Why identify the material?
It is good practice to identify the material of which an object is made because it enables you to understand more about the object. But it is vital for objects made of plastics as it will help you know how best to look after them.
All plastics degrade over time but some are much less stable than others. It makes sense to concentrate limited resources on providing objects made of these plastics with optimum environments or you might even decide not to collect such objects at all. To find out which materials these are go to Problem plastics.
The best way to learn to identify different plastics is to study a group of objects that already have the plastic from which they are made identified. That way you can get to know what they look, feel and smell like. Clues to help you know what to look for can be found at Identification: clues to get you started.
Identification can also involve sophisticated analytical equipment of which the Fourier Transform Infrared Spectrometer (FTIR) is the most widely used. Such machines can be brought to your museum at a cost. It does however require experts to carry out the analysis and opinions differ on its value.
For information on this and other forms of instrumental analysis please refer to Anita Quye and Colin Williamson ed., Plastics collecting and conserving, part two: analytical methods, pp.70 -73.
Clues to get you started
There will always be something you can glean from an object itself to help you decide what material it is made of or how it was manufactured. If you have any thoughts to contribute to the questions below click on them and find out how what you know may help. The notes attached to each question aim to help you make the most of what you know about the object to narrow down the options. Once you have done that you can go to the particular materials in the Plastics materials or the particular manufacturing processes in the Manufacturing processes to look in more detail at what you have decided are the probabilities.