Things look bad for Larry the Lamb, retired star of the Thames Television series, Larry the Lamb in Toytown. His polyurethane foam body is disintegrating and there is not a lot his minders at the Victoria and Albert Museum in London can do about it.
Not that they aren't trying. The V&A, one of the largest museums of art and design in the world, has a conservation department with a research group whose role is to find ways to conserve the displays and limit the damage caused by age.
Dr Brenda Keneghan, from Dublin, is a polymer scientist working at the V&A who specialises in the preservation of plastics, a category of materials that is enormously wide and varied, from Bakelite and polyurethane to PVC and blown foams. It is also a very tricky category, Dr Keneghan says, because plastics were generally viewed as a transient substance to be used for a time and then thrown away.
"We are actually fighting against the tide," admits Dr Keneghan. "Plastics tend to degrade chemically, so what you are doing is trying to understand the chemical process of degradation."
Plastics were an important part of the pop culture of the 1960s and 1970s and many items from this period are on display at the V&A. There are much older objects that contain plastics, however. The earliest plastics, such as cellulose nitrate, came into use in the 1850s and were used to produce cheap imitations of more costly natural materials such as bone, tortoise shell and ivory, Dr Keneghan said.
Items made of stone, metal, wood or bone will age but only very slowly and their chemical make-up usually doesn't contribute so dramatically or quickly to their decay. The same cannot be said for plastics, which contain active chemicals such as plasticisers. The plastics themselves also continue to react with the air, humidity and light to reassemble themselves into different chemical structures.
Plastics come in many varieties but a common theme is their polymer chains. This chain structure makes them light, strong and flexible, but over time the chains break down.
"The chain link is usually responsible for the mechanical integrity of the plastic," Dr Keneghan says, and when this goes the plastic degrades.
Such is the difficulty faced by poor Larry the Lamb, the foam puppet that went on the air in 1972. Although still young in human terms, his polyurethane body is breaking down after a short but spectacular career under the bright lights of television.
"Larry is oxidising like mad," Dr Keneghan said. "There is very little we can do. If we don't do anything it will just disappear." Yet this was "the absolute opposite of what we want to happen" in a museum context, she added. Many of these objects, including Larry, were "precious items to children".
The challenge presented by Larry the Lamb is a recurring theme for conservation scientists. How do you protect an object from the ageing process without destroying or completely changing the object you are trying to protect?
The catchword is "reversibility", Dr Keneghan says, meaning the attempt to apply only those techniques that could be reversed in the future should some better, less invasive technology become available. Plastics present a particular problem in this regard.
"Any type of chemical intervention probably isn't reversible," she said, and coatings are almost always out of the question. "We are worried about reversibility and the change in what the object would look like. If you change it, it is not the original object. We are reluctant to pursue things until we really know."
This means that a lot of the work revolves around prevention. Age-related degradation can be reduced in a number of plastics by controlling humidity, exposure to light, temperature and exposure to air, she says. "The most important thing to do is identify the plastic." This is done using infrared spectrometry and a tiny sample that is little more than dust.
Once identified they know from experience what makes it degrade, whether light or humidity or a combination. "Humidity is a very important consideration," she says. "We try to control these parameters."
Controls are usually applied once on display. "Storage is very important because when an object is on view it is about striking a balance between what is good for the visitor and what is good for the object."
Some passive chemical intervention is pursued. Cellulose acetate, for example, changes chemically over time to produce acetic acid, which produces the familiar chip shop vinegar smell. Those attempting to protect old films made of cellulose acetate have experience of the "vinegar syndrome" each time they open an ageing can of film, Dr Keneghan says.
Their response at the V&A is to attempt to mop up the acetic acid in the display case, using a "molecular sieve". This helps to reduce breakdown caused by the acid.
Plastics feature in a surprising range of displays at the museum. The Duke of Wellington's campaign chair is on display and needs treatment because it was coated with cellulose nitrate. There are 1960s air-filled plastic chairs and polyurethane-coated beanbags. There is a pair of Elton John's sunglasses and the stage fans of turn of the century theatre performer, Beatrice Lillie. The ostrich feathers are in fine shape but the cellulose nitrate struts which hold them in place are slowly breaking up.