A comparison of NIR spectroscopy and colour measurements for the classification of radiata pine timber thermally modified over a narrow temperature range

Armin Thumm; Rosie Sargent; Steven Dovey; Tripti Singh; Catherine Nicholson; Christina Howat; Joel Kidgell; Simon Hinkley

doi:10.1007/s00107-025-02268-2

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A comparison of NIR spectroscopy and colour measurements for the classification of radiata pine timber thermally modified over a narrow temperature range

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A comparison of NIR spectroscopy and colour measurements for the classification of radiata pine timber thermally modified over a narrow temperature range

Armin Thumm, Rosie Sargent, Steven Dovey, Tripti Singh, Catherine Nicholson, Christina Howat, Joel Kidgell and Simon Hinkley

European Journal of Wood and Wood Products, Vol.83(3), pp.1-10

2025

DOI: https://doi.org/10.1007/s00107-025-02268-2

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Abstract

The New Zealand Building Code is unique in the world in having prescribed durability requirements for all building elements, including interior timber such as flooring. Heavy metal preservatives are still used extensively for this purpose, despite being banned in many other countries. Thermal modification of wood increases timber durability without relying on chemical additives. This involves heating the wood in a carefully controlled environment with the modification settings being specific to the process and the species. Thermal modification induces chemical changes in the wood structure that can be identified using spectroscopy. Correlation of chemical changes to specific processing conditions for a particular wood species may then enable independent verification of the modification temperature. This is a crucial aspect of product compliance with the New Zealand Building Code. Without being able to verify the modification temperature, evidence of compliance with these stringent durability requirements is extremely difficult. In this study, near-infrared (NIR) spectroscopy was investigated as a tool for developing a quality assurance/quality control (QA/QC) methodology, to ascertain the claimed heat treatment levels have been applied to thermally modified timber products. NIR spectroscopy is also compared to techniques based on colour changes of heat-treated timber. It was found that a predictive classification model, based on NIR spectra from solid wood surfaces, was able to predict 100% correctly the 3 treatment levels of thermally modified timber used in this study (210 °C, 220 °C, 230 °C). It was superior to a L*, a*, and b* colour model (87% correct) and a visible colourimetry spectrum model (95% correct).

Details

Title: A comparison of NIR spectroscopy and colour measurements for the classification of radiata pine timber thermally modified over a narrow temperature range
Authors: Armin Thumm (Corresponding Author) - Scion
Rosie Sargent - Scion
Steven Dovey - Scion
Tripti Singh - University of the Sunshine Coast, Queensland, National Centre for Timber Durability and Design Life
Catherine Nicholson - Building Research Association of New Zealand
Christina Howat - University of Canterbury
Joel Kidgell - Victoria University of Wellington
Simon Hinkley - Victoria University of Wellington
Publication details: European Journal of Wood and Wood Products, Vol.83(3), pp.1-10
Publisher: Springer
Date published: 2025
DOI: 10.1007/s00107-025-02268-2
ISSN: 1436-736X; 0018-3768
Copyright note: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Data Availability: No datasets were generated or analysed during the current study.
Grant note: This work was funded by the New Zealand Ministry for Business, Innovation and Employment Strategic Science Investment Fund, under Scion’s Manufactured Products from Trees Science Platform (C04 × 1703). This research was also supported by the Building Research Levy and a Victoria University Summer Research Scholarship.
Organisation Unit: National Centre for Timber Durability and Design Life
Language: English
Record Identifier: 991130081102621
Output Type: Journal article

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Collaboration types: Domestic collaboration; International collaboration
Web Of Science research areas: Forestry; Materials Science, Paper & Wood