New Study Maps Light-Induced Damage in Harakeke Fibers

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A recent study shows how infrared (IR) and Raman spectroscopy are being used to help preserve culturally significant Māori textiles. This study, published in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, demonstrates how advanced spectroscopic techniques can detect long-term degradation in harakeke (New Zealand flax, Phormium tenax) fibers traditionally dyed with iron-tannate mixtures (1).

The Māori people are the indigenous people of New Zealand (1–3). Because of colonization by European settlers in the 1800s, some of the Māori’s culture, including its language, tools, and way of life, began to gradually decline (2,3). Today, the Māori are primarily concerned with preserving their history and cultural heritage, which includes preserving their historical artifacts.

One of these historical artifacts are harakeke fibers. These are dyed black and woven into a wide range of garments and cultural objects and hold deep cultural significance across indigenous Māori communities (1). However, experts have long struggled to quantify and predict the chemical pathways behind their deterioration when exposed to prolonged lighting conditions in museums and collections.

In their study, the research team, comprised of researchers from the University of Otago and Flinders University, investigated how lighting conditions in museums can impact harakeke fibers. To do so, they simulated decades of natural aging through artificial light exposure in order to understand and track chemical changes that compromise durability and appearance (1).

Both IR and Raman spectroscopy was used for this analysis, and both techniques uncovered several important details. For example, the researchers found that IR spectroscopy was able to differentiate fibers by their dye status and even identify the specific tannin sources used, which was either the condensed tannin from hinau (Elaeocarpus dentatus) or the hydrolysable tannin from manuka (Leptospermum scoparium) (1). Meanwhile, Raman spectroscopy achieved similar discrimination, separating dyed from undyed fibers while also pinpointing tannin varieties with high precision (1).

Another important aspect to this study was how Raman and IR spectroscopy revealed light-aging signatures. Non-dyed fibers exhibited a measurable increase in cellulose crystallinity over time, which is a change researchers associated with structural brittleness (1). Meanwhile, hinau-dyed fibers showed rising oxygen content and acidity, which indicated an accelerated chemical breakdown (1). These results provide crucial evidence that the dyes used in traditional black coloration are not just surface treatments but active chemical agents that determine how the fibers degrade.

As a result, this research collaboration between University of Otago and Flinders University shows how spectroscopy can be utilized to safeguard delicate historical artifacts.

References

1. Samanali, G. A. P.; Lowe, B. J.; Smith, C. A.; et al. Artificially Light-aged, Black-dyed Harakeke Fibres: Understanding the Correlations Between Chemical Composition and Fibre Properties Using Vibrational Spectroscopy and Chemometrics. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2026, 347, 126960. DOI: 10.1016/j.saa.2025.126960
2. Lake Forest College, Maori Language (Te Reo Māori). Lake Forest College. Available at: https://www.lakeforest.edu/academics/majors-and-minors/environmental-studies/maori-language-(te-reo-maori) (accessed 2025-12-02).
3. New Zealand Education, Māori Culture. Government of New Zealand. Available at: https://www.naumainz.studywithnewzealand.govt.nz/discover-new-zealand/life-and-culture-in-nz/maori-culture (accessed 2025-12-02).