Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Compilation of dye degradation profiles for the light ageing of historical dyestuffs

Optimum conditions for the light-ageing of dyestuffs using a light-box from Complete Lighting Systems were determined (WP1), with ageing study samples taken at intervals up to 4,500h at 8kLux (ambient temperature/humidity):"Model" samples of wool and silk yarns, dyed according to historical recipes were aged under this regime (WP2) and dye degradation profiles have been established which confirm the relative rates of ageing of a number of historically important dyestuffs (WP5).

These dye degradation profiles have allowed us to establish the following important variations in component ranges for historical dyestuffs, which have in turn allowed the identification of these dyestuffs by our colleagues at the National Museums of Scotland and KIK to be made with greater confidence (WP5):
- the ageing of the quercetin/kaempferol (flavonol) component is around 6 times faster than that of the luteolin (flavone) component of sawwort;
- there is no variation in the rate of ageing of flavone dyestuffs (luteolin) in samples which were dyed firstly with weld, followed by indigo, or alternatively with indigo followed by weld;
- in silk dyed with dyers greenweed, the initial ratio of genestein and luteolin varies according to the dyeing procedure so this parameter should be used with caution in the analysis of aged historical samples;
- degradation of the red dyestuff madder is much slower than that of the flavonoid yellows and the two main components of madder degrade at significantly different rates; carminic acid (from the red dyestuff cochineal) also degrades at a much slower rate than the flavonoids.

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