philco dial_SW

Unstable Plastics: Preservation Challenges in Museum Collections

Plastics are so much a part of our lives that we don’t even think about them except when we check for the recyclable symbol. Plastics in museums (Figure 1), however, deserve much more attention as they present significant and constant collecting and preservation challenges.

Figure 1. The Temperature Control (TC) room in one of the Canada Science and Technology Museums Corporation storage facilities provides constant and cool storage conditions for many small objects made of early plastics.

Figure 1. The Temperature Control (TC) room in one of the Canada Science and Technology Museums Corporation storage facilities provides constant and cool storage conditions for many small objects made of early plastics.

The first synthetic plastic was patented in 1865, meaning that plastics are 150 years old this year. We collect plastic artifacts not as examples of the plastics themselves, but as part of a collection of technological and social history objects significant to Canadians (Figure 2). One of the earliest plastics was rubber, and it is not hard to imagine the amount of rubber in a collection of technological history….. tires, tubes, gaskets, seals, floor mats, fabrics, wires, elastics….everywhere.

Figure 1. (A) Embrittlement caused by degraded cellulose acetate is clearly visible in this car knob from a 1948 Chrysler Town and Country car. (B) The degraded cellulose nitrate is visible on the mouthpiece of this tobacco pipe. (C) Degraded ebonite on a 19th century stethoscope. (D) Signs of degradation due to exposure to oxygen and light, on the rubber of this WW1 gas mask.

Figure 2. (A) Embrittlement caused by degraded cellulose acetate is clearly visible in this car knob from a 1948 Chrysler Town and Country car. (B) The degraded cellulose nitrate is visible on the mouthpiece of this tobacco pipe. (C) Degraded ebonite on a 19th century stethoscope. (D) Signs of degradation due to exposure to oxygen and light, on the rubber of this WW1 gas mask.

 

The preservation of plastics is a growing concern in the field of Conservation due to the instability of some types. There is much study being done in Europe, mostly related to plastic in works of art and decorative objects. PoPArt, the Preservation Of Plastic ARTefacts in museum collections is a good example. There is far less being done for plastics in collections of technology, which is worrying for us. The Canadian Association for Conservation of Cultural Property sponsored a workshop in 2010, that brought together some of Canada’s leading experts including Scott Williams and Julia Fenn. This workshop focused on plastics in the collection of the Canada Science and Technology Museum Corporation.

 

“The preservation of plastics is a growing concern in the field of Conservation due to the instability of some types”.

Why do we worry about plastics in our collection? Because we find them everywhere. They were arguably the material that most affected the electrification of the world: allowing for the production of cables (transatlantic cable 1854 to 1858, and again 1865-66), insulating materials, and moulded shapes for consumer products such as telephone receivers (Figure 3). In our transportation collection, we have plenty of rubber tires, and we also find plastic steering wheels, knobs, safety glass (which has a plastic layer sandwiched between glass), moulded dash and interior panels and fittings, and vinyl upholstery.   Aircraft contain a similar range of plastics materials; it being one of the great technological advancements between World War I and II that allowed for the huge innovations in aircraft construction between the Wars. From a design perspective, plastics, and the ability to mould complex shapes; permitted the creation of iconic decorative objects from the 20th Century, including radios, lamps, telephones, furniture and fashion accessories.

 

Figure 2. (A) The moulded shapes and colour effects of urea formaldehyde plastic are clearly visible on this Philco rotary dial. (B) A sample of an early marine telegraph cable, made of gutta percha, which is actually remarkably stable.

Figure 3. (A) The moulded shapes and colour effects of urea formaldehyde plastic are clearly visible on this Philco rotary dial. (B) A sample of an early marine telegraph cable, made of gutta percha, which is actually remarkably stable.

 

“Plastics are a fascinating class of material; and we owe a great deal to the early pioneers of chemistry,  whose achievements have allowed for the ubiquitous presence of this material in our lives today”.

 

There are some plastics that we know won’t last, such as rubber and PVC; but we do have strategies for prolonging their life expectancy. Some need to be stored in the dark, some in cold temperatures, and some in an oxygen-free environment. Some need all three. Private collectors should be aware of the type of plastic they have, so that they can care for it properly. Bakelite is one of the most stable plastics, and fortunately the majority of decorative items to be found at Antiques sales, are of this material.   Cellulose nitrate, on the other hand, also used to make decorative items; is inherently unstable.   Collectors should know this and take special care of it.

 

Figure 4.

Figure 4. Embrittlement

 

 

What does plastic deterioration look like? It can take the form of embrittlement (Figure 4), surface changes, stickiness, or a change of colour. Some (like cellulose nitrate) release an invisible gas which in the presence of moisture, can form acid on adjacent surfaces. This will cause organics to disintegrate, and metals to corrode. Cellulose nitrate buttons on an old gown, for instance, will eventually result in holes in the fabric, and corrosion of any metal decoration or button shanks. They should therefore be removed and stored separately, even if it breaks your heart to do so.

 

 

 

 

 

 

 

The Conservation and Collection Services Division is responsible for the long-term care, preservation, and housing of the National Collection for the Canada Science and Technology Museums Corporation.

 

 

 

 

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