Conservation and restoration of plastic objects
Conservation and restoration of objects made from plastics is work dedicated to the
Background
Within museum collections, there are a variety of artworks and artifacts that are composed of organic plastic materials, either
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.[3][4]
Plastics are identified by various methods, including trade name,
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,[4] and near-infrared spectroscopy, along with mass spectrometry.[3] Other forms of identification include elemental analysis or thermal analysis to decipher the composition of plastics.[3]
The
In 2022, the Getty Conservation Institute published a book on the properties of commonly-used plastics and elastomers, including 56 "fact sheets" summarizing important characteristics of the materials, and methods of identification.[6]
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:
- Non-plasticized (rigid) polyvinyl chloride (PVC)[7]
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:[3]
- Polyvinyl chloride treated with plasticizers[8][7]
- Polyurethane
- Cellulose esters, including
- Vulcanized rubber
- Biodegradable plastics
Environmental concerns have driven recent changes in plastic manufacturing towards biodegradable plastics,[10] with a potentially negative effect upon the long-term stability of such materials within museum collections.[11][8]
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.[12] 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:
- Age – When plastics were first manufactured in the 19th century, they were derived directly from organic materials; over the years these objects have usually deteriorated due to lack of knowledge and improper handling of the early plastics.[1]
- Chemical – Depending on an object's chemical composition, conservators can understand how it will react over time. Other chemical reactions are driven by heat, oxygen, light, liquids, additives, and biological attacks.[13]
- Storage – Improper storage of plastic artifacts can allow contamination and deterioration to occur. This often occurs when temperature or relative humidity fluctuate in the storage area, and this may cause the polymers to react to the environment, to deteriorate, and possibly to contaminate surrounding objects. Maintaining stable storage conditions is also important when an object is on exhibit. When the object is lighted and on display, its temperature and humidity can fluctuate. Conditions inside the exhibit case must be monitored and adjusted when necessary, to help prevent any damage.[1]
- Improper handling – Improper cleaning techniques when using water or solvents on incompatible materials can cause damage.[1] Also, human error when handling objects can occur, causing abrasions or scratches.
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:
- Photo-oxidative degradation occurs when plastic degrades from exposure to ultraviolet (UV) or visible light; the most damaging wavelengths depend on the composition of the polymer.[14]In general, plastic will be affected by light, and it is best practice to keep plastic away from light sources as much as possible, especially during longterm storage.
- Thermal degradation affects the entire bulk volume of the polymer making up an object, and is strongly affected by the temperature and amount of light exposure.[14]
- Ozone-induced degradation will deteriorate saturated and unsaturated polymers when the plastic is exposed to atmospheric ozone.[14] A test can be conducted to see if the object has been exposed, by taking small samples for analysis using Fourier-transform infrared spectroscopy (FTIR).[14]
- plastic waste polymers as they are transformed into hydrocarbons.[clarification needed]
- Biodegradation causes the surface or the strength of the plastic to change; this process eventually decomposes vulnerable materials into carbon dioxide and water as microbes consume components of the material.[14]
- Hydroperoxide decomposition occurs when metal and metal ions within the plastic material lead to the deterioration of the object[13]
- carcinogenicin their biological effects.
