Relating colour, chemical and physical characteristics of artificially light-aged New Zealand plant fibres

Light ageing of naturally dyed plant fibres can cause colour change, alteration of molecular bonds within the fibre structure and loss of mechanical integrity. Lighting guidelines seek to protect artefacts by limiting light exposure, for example by estimating the lux hours likely to cause colour change of ‘one just noticeable fade’ (1JNF). However, the extent of associated molecular or mechanical damage is rarely simultaneously assessed. This paper reports a pilot study investigating the effects of accelerated light ageing on muka (fibre extracted from the leaves of Phormium tenax), the most common fibre used in Māori textiles. Non-dyed and dyed muka were artificially light aged and microfaded to ascertain exposure resulting in 1JNF. Ramanmicroscopy and tensile testing of individual fibres from the same samples were used to explore correlations among fading, molecular change and mechanical properties.