On-Site Non-Destructive MID-IR Spectroscopy of Plastics in Museum Objects Using a Portable FTIR Spectrometer with Fiber
- PDF / 1,011,576 Bytes
- 6 Pages / 398.7 x 621 pts Page_size
- 77 Downloads / 185 Views
response to environmental conditions and therefore have different storage and display requirements. The correct identification can aid in determining provenance. For example, is the object made of tortoiseshell or cellulose nitrate? Distinction of imitations and fakes from authentic objects can be of great art historical significance or have great financial implications. A lump of ancient amber with a lizard in it will likely be a more valuable natural history specimen than will a lump of modem polyester casting resin with a lizard. Thus identification of plastics is important. Identifications have been attempted by such non-chemical means as connoisseurship, style of object, trade names, patent numbers, name of manufacturer; and by chemical means such as density using float tests, solubility, bum and sniff tests, response to test reagents in spot tests, infrared spectroscopy, and gas, liquid, and thin layer chromatography. Spots tests are the easiest methods to use in the field. Unfortunately non-chemical and non-instrumental identification methods, including spot tests, are subject to many limitations and often result in ambiguous, or worse, incorrect identifications. Infrared spectroscopy is recognized as the most precise and widely applicable technique for plastic identification. This technique has the disadvantage of requiring special equipment that is usually located at some laboratory that is remote from the object, so it is necessary to take the object or a piece of the object to the spectrometer. Transporting objects can be harmful and certainly is expensive. Taking samples is time consuming, and is 25 Mat. Res. Soc. Symp. Proc. Vol. 462 ©1997Materials Research Society
frowned on by conservators and curators when requested for a purpose that is not considered to be absolutely necessary, such as a general survey of a collection to determine the composition of the objects in the collection, no matter how small the sample may be. This paper describes the use of a portable IR spectrometer with a fiber optic sampling probe that overcomes difficulties related to sampling and spectrometer location, and that is suitable for analysis and identification of plastics and polymeric materials in museums. It is particularly suited to analytical surveys of entire collections to identify all the plastics present. The analyses are performed, not at the CCI laborartories, but on-site, in-situ, in museums and art galleries across the country, in such potentially cramped locations as storage rooms, exhibition areas, display cases, and the like. The objects may be in the conservation studio, hanging on the wall of an exhibition, or in drawers in storage areas. Not only is taking samples not necessary, objects do not even need to be moved from their current locations in the museum. EXPERIMENT The instrument consists of separate modules, as shown in Figure 1. The IR source is a MIDAC Illuminator FTIR Spectrometer with a silicon carbide glower source operated at 1650 K and a Michelson interferometer (Figure 1, bottom module on c
Data Loading...
