SPME fibre inserted into the GCMS
Testing a new identification technique
The problem is, identifying plastic materials visually is really tricky and often unreliable. Fortunately, a range of scientific identification techniques are available to identify plastics much more accurately. However, often these types of analysis require a high level of specialist knowledge to interpret the results, and it is unusual for a museum conservation lab to have ready access to high tech equipment. Most problematically, sometimes these techniques require a sample to be taken from the plastic object- sampling museum objects is of course something we avoid doing as far as possible.
To solve these problems scientists are currently working on new techniques that can be used to accurately identify plastic materials but are also suitable for use on museum objects. The Museum of London recently teamed up with a scientist from UCL’s Institute for Sustainable Heritage to test an emerging plastic identification technique called Solid Phase Microextraction Gas Chromatography Mass Spectrometry (SPME-GC/MS).
There are lots of great things about this technique, but the best features (particularly for museum objects) are that it is entirely contactless and it gives you a really accurate, very detailed plastic identification.
The technique uses coated fibres known as SPME fibres that are specially adapted to pick up the emissions or smells of objects. A SPME fibre can simply be placed in the vicinity of a plastic object and left for around a week to pick up the smells coming from the plastic.