Grading textile fastness. Part 4: An inter‐laboratory trial using DigiEye systems†,‡

In Part 1 of this series of papers, a new method for assessing textile fastness using an imaging system based upon a digital camera was introduced. In Parts 2 and 3, all available experimental data were used to develop new fastness formulae for assessing staining and change in colour, respectively. The combination of the digital method and the two formulae markedly outperformed the current ISO formulae. In the present study a further inter‐laboratory trial has been conducted under the auspices of TCI/81, Colour Fastness and Colour Measurement Committee. Twelve laboratories and 38 professional assessors took part in this trial. Two Digi‐Eye systems were used to measure all the colours. The results provide strong evidence that the newly developed formulae together with the digital imaging method can accurately predict the visual results.     

Grading textile fastness. Part 2; Development of a new staining fastness formula

In the first paper in this series, the results obtained showed that the present ISO standard for assessing staining fastness gave a poor performance with the experimental data accumulated. This paper describes the development of new formulae to fit not only the new data sets described earlier but also another set which was used to derive a previous UK staining formula. The results show that the new formulae developed can fit all these data sets very well. It even out-performed the panel of observers from different laboratories.     

Grading textile fastness. Part 1; Using a digital camera system

This paper describes an imaging system based upon a digital camera for assessing the fastness of textile materials to staining and colour-change. Large sets of samples were assessed by a panel of professional assessors and these results were used to evaluate the inter-observer and between-laboratory variations, and the instrumental method against the visual results. In addition, the measured results from a camera imaging system and a spectrophotometer are compared. The results show excellent agreement between the two instrumental methods. The agreement is even better than the inter-observer and between-laboratory agreements. It was also found that the present ISO standard formula gave a very poor prediction to the visual results for staining fastness. After a simple correction, the formula fits the data much better. In conclusion, applying a digital camera system plus a revised ISO formula can provide an accurate and rapid method for assessing textile fastness.     

A classification system to enhance light‐fastness data interpretation based on microfading tests and rate of colour change

In general light‐fastness tests are carried out by comparing the colour change of a sample to the colour change of Blue Wool Standards in the same illumination conditions. With the microfading technique, developed to test the light fastness of a tiny test area on objects of cultural value, this comparison is made by absolute colour change after exposure. This article presents a new approach to enhance data interpretation of light‐fastness tests by the use of the rate of colour change. The procedure is combined with the conventional classification process using absolute colour change. The new classification system with the rate of colour change was applied to 44 samples, 13 of them were classified in more sensitive Blue Wool categories when analysing the rate of colour change. The perspective of rate of colour change helps to enhance data interpretation especially of samples showing fading characteristics different from the light‐fastness standards.     

Instrumental methods for assessing colour fastness. Part 2 — Staining

In Part 1 of this paper, different fastness formulae for change in colour were compared. In the present report, the same methodology was used to compare different staining formulae. A set of experimental results was used to test the performance of various staining formulae. The constant grade contours for each formula were also calculated. Their patterns were compared and their differences were identified.     

Comparison of instrumental methods for assessing colour fastness. Part 1 — Change in colour

Different instrumental methods for assessing change in colour are described. A set of experimental results were used to test the performance of the various formulae and to illustrate the lack of agreement between them and visual results. Each method is based on a different colour-difference formulae. The differences between the formulae are illustrated by plotting constant AE contours for each of the formulae for various colour centres. The areas of colour where the formulae differ most from each other have been identified. The differences between the methods in some areas were very large, up to a factor of five in terms of ΔE, or two full grades of fastness.     

Colour fastness properties of alkali-clearable azo disperse dyes containing a fluoro-sulphonyl group

The colour fastness properties of alkali-clearable azo disperse dyes containing a fluorosulphonyl group have been investigated. In particular, the colour fastness properties of alkali-cleared poly(ethyleneterephthalate) were compared with those of conventional reduction-cleared poly(ethyleneterephthalate). Specifically, 4-aminoazobenzene dyes containing a nitro group in place of the fluorosulphonyl group in the 4'-position were synthesised in order to compare their fastness properties on poly(ethyleneterephthalate) with those of the 4'-fluorosulphonyl analogues.     

Dyeing and fastness properties of benzodifuranones, naphthodifuranones and naphthofuranonepyrrolidones

Dyeings were carried out on polyester with benzodifuranones, naphthodifuranones and naphthofuranonepyrrolidones (which had been synthesised previously) to study dyeing properties. Symmetrically and asymmetrically substituted naphthodifuranones showed poor dyeing properties in terms of dyeing and fastness. Asymmetrically substituted red benzodifuranones showed excellent dyeing properties and fastness. Asymmetrically substituted blue benzodifuranones showed good dyeing properties; however, the colour hue was dull and the light fastness was inferior. The naphthofuranonepyrrolidones showed similar dyeing and fastness to those of symmetrically substituted naphthodifuranones, but the colour hue was duller.     

