Colour-fastness Assessment of Textile Materials

Colour-fastness Assessment of Textile Materials J. PARK Loughborough Dyeworks Ltd Nottingham Road Loughborough Introduction The fastness testing of coloured textiles is an area of technology which has gained in importance with the passage of time, reflecting the needs of both dye suppliers and users for reproducible test methods for assessing products and the increasing influence of consumer requirements. In the first U.K. publication of methods for fastness testing in 1934 [ l ] , details were given of only light, perspiration and washing tests. By 1948 [2], 33 tests were described, increasing to 42 by 1955 [3], by which time tests were no longer subdivided according to fibre type - all ratings, except those for light fastness, were specified in terms of the Grey Scales. Details of 25 methods proposed as IS0 tests were given [4], and these were subsequently accepted with minor modifications. In the third edition of the Society of Dyers and Colourists’ ‘Standard Methods’ [5] and its Supplement [6] over 50 test methods were included. Papers have dealt with the development of fastness testing in France [7], Switzerland [8], ;he USA [9] and Europe generally [ lo] . The Current review is intended to cover advances during the period from 1967 to 1974, but the opportunity has been taken to summarize work over a longer period. No development has taken place in a large number of test methods. Light Fastness Light-fastness tests are well defined in a British Standard, the latest edition of which appeared in 1971 [ l l ] , when a test based on the xenon arc was included for the first time. It was agreed [gal at the IS0 Meeting in Pans to produce a new test to combine the IS0 and AATCC daylight tests. The factors which are important in relation to the fading of coloured materials have been reviewed [ 121. One author has concluded [13] that sunlight is too variable to give satisfactory test results. Governing factors are the temperature and moisture content of the sample, together with the intensity and spectral distribution of the radiation falling upon it. There seems to be no threshold of radiation intensity below which fading cannot occur. Sylvester [9] stated that fading generally proceeds similarly in both direct sunlight and under glass, although some dyes provide exceptions, mainly those with a light fastness below 4. Fading is most rapid without glass; increasing the thickness of glass decreases the fading rate, 3s does increasing the distance between the samples and the glass. Roessler [14] investigated the effect of daylight on dyed materials at different latitudes in N. America and compared the degree of fading with that of the blue wool standards. The prolonged summer daylight in the far north appears to be important. Azo and anthraquinone disperse dyes generally faded more rapidly in localities of high r.h., and with the anthraquinone dyes examined the light fastness increased as the regain of the substrate increased. The importance of the spectral distribution of the light source used for fading has long been recognized. Cooper and Hawkins [15] investigated a number of light sources and concluded that none had a spectral distribution similar to daylight, although the enclosed carbon arc was similar t o sunlight in the region 300-430 nm. They also observed that the spectral distribution is influenced by the surrounding atmosphere. McLaren [ 161 concluded that the actinic radia- tion emitted by the glass-enclosed carbon arc extends over the same region as daylight transmitted by window glass, namely 330-800 nm. The balance of the radiation, however, is quite different since radiation from the arc is richer in violet and ultraviolet and deficient in the rest of the visible region. The critical wavelength for fading decreases as the light fastness increases, i.e. radiation in the red region is critical for low light fastness and that in the blue region for high fastness. The intensity of the ultraviolet radiation present in sunlight and in skylight, and its strength (in rontgen) was measured using a uranyl oxalate actinometer [17]. The figures obtained agree with those obtained by photocell measurement of light passed through an Ulbricht globe photometer, whereas measurement of direct sunlight by means of a photocell gave variable results. The intensity of the U.V. radiation in the short- and long- wavelength regions depends on the weather conditions. Disperse dyes on synthetic-fibre fabrics and in solution were photodegraded by mono- and poly-chromatic light [ 181 . These dyes were not degraded by light of wavelength above 400 nm. Degradation increased with decreasing wavelength in the absence of extensive light absorption by the polymer and delustrants. It was concluded that any light of 280-700nm enables dyes to be divided into three or four stability groups but the xenon arc probably provides the closest correlation with sunlight fading of dyes. In a critical appraisal of the daylight test, McLaren [19] found that effective humidity (e.h.) is the only factor which causes variability, which is governed mainly by the proportion of sunlight falling on the samples during exposure. It is suggested that the reproducibility of the test is high for the majority of dyed fibres which, :ike the dyed blue wool standards, have low sensitivity to moisture. The test is a reliable guide to the fading which will occur in use, provided that exposures are carried out in the country of use or in a similar climate, with the reservation that the samples should not get wet during exposure . Giles [20] concluded that the light fastness of a dye is higher on a fibre of higher regain (above 4%) but that the reverse is true for fibres with a regain below 4%. Fastness can ,be reduced by foreign materials and finishes on the fibre. The increase in light fastness due to the increase in depth is usually greater with fibres of higher regain and is more pronounced with dyes which are insolubilized within the fibre. Cunliffe [21] reported the influence of temperature and humidity on wool dyes. It was suggested by McLaren [22] that the only suitable method of measuring and controlling humidity, especially in REV. PROG. COLORATION VOL. 6 1975 71 fading lamps, is by the use of a moisture-sensitive pattern whose light fastness-moisture content relationship is