Assessment of a NIR spectrometer for surveying plastics - a collaborative investigation into the use of the SurveNIR

Summary

Plastic materials in heritage collections present an increasing preservation challenge as collections grow and include progressively more modern materials. Informed decisions on conservation methods and preventive preservation can only be taken if the objects’ material compositions can be correctly identified and there is a need for simple and reliable methods of identifying plastics. In order to survey a collection efficiently and economically, the analytical method of choice should be reliable, portable, comprehensive and fast. Near infrared (NIR) spectroscopy can meet these requirements and is increasingly used in heritage science. [1]

Between 2005-2008, the EU funded a research project called SurveNIR- Near Infrared Spectroscopy Tool for Collection Surveying, where a NIR spectrometer was modified and the accompanying SurveNIR software developed. The system is designed to investigate a range of chemical and physical properties of paper in a fast and non-invasive manner.[2] The Swedish National Archives participated in the project and acquired the instrument. The instrument's software also contains a less extensive application for plastics and one for negatives and film-materials. These applications have to a large extent been untried for collections and there was a need to validate their use.

In a collaborative project between the Swedish National Archives (“National Archives”), the Swedish National Heritage Board (“National Heritage Board”) and the Swedish Army Museum (“Army Museum”) the feasibility of using the SurveNIR instrument for the identification of plastics in collections was assessed. Questions the project aimed to answer were:

• How reliable is the SurveNIR for plastics identification?
• What are its limitations in regard to the analysis of plastics?
• How user friendly is it and
• What further developments are needed?

Additionally, the project highlighted certain objects or material classes that are in need of particular conservation attention as the testing of the instrument was carried out in combination with condition assessments.

The project was carried out in four stages:

• Introductory workshop and training session on the SurveNIR with the instrument’s developer Dirk Lichtblau e.K.
• Testing the SurveNIR at the National Heritage Board with cross-referencing with known samples and FTIR as a reference technique;
• Testing it on selected objects at the Army Museum and
• Testing it at the National Archives, in Marieberg and Arninge.

[1] Richardson et al. 2007; Richardson et al. 2007 (conference paper); Richardson et al. 2008

[2] Trafela et al. 2008; Rohde, M, Lichtblau, D. 2013