Investigation into the effect of a plant‐derived stabiliser on the light and wash fastness of sulphur‐dyed cotton and nylon fabrics

In this study, cotton fabric and nylon fabric were dyed with a range of commercial sulphur dyes and the light and wash fastness of the coloured fabrics was investigated. The effect of after‐treating the coloured cotton and nylon fabrics with a tannin‐based commercial product, Bayprotect Cl, in the presence or absence of sodium sulphate in the treatment bath, was found to significantly improve the light fastness of the sulphur‐dyed cotton, and the photoprotective effect was partially stable to ISO 105‐C06 washing. In addition, the tannin‐based after‐treatment also improved the colour stability of the dyed fabrics to the perborate‐based ISO 105‐C06 washing. The possible mechanisms for the improved fastness properties are also discussed. The application of sulphur dyes to nylon is potentially commercially useful but has been limited because of the reported poor light fastness of the dyeings. The photoprotective effect of the tannin‐based after‐treatment was investigated with a view to providing the necessary commercial performance. However, it was established that on this fibre, the light fastness improvement was marginal, and the associated wash fastness to oxidative bleach‐based ISO 105‐C06 washing was limited.     

Colour fastness to industrial laundering: an international inter‐laboratory trial of the proposed ISO 105‐C12 test procedure†

A new laboratory single‐wash test procedure that describes four test conditions, ISO 105‐C12, has been developed to assess the colour fastness of textiles under industrial laundry conditions. Following an international trial, the intra‐laboratory repeatability and the inter‐laboratory reproducibility of the test were found to be fully acceptable. The results obtained under two of the laboratory test conditions were compared with five washes in an industrial laundry under similar conditions and acceptable correlations were found.     

BFD (l:c) colour-difference formula Part 2-Performance of the formula

The available experimental data relating to small colour differences between pairs of surface colours have been combined together into two sets including perceptibility results (CP) and acceptability results (CA). A new colour-difference formula, BFD(\:c) has been developed using the combined experimental results. For small colour differences, particularly when perceptibility judgements are involved, the new formula represents a substantial improvement over other fomulae. For large colour-differences the new formula is close to the best available formula. Different 1 values are required for perceptibility and acceptability judgements, and for large colour differences, but c=1 in all cases. The BFD formula gives the best possible results obtainable with currently available data. Analysis shows that results from different studies, including those based on perceptibility and acceptability judgements, are compatible in many respects. Discrepancies that were detected seemed to be due to experimental error, or problems in scaling the visual results. However, there are major differences between the results for small differences between surface colours and those implicit in the Munsell system and MacAdam ellipses.     

Structure—wet fastness relationships of some blue disperse dyes for polyester

A range of monoazo blue disperse dyes has been synthesised by coupling benzenoid and heterocyclic diazo components to aniline derivatives containing ester functions. The colour properties and wet fastness of the dyes on polyester at 1/1 standard depth have been examined and rationalised in terms of dye structure. Styryl dyes have also been prepared in order to compare their wet fastness properties to those of the azo dyes.     

An investigation of an instrument‐based method for assessing colour fastness to light of photochromic textiles

A new method for evaluating the light fastness of photochromic fabrics was established, aimed at replacing the conventional method with an instrumental method. This method was based on comparing the colour difference of photochromic fabrics after light exposure with measured values of the colour differences of the blue wool references after fixed periods of light exposure. This method benefits from replacing the traditional visual evaluation of colour difference between exposed and unexposed areas of textile samples with a more accurate, instrument‐based measurement of the colour difference. The light fastness is then evaluated by comparing the colour difference with tabulated values of colour differences brought about by light exposure, for increased periods of time, of standard blue wool references. This method could be used for measuring light fastness of both traditional and photochromic fabrics. However, blue wool references and tested samples should be exposed to light under similar conditions when using this method to measure colour fastness to light of fabrics.     

An Evaluation of the AATCC Light–fastness Reference Fabric

The purple reference fabric (LRF-1) proposed by the AA TCC for the calibration of fading lamps together with the ISO Blue Wool Light–fastness Standards 1–5 and the AA TCC Blue Wool Light–fastness Standards L2–L5 were exposed in the Xenotest 150 under different effective humidity conditions, as well as in daylight. It is concluded that, for use in calibrating fading lamps, the LRF–1 fabric shows no advantages over the Blue Wool Standards. On the contrary, its very high heat–sensitivity is a serious defect. As a light–fastness standard it is use/ess, in view of its low fastness to light.     

