New insights into the fading problems of safflower red dyed textiles through a HPLC-PDA and colorimetric study

Safflower is well-known by textile conservators and restorers as the red dye source that produces a nice, though very delicate pink colour that is extremely light-sensitive. The fading due to light sensitivity can be seen in many historical silk fabrics from the most renowned museums and it is a major challenge for textile conservators. However, the fading is not only a result of light exposure, as fabrics stored for many years in dark museum storage also exhibit gradual decolouration. The aim of this study is to increase knowledge on the environmental parameters involved in the degradation processes of carthamin, the main red dye constituent of safflower (Carthamus tinctorius L.). The newly gained information will contribute to a more realistic perspective on the problems of fading of safflower-dyed textiles, possibly helping their conservation. To evaluate the stability of safflower red, specific ageing tests were carried out on new silk samples, dyed with safflower through modern recipes deriving from traditional ones. For the artificial ageing, the effects of simulated sunlight, temperature, humidity and ozone were separately investigated through HPLC-PDA analysis and colorimetric examinations. The results confirmed that safflower red degrades most rapidly under light exposure. They also revealed an important instability of the carthamin dye constituent in a dark environment, especially when subjected to high humidity conditions. Moreover, the HPLC-PDA study was able to provide new insight into the different markers (e.g. Ct components) that are commonly revealed in historic objects dyed with safflower red, but that still have unclarified origins.

Safflower is well-known by textile conservators and restorers as the red dye source that produces a nice, though very delicate pink colour that is extremely light-sensitive. The fading due to light sensitivity can be seen in many historical silk fabrics from the most renowned museums and it is a major challenge for textile conservators. However, the fading is not only a result of light exposure, as fabrics stored for many years in dark museum storage also exhibit gradual decolouration. The aim of this study is to increase knowledge on the environmental parameters involved in the degradation processes of carthamin, the main red dye constituent of safflower (Carthamus tinctorius L.). The newly gained information will contribute to a more realistic perspective on the problems of fading of safflower-dyed textiles, possibly helping their conservation. To evaluate the stability of safflower red, specific ageing tests were carried out on new silk samples, dyed with safflower through modern recipes deriving from traditional ones. For the artificial ageing, the effects of simulated sunlight, temperature, humidity and ozone were separately investigated through HPLC-PDA analysis and colorimetric examinations. The results confirmed that safflower red degrades most rapidly under light exposure. They also revealed an important instability of the carthamin dye constituent in a dark environment, especially when subjected to high humidity conditions. Moreover, the HPLC-PDA study was able to provide new insight into the different markers (e.g. Ct components) that are commonly revealed in historic objects dyed with safflower red, but that still have unclarified origins. (C) 2018 Elsevier Masson SAS. All rights reserved.