–> Preventive conservation

Trick : Detecting chlorine in plastic

Jacques Rebière (Laboratory of Conservation, Restoration and Research in Draguignan) presents a way of detecting chlorine in plastic.
In the heritage domain there is a problem concerning the proper storage of objects and how to store them for a long time. The time frame is often a year, sometimes a decade, and it happens that some storage materials are harmful for the conservation of objects, in the medium or long term. One of the contributing factors to deterioration are chloride ions, which enter the composition of certain polymers (certain plastics). There is a very simple method to find out if a plastic, which is a made of an unknown material, contains chlorides or not. This test requires only a few things: all you need is a blowtorch, wooden tongs so that you do not burn your fingers and, most importantly, a copper wire. The procedure is very simple: you light the blowtorch and then bring the copper wire to the flame. When the wire is red, you can touch it to the sample from the material to test it. The material is burned for testing and then the wire is held to the flame again. If there is no reaction that means there are no chlorides in the material. In contrast, if I take this film made of PVC, you can clearly see a very bright green flame appear; this indicates the presence of chlorine in the plastic material.

Trick : Detecting a polythene or polypropylene plastic

Jacques Rebière (Laboratory of Conservation, Restoration and Research in Draguignan) presents a way of detecting a polythene or polypropylene plastic.
It is understood that certain plastics – certain polymers – should be banned when storing objects; there are others that should be chosen. In particular we know that polyethylene or polypropylene are two polymers – two plastic materials – which are likely to deteriorate in this time frame. However the degradation does not produce pollution that is capable of damaging the objects that are in close proximity. How can you tell if you are dealing with a polyethylene, a polypropylene or something else? There is a simple way to find out, and the method can be applied to dense plastics. A foam-based plastic containing air is not applicable to this test. I have here two samples and a beaker full of water. I am going to put the samples in the water and you can see immediately that one plastic continues to float, and the other sinks. This is simply because the polyethylenes or polypropylenes have a density lower than 1. They are the only plastics of this type that float in water and by this simple method we know that the orange sample should theoretically be avoided when storing heritage objects long term.

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