Colorimetric Evaluation of Change in Colour

This paper is sponsored by the Fastness Tests Committee to give the maximum time for testing and evaluating the proposed formula before the next ECE and ISO meetings. Members of the Fastness Tests Committee have not yet had time to study in full the results presented in the paper, and therefore do not necessarily agree with the views expressed by the author. (The paper was previously published in German in the September 1986 issue of Textilveredlung.) In the paper a formula is presented for the evaluation of the change in colour that provides for the determination of fastness ratings by means of colour-difference measurements. The results agree well with the mean judgement of experienced assessors, who determined the ratings by means of the ISO 105-AO2 grey scale.     

Dyeing and fastness properties of phthalimide‐based alkali‐clearable azo disperse dyes on poly(ethylene terephthalate)

The properties of a series of phthalimide‐containing azo disperse dyes and azo dyes with N‐methyl phthalimide moieties in their diazo component were investigated and compared when used to colour polyethylene terephthalate. The N‐substitution of the phthalimide gave a hypsochromic effect on the colour change and better colour yields on poly(ethylene terephthalate) fabrics, probably because of the electron‐donating property of the methyl group and the higher hydrophobicity of phthalimide‐containing azo dyes compared with those containing phthalimide moieties. The results show that phthalimide‐based azo disperse dyes have excellent dyeing fastness properties and that high wash fastness can be achieved using alkali clearance. This alternative clearance method is important for reducing the environmental impact of the dyeing process by replacing reductive clearing and, in particular, by removing the need for sodium hydrosulphite, which creates a high biological oxygen demand when released in conventional disperse dyeing effluent and which generates aromatic amines.     

High fastness heterocyclic azo disperse dyes bearing ester functions

Blue monoazo disperse dyes bearing carboxylic acid ester functions have been synthesised from thiophene diazo components in the search for colorants of high fastness and reduced environmental impact. The colour properties of the dyes in solution and on polyester, as well as the fastness of the dyes when applied to polyester, are examined and rationalised in terms of dye structure.     

Effect of sleeve colour and background colour on change in colour assessments†

The two standard grey scales, ISO 105‐A02 and ISO 105‐A03, used for assessing change in colour and staining, respectively, are both typically provided mounted in black material and within a black sleeve. However, some grey scales are now provided mounted in grey material and within a grey sleeve. This paper reports psychophysical data and shows that the change in colour grades obtained from grey scales are not affected by the background colour of the viewing cabinet. A small, but statistically significant, effect is found for the colour of the sleeve with higher grades being found when using the black sleeve compared to when using the grey sleeve. However, when the samples being assessed are masked by a sleeve of the same colour as that used with the grey scale, an extensive field trial shows that the colour of the sleeve does not affect the change in colour grades obtained under commercial conditions.     

Dyeing treatments for protecting colour and colour fastness of green bamboo culms

The effects of various dyestuffs and treatment conditions on the epidermis colour of ma bamboo (Dendrocalamus latiflorus), moso bamboo (Phyllostachys pubescens), and makino bamboo (P. makinoi) were examined to determine the most appropriate dyeing material and approach for endowing bamboo culms with a fascinating green colour without removal of their epidermis. Experimental results revealed that excellent green colour was obtained when the three species of bamboo culms were treated with 0.25% basic dyes in an 80 °C water bath for 30 min (a* values of −19.6, −15.4, and −16.0, respectively). Moreover, alkali pretreatment, though contributing to dyeing effectiveness, yielded bamboo culms with dim surface lightness of low L* values. Dye makino bamboo culms without colour fixation post-treatment changed from green to light green after indoor exposure for 1 year, exhibiting unstable indoor colour fastness. In contrast, colour fixation post-treatment was found to improve colour fastness of bamboo culms; in particular, treatment with 1% glacial acetic acid or 3% tannic acid achieved more uniform dyeing effectiveness and better indoor fastness. By inhibiting discoloration, the natural beauty of bamboo culm can be preserved and its service life can be extended.     

Improvement of light fastness of natural dye: effect of ultraviolet absorbers containing benzotriazolyl moiety on the photofading of red carthamin

While the contribution of ultraviolet absorbers to synthetic dyes has been investigated by several workers, there have been few studies pertaining to the use of functional ultraviolet absorbers as a means of improving the light fastness of natural dyes. In this paper, numerous potential ultraviolet absorbers were prepared to prolong the life of natural dye carthamin. The effects of these compounds in reducing photofading were examined on a polymer substrate. The use of commercial ultraviolet absorbers was not necessarily useful in improving the light fastness of the colour. However, benzophenone‐type ultraviolet absorbers containing a built‐in ultraviolet absorber moiety markedly retarded the photofading rate. It is proposed that 2,2′,4,4′‐tetrahydroxy‐5‐methylbenzotriazolylbenzophenone and its derivatives may be used as effective stabilisers in the fading of natural dyes.