Plastic Fantastic?! Conservation of Modern Objects in the HIV/AIDS Collections

This week our project conservator, Emily Hick, discusses the problems with plastics in archival collections:

Over the past five weeks I have been working on one part of the HIV/AIDS collections which documents the ‘Take Care’ Campaign in Edinburgh and the Lothians. This campaign began in the late 1980s and aimed to raise awareness among all members of the community about the causes of HIV/AIDS and also to promote safer sex with the message “take care of the one you love”. This was achieved through high profile events and gigs, as well as educational programmes and providing free sexual health advice and condoms. This diverse collection contains a wide range of materials; from modern paper materials such as reports, educational packs and administrative files to plastic audio visual objects and modern rubber/latex items such as balloons and condoms.

Many people assume that modern collections such as this do not require conservation, however this is not the case, and there are already items in this collection that are severely degraded. For example, balloon 1 in the photograph below has degraded and become extremely brittle, resulting in it becoming fragmented when flexed during storage. The conservation of modern plastic materials is complex as although the objects may look similar, they may not be formed of the same materials and depending on the original composition of the plastic object, it can degrade in different ways. For example, these four balloons (1 – 4) were stored together in the same environment, but have degraded in completely different ways. Balloon 1 has become brittle and fragmented, balloon 2 has become tacky and stuck to a business card it was stored with, balloon 3 has hardened and balloon 4 is still relatively flexible.

Four balloons stored in the same environment that have degraded in different ways

 

Deterioration of plastics such as this can be caused by either chemical or physical factors. Chemical degradation can be caused by the interaction of plastics with light, heat, oxygen or water. These factors provide the energy and the environment to promote destructive chemical processes. Physical factors include degradation caused handling of the object, for example the incorrect handling and repeated bending of a plastic doll may result in stress fractures or breakages. Physical degradation can also be caused by the migration of additives from the plastic object. Plastics contain additives called plasticizers that increase the flexibility of the object. However as the object ages, the plasticizers evaporate causing it to become more brittle, which has occured in balloon 1. This can be particularly problematic if the plasticizers are absorbed by another material in close contact with the object. The photograph below shows a window sticker that has degraded, releasing plasticizers which have in turn been absorbed by the plastic pocket it was previously stored in, resulting in deformation of the pocket.  

Plasticizers released by the window sticker have been absorbed by the plastic pocket causing it to deform

Plastics objects not only form part of this collection, but plastics such as ring binders and poly-pockets are also used to store many paper materials. These materials also degrade and can adversely affect the papers contained within them. Store-bought ring binders can be especially problematic for archival collections as they are commonly formed from PVC (polyvinylchloride). This type of plastic emits hydrochloric acid over time which can be readily absorbed by paper materials and cause them to degrade. As such all paper materials have been removed from these folders, but reference samples have been kept separately so that the original look and function of the materials can be recreated if necessary.

The conservation of the plastic items in the collections has particularly caught my interest as this is a subject area that I had little prior knowledge of and did not expect to be treating when I qualified as a paper conservator! The production of plastics has risen dramatically over the past 50 years, from 5 million tonnes in the 1950s to almost 100 million tonnes in early 2000. In 1982, the production of plastic surpassed that of steel and as such that year has been dubbed the beginning of the ‘Plastic Age’. Therefore, the amount of plastics found in archives is growing and although research about this subject matter is relatively small, it is a fascinating area, and I believe that the issues surrounding the conservation of this material will become more important in the future.