Fergusson washed navy and black reactive-dyed cotton single jersey in water only, then exposed it to light while wet. By the end of the exposure series, every dyeing except Levafix Navy Blue E-BNA faded more wet than dry, “indicating that the moisture content of the fabric is contributing to the rate of fading on exposure to light.”
Which blue reactive dye types did Kabir, Raafi and Koh find most and least stable to light on cotton single jersey?
“Anthraquinone based reactive dyes shows the highest photo stability on sunlight and xenon arc lamp exposure among all the selected blue dyes. In addition, di-fluro pyrimidine vinyl sulphone based azo dyes were shown most sensitivity to exposure of sunlight and xenon arc lamp exposure.” Kabir, Raafi and Koh reached this after dyeing cotton single jersey with five blue reactive dyes at 1%.
The authors tied the anthraquinone dye’s stability to its fused benzene ring structure. For the DFP-VS dye, they pointed to the two fluorine atoms and one chlorine atom on its pyrimidine ring.
Kabir’s DFP-VS dye carries the same C.I. number as Levafix Navy Blue E-BNA, one of the navies Fergusson tested.
| Dye | C.I. number | Chromophore | ΔE, sunlight | ΔE, xenon arc lamp |
|---|---|---|---|---|
| Dye 1 | C.I. Reactive Blue 19 | Anthraquinone | 0.5 | 1.5 |
| Dye 3 | C.I. Reactive Blue 198 | Di-azo bifunctional (MCT-VS) | 0.8 | 2.2 |
| Dye 2 | C.I. Reactive Blue 21 | Copper phthalocyanine | 1.2 | 3 |
| Dye 5 | C.I. Reactive Blue 225 | Di-azo bifunctional (DFP-VS) | — (not stated in the text) | 5.5 |
Did Kabir, Raafi and Koh’s xenon arc lamp fade blue reactive dyes on cotton single jersey the way outdoor sunlight did?
“A comparison for the fading rates of sunlight and xenon arc lamp showed similar trends,” Kabir, Raafi and Koh wrote of their blue reactive dyeings on cotton single jersey. Fading grew with exposure time under both sources. They also reported that “the level off point for faded cotton fabrics were obtained at 72 hr of exposure for sunlight and xenon arc lamp.”
For every dye with both values in Table A, the xenon value is higher than the sunlight value.
The two exposures ran under different conditions. The sunlight samples sat on an outdoor rack over successive seasons and were kept in the dark between periods. The xenon samples ran in a light fastness tester with controlled humidity and black panel temperature.
Did Fergusson find that two navy reactive dyes with the same Colour Index number fade alike on cotton single jersey?
“Such a result would indicate that even though the two dyes are listed under the same C.I. number, there are substantial chemical differences between them,” Fergusson wrote of two navies on cotton single jersey. They were Sumifix Supra Navy 3GF and Intracron Dark Blue CDX, both listed as C.I. Reactive Blue 222.
Under dry exposure, the two dyes faded at a similar rate at first. Sumifix Supra Navy 3GF then faded further as exposure went on. Fergusson’s thin-layer chromatography showed that “none of the dyes in the study were pure chemical entities”. He put the gap possibly down to shading colours, different isomers formed in reaction, or both.
Wet exposure after washing separated the pair as well. Fergusson noted they were dyed at the same tinctorial strength, so a strict comparison was fair, and still found significant differences in how they faded.
What did Fergusson find when navy and black reactive-dyed cotton single jersey was washed with a perborate detergent and then exposed to light wet?
“The presence of an oxidizing bleach (sodium perborate) in the detergent increased colour loss during washing and wet exposure to light,” Fergusson wrote of his navy and black reactive dyes on cotton single jersey. Each wash was followed by a two-hour exposure to light, starting wet. The front-load detergent carried the perborate.
In Table B, the front-load detergent gave the highest colour difference for every dyeing except Sumifix Supra Navy 3GF, where the top-load and front-load detergents tied.
Fergusson did not pin the front-load result on the bleach alone. His front-load wash also used less water per kilogram of fabric, harsher mechanical action from that smaller volume of water, and a stronger detergent solution. “It is most likely that all these factors contributed to the colour changes found.”
His neutral detergent contained no alkali or buffer salts. Yet it gave a larger colour difference than the top-load detergent for Cibacron Super Black R, Cibacron Navy LS-G and the lighter Remazol Navy RGB dyeing.
| Dye | Neutral detergent | Top-load detergent | Front-load detergent (with sodium perborate) |
|---|---|---|---|
| Cibacron Super Black R | 5.8 | 4.3 | 8.3 |
| Cibacron Navy LS-G | 4.8 | 3.9 | 6.6 |
| Levafix Navy Blue E-BNA | 3.5 | 4.1 | 6.1 |
| Sumifix Supra Navy 3GF 150% | 4.7 | 5.2 | 5.2 |
| Remazol Navy RGB 150%, 3.0% depth | 3.9 | 4.2 | 6.5 |
| Remazol Navy RGB 150%, 1.5% depth | 5.4 | 5.1 | 10.1 |
Sources: Kabir, S.M.M., Raafi, S.M. and Koh, J. (2020). “Photofading Mechanism of Reactive Blue Dyes on Cotton against Sunlight and Xenon-arc lamp”. Journal of Textile and Apparel, Technology and Management 11(4), NC State University. https://jtatm.textiles.ncsu.edu/index.php/JTATM/article/view/18223. Fergusson, S.M. (2008). “The Effect of Laundry Detergents and Residual Alkali on the Light Fastness of Reactive Dyes on 100% Cotton”. MTech thesis, RMIT University. https://research-repository.rmit.edu.au/articles/thesis/Effect_of_laundry_detergents_and_residual_alkali_on_the_light_fastness_of_reactive_dyes_on_100_cotton/27576339.
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