collections include a significant number of pieces made with these molding materials. Its origin dates back to ancient times, when the first natural plastics were used; This group includes natural rubber, horn, shellac, bois durci, linoleum or papier-mâché, and bituminous plastics. The first semi-synthetic plastics were obtained by chance as early as the 19th century and include materials such as vulcanized rubber, cellulose nitrate and acetate, and casein plastics. Already throughout the 20th century, synthetic plastics appeared, of great importance at an industrial level, such as PVC, PMMA or polyethylene.
Even today, the conservation problems they pose are not always well known to conservators-restorers. These include cracking, descohesion and dustiness, changes in color, deformation, deposits of sticky exudates and the release of vapors. The presence of some additives (mainly plasticizers) together with the action of temperature and light are some of the agents that cause these damages, most of them being irreversible. Each type of plastic requires certain storage and exposure conditions, so it is essential to know the composition of the piece as accurately as possible to adapt the necessary preventive conservation strategies.