Plastic | UV radiation and excess light (photolysis, photo-oxidation) | Moisture (high relative humidity) and moisture fluctuations (hydrolysis, swelling, shrinkage) | Pollutants | Effects on other nearby materials (stains, corrosion, stickiness, gases) |
---|---|---|---|---|
Acrylics | resistant | resistant | dissolved, swelled, stress, cracking | none |
Casein-formaldehyde , protein derivatives
|
formaldehyde gas, cracking due to swelling/shrinking, moldy appearance, brittle when dry | swell by water, resistant to organics | formaldehyde, hydrogen sulfide, other sulfur-containing gases | |
Cellulose acetate | yellowed, brittle | hydrolysis produces acetic acid oily plasticized liquids. White powder residue may also be visible[15] | dissolved swelled | acetic acid gas, oily plasticizer and degradation products on surface |
Cellulose nitrate
|
yellowed, brittle | hydrolysis produces acidic and oxidizing nitrogen oxide gases | dissolved, swelled | acidic and oxidizing nitrogen oxide gases, plasticizer, and degradation products on surface; material is explosively flammable
|
Nylon (polyamide) | yellowed, brittle | potential hydrolysis at extreme conditions | softened, swelled | none |
Phenolics
( phenol formaldehyde )
|
discolored and more matte | discolored and more matte | fillers swell and surface mottles with solvents | phenol and formaldehyde with severe degradation |
Polyolefin
(polyethylene, polypropylene) |
yellowed, brittle | resistant | swollen by some organics | none |
Polystyrene | yellowed, brittled | resistant | dissolved, swelled, stress cracked | none |
Polyurethane | yellowed, brittle, sticky, crumbles | yellowed, brittle, sticky, crumbles | swelled, stress cracked | nitrogenous organic gases and liquids |
Polyvinyl chloride | yellowed, brittle | resistant | dissolved, swelled, embrittled by plasticizer extraction | oily plasticizer liquids, maybe hydrochloric acid gas under extreme conditions of moisture and light exposure |
Rubber, ebonite, vulcanite | brittle, discolored, increase in matteness | hydrogen sulfide and other gases, sulfuric acid on surfaces | surface mottled by solvents | hydrogen sulfide and other sulfur-containing gases, sulfuric acid on surfaces |
All plastics (and organics) | should be considered as prone to damage by ultraviolet radiation usually resulting in yellowing and embrittlement | condensation plastics like esters, amides, and urethanes are subject to hydrolysis with subsequent weakening | thermoplastics may dissolve, thermosets may swell, stress cracking | harmful gases from plastics with chlorine, sulfur, and pendant (not main chain) ester groups |
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.[15]
Cellulose acetate butyrate (CAB) and cellulose butyrate will produce butyric acid which has a "vomit odor".[3][16]
Polyvinyl chloride may cause a "blooming" effect, white powder on the surface that can contaminate nearby materials.[3]
Preventive care
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.[17]
Safe handling
Impermeable safety gloves such as those made of
Storage environment
Plastics are best stored with a
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). Objects composed of flammable and unstable
Long-term storage supplies
Oxygen-impermeable bags are used to exclude atmospheric oxygen. In combination with oxygen absorbers, this prevents
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.[18] 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.[19]
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.[20]
See also
References
- ^ a b c d e f "Care and Identification of Objects Made from Plastic" (PDF). Conserve O Gram. 2010 – via National Park Service.
- PMID 19528049.
- ^ a b c d e f g h Williams, Scott (2002). "Care of Plastics: Malignant Plastics". WAAC Newsletter. 24 – via COOL Database.
- ^ hdl:10362/117046.
- ^ "A - Z of plastics materials". Museum of Design in Plastics (MoDiP). Archived from the original on 2018-03-25. Retrieved 2018-04-08.
- ISBN 978-1-60606-693-5.
- ^ a b Staff, Creative Mechanisms. "Everything You Need To Know About PVC Plastic". Retrieved 2018-04-04.
- ^ a b c "Preserving Plastics: An Evolving Material a Maturing Profession (Feature)". www.getty.edu. Retrieved 2018-03-31.
- ^ "Preservation of Plastics". www.getty.edu. Getty Conservation Institute. Retrieved 2022-09-18.
- ^ "What You Can Do to Keep Plastic out of the Ocean". response.restoration.noaa.gov. Retrieved 2018-04-07.
- ^ Madden, Odile (Spring 2014). "Preserving Plastics: An Evolving Material, a Maturing Profession spring 2014. Conservation of plastics" (PDF). Conservation Perspectives the GCI Newsletter: 4–9 – via The Getty Conservation Institute.
- ^ "Identification of plastics by looking, touching and smelling". Blog. Retrieved 2018-04-08.
