Selection of plastic objects tested with the diphenylamine and Molisch spot tests (identify cellulose nitrate and cellulose acetate).

Seminar taught by Lara Kaplan, Objects Conservator in private practice and Affiliated Assistant Professor at Winterthur/University of Delaware Program in Art Conservation (WUDPAC). 

The seminar included a brief history of plastics, common means of deterioration, general preventive recommendations for storage, and research into interventive treatments. The second half of the seminar included lab time for identifying plastics using microchemical spot tests.

Conservators have been actively studying plastics since the early 1990s. According to Yvonne Shashoua, research into the conservation of plastics has occurred in three mesocycles: degradation, preventive conservation, and interventive conservation. The seminar thus covered these three major areas of research.

Plastics can be identified by their degradation. For example, a vinegar scent can indicate that an object is made from cellulose acetate. Signs of deterioration should be considered within the context of the object – e.g. its date and probable means of manufacture.

This plastic shoe tested positive for chlorides using the Beilstein test, indicating that it is PVC.

As with most artifacts, proper environmental conditions can slow rates of deterioration. After identifying the plastic, storage recommendations can be made that address the primary causes of degradation. Generally, darkness, lower temperatures, and steady relative humidity will help to reduce rates of photooxidation and hydrolysis. Ventilation may be appropriate depending on the type of plastic.

Proactive conservation measures are necessary for the preservation of plastic artifacts. Increasingly, there is a desire for interventive treatment options for plastics. The seminar covered cleaning basics and what factors should be considered when approaching any treatment (even dusting!).

There is much more research needed for care of plastics – sustainability, philosophy, interventive treatments, etc. Hopefully, those who are working in the field will continue to publish and share information on what works, and what doesn’t work!

Attempting the Beilstein test to identify PVC. Image courtesy of Melissa King.

I’m excited to be treating two objects with plastic components as a second year Objects fellow: a pair of Christian Dior patent leather heels and an animation cel.

Natalya Swanson