Attics and Basements and Closets, Oh My! Part 16: Plastics

While those of us in the conservation department grapple with the many challenges facing our society, we are finding comfort in our family heirlooms and treasures—many of which require our attention. We understand that like us, many of you may be turning to your family treasures for comfort during these trying times. Thus, the conservation department would like to share tips on ways to care for your personal collections and assure you that we are here to support you and the collections that you hold dear. 

Each week a different student from the Winterthur/University of Delaware Program in Art Conservation will address ways to care for the collections in your cupboards. This week’s post focuses on the care and storage of plastics and was written by rising second-year Objects Fellow, Abigail Rodriguez.

Caring for Plastics 

What are plastics?

As plastics have become ubiquitous in modern life, it is essential to consider how use, display, and handling can affect their longevity in our personal collections. From vinyl records to resin jewelry, there are plastics everywhere, representing a wide array of art and everyday objects. 

​Plastics are based on polymers. The properties of plastics are based on the structure of the base polymer and the molecular groups attached to the central chain. While there are many ways to categorize plastics, they have been traditionally classified as: natural, semi-synthetic, or synthetic. These classifications are based on the origin of the material, from which the plastic is derived. Examples of natural plastics include tortoiseshell, horn, and gutta percha (a thermoplastic material obtained from trees). Semi-synthetic plastics are made from natural materials that are chemically altered; examples of these plastics include cellulose acetate and cellulose nitrate. Fully synthetic plastics are produced entirely in a laboratory - the first synthetic plastic was Bakelite in 1907!  

Every plastic object has its own unique combination of polymers, additives, and past exposure. This can make caring for plastics a daunting task. The following sections will provide a brief overview of some key causes of damage for plastic objects, signs that your treasures may be in peril, and how to prevent future damage. 

Causes of Damage and Signs of Deterioration

Plastics can deteriorate for a variety of reasons, including overexposure to light, heat, moisture, and some airborne pollutants like ozone. Plastics can also degrade as a result of mechanical stress and inherent vice. 

Plastic deterioration usually presents with some of the following symptoms: 

• Cracking
• Changes in flexibility and/or distortion
• Formation of bloom (a white substance on the surface of the plastic) 
• Weeping (the collection of wet deposits on the surface of the plastic)
• Discoloration
• Embrittlement
• Development of strong odors 
• Surface stickiness
• And, in composite objects, the corrosion of metal components
  

​Some plastics are more vulnerable than others – early semi-synthetic plastics like cellulose acetate and cellulose nitrate tend to breakdown more readily than more modern synthetic plastics like polypropylene. It is important to be able to recognize signs of deterioration as some plastics can emit gases that are harmful to nearby materials. For example, cellulose acetate and cellulose nitrate emit acetic acid and nitric acid, respectively, as they degrade. Because these acids can cause reactions with other objects in the vicinity, it is important to isolate degrading cellulose acetate and cellulose nitrate objects.

Care and Display

Most polymer degradation processes are cyclical and irreversible, making preventive action in the care of plastics very important!  Because plastics are often manufactured to be disposable, they are not chemically designed to endure. Keeping this in mind, it can be a good idea to minimize handling plastics with bare hands and instead use an inert material such as cotton as a barrier layer. This is good practice as long as the surface of the plastic is not sticky.  

If possible, display plastic objects on interior shelves or in shaded areas to keep them from direct light exposure. It is also optimum to keep plastics away from heaters, windows, and any incandescent (or other heat-producing) light sources. Ensuring that the display area has a cool, stable, well-ventilated, and dust-free environment will also help mitigate degradation. For flexible objects, support the natural shape with a mount of non-plastic materials such as acid-free tissue paper, mylar, Ethafoam, or cardboard. This will prevent deformation from occurring down the road.  

If placing a plastic object in storage, always avoid completely sealing the container to allow for ventilation.

Identifying Plastics

If you are curious about the types of plastics in your collection, here are some resources for diving deeper into qualitative identification: 

Plastics Historical Society – The Identification of Plastics: http://plastiquarian.com/?page_id=14327 

Museum of Design in Plastics – Identifying Plastics: https://plastic-en.tool.cultureelerfgoed.nl/ 

Museum of Design in Plastics – Plastics timeline: https://www.modip.ac.uk/projects/curators-guide/plastics-timeline 

National Park Service – Care and Identification of Objects Made from Plastic (2010):  https://www.nps.gov/museum/publications/conserveogram/08-04.pdf 

While most plastics need confirmation with analytical techniques, it can be fun to consider the rich histories plastic objects have come to represent in the 20th and 21st centuries and in your personal collections. 

We hope you are enjoying these entries in our series focused on caring for your family heirlooms. This series will continue throughout the summer and cover a variety of items and materials. If you have any comments on the series thus far, including materials you’d like to see covered in future posts, please email us at art-conservation@udel.edu. The previous posts in this series are available on the Department of Art Conservation website here.

You are in our hearts and minds as collectively we face many challenges. We hope you and your loved ones are safe and healthy. When we emerge from this global crisis we must and will rely on art and culture, preserved for today and for future generations, to foster joy, well-being and hope. We encourage you to visit our web site for regular updates on our department of art conservation and news coverage of our treasured students and alumni at home and abroad.