- ^ a b "Physical and Chemical processes leading to deterioration of original properties of plastic" (PDF). Processes Leading to the Deterioration of Plastics. 2012 – via POPART.
- ^ .
- ^ a b "Care of plastics | Museum of Design in Plastics, MoDiP". www.modip.ac.uk. Archived from the original on 2018-06-10. Retrieved 2018-04-07.
- ^ Alberge, Dalya (18 May 2015). "V&A conservators race to preserve art and design classics in plastic". The Guardian. Retrieved 2021-09-13.
- ^ a b c d e Shashoua, Yvonne (2014). "A Safe Space Storage Strategies for Plastics". Conservation Perspectives. Vol. 29.
- ^ Shashoua, Yvonne (2012). Studies in Active Conservation of Plastic Artefacts in Museums (PDF). POPART. p. 222.
- ^ Laganà, Ana; Rivenc, Rachel; Langenbacher, Julia; Griswold, John; Learner, Tom (2014). "Looking through Plastics: Investigating options for the treatment of scratches, abrasions, and losses in cast unsaturated polyester works of art" (PDF). ICOM-CC 17th Triennial Conference Preprints.
- ^ "The use of lasers in the conservation of museum objects made from plastics". Blog. Retrieved 2018-03-31.
Further reading
- Oosten, Thea van (2022). Properties of plastics : a guide for conservators. Los Angeles: Getty Publications. ISBN 978-1-60606-693-5.
- Shashoua, Yvonne (2012) [2008]. Conservation of Plastics. Routledge. ISBN 978-1-136-41515-9.
- Keneghan, Brenda; Betts, Louise; Egan, Louise, eds. (2008). Plastics: Looking at the Future and Learning from the Past: Papers from the Conference Held at the Victoria and Albert Museum, London, 23-25 May 2007. Archetype. ISBN 978-1-904982-43-2.
- Quye, Anita; Williamson, Colin (November 2005). Plastics: Collecting and Conserving. DIANE Publishing. ISBN 978-0-7567-9729-4.
- Shashoua, Y.; Ward, C. (1995). "Plastics: Modern Resins with Ageing Problems". In Wright, Margot M. (ed.). Resins Ancient and Modern: Pre-prints of the SSCR's 2nd Conference Held at the Department of Zoology, University of Aberdeen, 13-14 September 1995. Scottish Society for Conservation & Restoration. pp. 33–37. ISBN 978-0-9526415-0-6.
- Shashoua, Y. (1996). "A Passive Approach to the Conservation of Polyvinyl Chloride". ICOM Committee for Conservation. 11th Triennial Meeting, Edinburgh, Scotland, 1-6 September 1996: Preprints. James & James. pp. 961–6. ISBN 978-1-873936-50-4.
- Winsor, P. (September 1999). "Conservation of Plastics Collections". MGC Fact Sheets. London: Museums and Galleries Commission.
- Young, L.; Young, A. (2001). "The Preservation, Storage and Display of Spacesuits". Collections Care Report. 5. Washington, DC: Smithsonian National Air and Space Museum.
- Blank, Sharon (1990). "An introduction to plastics and rubbers in collections". Studies in Conservation. 35 (2): 53–63. .
- Martuscelli, E. (2010). The chemistry of degradation and conservation of plastic artefacts. Paideia Firenze. ISBN 978-88-87410-48-8.
- Martuscelli, Ezio (2012). Degradation and preservation of artefacts in synthetic plastics. Paideia. ISBN 978-88-87410-51-8.
External links
- POPART: an international collaborative research project about the preservation of plastic artefacts in museums
- Conservation of plastics
- Safe Handling of Plastics in a Museum Environment
- Deutsches Kunsstoff Museum
- PlArt museo
- Conservation of rubber
- THE CONSERVATION OF A PLASTIC MASK BY MARISOL
- Care of plastics:Malignant Plastics
- Care of Objects Made from Rubber and Plastic
- MoDiP
- The Getty Conservation Institute