Conservation and restoration of plastic objects
Conservation and restoration of objects made from plastics is work dedicated to the conservation of objects of historical and personal value made from plastics. When applied to cultural heritage, this activity is generally undertaken by a conservator-restorer. Background. Within museum collections, there are a variety of artworks and artifacts that are composed of organic plastic materials, either synthetic or semi-synthetic; these were created for a range of uses from artistic, to technical, to domestic use. Plastics have become an integral component of life, and many plastic artifacts have become cultural icons or  objects worth preserving for the future. Although relatively new materials for museum collections, having originated in the 19th century, plastics are deteriorating at an alarming rate. This risks the loss not only of the objects themselves, but other nearby materials may also be degraded by outgassing or reactions with other released chemicals. Identification of plastics. Identification of plastic components of a collection is extremely important, because some plastics may release a harmful toxin or gas that can damage nearby objects. A preservation plan can be established to slow down the effects and protect a collection. Plastics are identified by various  methods, including trade name, trademark, or patent number. Depending on the manufacturer, different chemical formulas and materials may have been used to produce the plastic over the years. A recycling code may be present, giving general information about the material composition. Plastic composites or proprietary blends can be more difficult to identify. If there are no markings to identify the type of plastic used, it may still be identified by using various types of spectroscopic technology such as optical spectrometer, Raman mid-infrared spectroscopy, and near-infrared spectroscopy, along with mass spectrometry. Other forms of identification include elemental analysis or  thermal analysis to decipher the composition of plastics. The Museum of Design in Plastics (MoDiP), has created a guide to plastic objects that includes the manufacturing dates and manufacturing processes, along with its typical characteristics such as feel and smell. If an object in the collection has characteristics that differ from what is expected, it is possible that the piece has begun to deteriorate. Common plastics. The list below is of chemical compositions that make up common plastics found in museum collections. These are some plastics that may degrade, but are not seriously harmful to nearby objects: The following are  malignant plastic materials that will age rapidly if left untreated, and which have a higher risk of off-gassing or releasing toxic materials that can damage surrounding objects: Environmental concerns have driven recent changes in plastic manufacturing towards biodegradable plastics, with a potentially negative effect upon the long-term stability of such materials within museum collections. Deterioration. A difficult aspect of plastic deterioration is that one cannot see what types of chemical reactions are occurring in the interior of an object, or easily identify the makeup of proprietary plastic composites. Many plastics will give off a distinct odor, ooze  liquids, or will begin to shrink or crack in some way as they age. Although deterioration cannot always be stopped, it is important to know the causes and be able to mitigate or slow damage. Causes. The causes of deterioration regarding plastics can be linked to age, chemical composition, storage, and improper handling of the objects: Chemical processes. Understanding the different types of plastic chemical degradation helps in planning specific measures to protect plastic artifacts. Listed below are types of chemical reactions that accelerate the deterioration of the polymer's structure: Additional effects of deterioration: Plastics composed of cellulose  acetate, when exposed to water, often will give off a smell of vinegar (vinegar syndrome); the surface will have a white powder residue and will begin to shrink. Cellulose acetate butyrate (CAB) and cellulose butyrate will produce butyric acid which has a "vomit odor". Polyvinyl chloride may cause a "blooming" effect, white powder on the surface that can contaminate nearby materials. Preventive care. Safe handling. Impermeable safety gloves such as those made of nitrile can help prevent toxins from entering the skin when handling plastic objects. Dust masks, respirators, or other personal protective equipment may be required for protection from  outgassing or airborne microplastic dusts produced by some decaying plastics. Storage environment. Plastics are best stored with a relative humidity level of 50%, at a storage temperature of , in light-proof enclosures. Because the composition of each plastic material can be different, it is difficult to designate a single uniform storage care plan; understanding the specific composition of a plastic artifact can help determine its preferred climate conditions. Keeping plastics at a stable low temperature and placing these objects either in cold storage or in oxygen-impermeable bags helps to slow degradation. Monitoring plastics in their storage environment is done  by tracking their status and condition by using log entries on spreadsheets or in another database. Monitoring the temperature environment is done using data logger hardware which tracks hourly changes in temperature (and optionally, humidity). Long-term storage supplies. Adsorbents such as activated carbon, silica gel, and zeolites are used to absorb gases that are released from plastics. These absorbents can also be used when the object is on display to prevent and off-gassing that could occur, whether the object is on exhibit or in long-term storage. Absorbents along with acid-free boxes can help slow down the  process of degradation and vinegar syndrome which is common in certain types of film, Lego plastics, and artwork. A yearly checkup of plastic artifacts can help monitor their condition, as well as the condition of the surrounding objects to verify that they have not been cross-contaminated. Objects composed of flammable and unstable cellulose nitrate especially benefit from cold storage, to reduce their rate of decay. Oxygen impermeable bags are used to exclude atmospheric oxygen from the bag. In combination with oxygen absorbers, this prevents oxidation and deterioration of the contents. Conservation. The process of conservation and restoration of plastics  requires an understanding of chemical composition of the material and an appreciation for the possible methods of restoration and their limitations, as well as development of a post-treatment preventive care plan for the object. Cleaning. The process of cleaning plastics is done with the use of appropriate solvents, after identifying the polymers that make up the composition of the plastic. A spot test can be performed if there is uncertainty how the object will react to water or solvents. Scratch removal. Within the field of contemporary art, where the surface finish is part of the artist's intent, the  removal of scratches may need to be more nuanced, compared to simply compensating for accidental damage to social-historical artifacts. Conservators have developed and scientifically investigated a variety of methods for scratch removal. Filling. Fillings may be needed if an object has suffered considerable loss of material due to accidental damage or chemical deterioration. The process of filling depends on the object's chemical composition, and requires consideration of refractive indexes, transparency, viscosity, and its compatibility with the rest of the object.