known. A red azoic combination dyed on mercerized cotton is suitable. A test to determine the light fastness of patterns at high humidity was proposed [23] in which the daylight- exposure racks face 180' i.e. in the opposite direction to that in the normal daylight test, when an e.h. of about 60% is obtained. Schultze [24] determined the light fastness of dyeings, including blue wool standards 2-5, at various r.h. values and temperatures. The rate of fading increased with the r.h., especially for an azoic dyeing on cotton and several azo-pigment lacquers. Surprisingly, a dyeing of Astrazon Blue G (C.I. Basic Blue 1) on Dralon faded twice as rapidly at 45% as at 85% r.h. The rate of fading steadily increased with temperature in the range 10-40°C, although some samples were more sensitive than others. Methods have been published [25] for determining the fastness of patterns to alternate exposure to water (or sea-water) and light. In AATCC 125-1974, a coloured specimen is immersed in water (distilled, deionized or contain- ing 30 g/l sodium chloride and 5g/l magnesium chloride) and then exposed in a carbon arc for one hour. After storage in the dark for at least two hours, the sample is examined for colour change. The cycle is repeated until a 'just noticeable fade' is observed. AATCC 126-1972 is similar but is designed to simulate the effect of alternate exposure to water (high humidity) and light on coloured materials to predict their behaviour in use. The method is to store the material for 30 min in the dark at high humidity followed by exposure for one hour at low r.h. In both tests, results are expressed as the number of cycles required to produce a contrast equal to grade four on the Grey Scale for Assessing Change in Colour. Bayley and Tweedie reported [26] that with certain dyes, e.g. metal-complex dyes, exposure to perspiration can reduce light fastness. Calin [27] selected dye combinations of suitable light fastness for producing pastel colours 'on cellulose. The fading rates were estimated using the Kubelka-Munk relation- ship to relate reflectance values of patterns exposed in daylight or to a xenon arc to the apparent residual concentration of the dyes; the dyes appeared to fade more rapidly in combinations than in self colours. Moir [28] exposed a range of Courtelle fabrics dyed with single basic dyes, the daylight exposure being measured in langleys. The colour differences between faded and unfaded samples were obtained from reflectance data and then related to blue-scale assesments, using a set of blue standards exposed with the dyeings. The predicted and visual assessments agreed within a half-grade on the blue wool scale. McLaren [29] exposed a series of samples which were then assessed by a number of observers, and found that two-thirds of all assessments were with a half-grade and 95% within one grade of the true result. This did not depend on the experience of the observer. Agreement was greatest for patterns of high light fastness and least with those that faded off-tone. It has also been stated [30] that the results obtained depend on the observer and also that the same observer may assess differently at different times. Fading Lamps Daylight tests are time-consuming; fading lamps have been available for fifty years, the earliest being based on the carbon arc [5]. Burgess [31] pointed out that the carbon arc could give high ratings for many dyeings which had low daylight fastness. Lead [32] compared natural and artificial light sources in relation to the factors that influenced fading and emphasized the importance of humidity control. It was shown [33] that vat dyes on wool and dyeings on synthetic-polymer fibres gave anomalies between daylight carbon-arc assessments. Spectrophotometric measurements made during the fading of dyes on wool and cotton in both daylight and under the carbon arc [34] showed that the fading curves produced by the two sources were similar. Boulton and Guthrie [35] outlined the main features of fading-lamp design, suggesting that temperature and humidity controls should be fitted. It was considered [36] that, although discrepancies between daylight and fading-lamp results may be due to differences in spectral distribution and temperature, the moisture content seemed to be the principal cause. The e.h. during daylight exposure in the U.K. was thought to be 20% [37], but later work indicated [38] that lamps should be operated at an e.h. of 45%. It was shown [39] that the e.h. in fading lamps ranged from 2 to 70%. Lamps running at lower values will give high results with humidity- sensitive dyes, whereas lamps running at high values will give low results - differences may be as great as 2 grades in each case. The excess ultraviolet content of the carbon arc can also cause anomalies even if the correct e.h. is employed. Hoffman [40] described a fading lamp in which the samples were rotated around a light source which combined mercury-vapour and tungsten-filament lamps. A suitable filter was used while cooled and moistened air was circulated in the apparatus. The spectral distribution was similar to that of daylight and the results obtained correlated closely with those obtained in daylight and under the carbon arc. The xenon-arc fading lamp XBF 6000 has been described [41]. This lamp is water cooled and use of a suitable filter gives a U.V. and visible radiation content similar to those of daylight. McLaren indicated [42] that the xenon arc could be easily filtered to give a spectral distribution similar to that of daylight but modification was necessary to obtain the desired e h . A further development [43] of the xenon lamp enabled the front and the back of samples to be exposed in turn by rotating the sample holder, moist air being circulated round the samples and a water jacket fitted between the source and samples to protect them from heat. Patents describe a technique for exposing specimens to varying spectral regions along their length [44] and for separating the i.r. and U.V. radiation emitted from the source [45]. Roxburgh [46] gave inform- ation on the use and manipulation of filters in the Xenotest 150 to reduce variability in the U.V. content of the light. Giles ef a1 [47J described simple and inexpensive equip- ment for testing light fastness based on the use of mercury- tungsten phosphor (MBTF) and mercury vapour (MB/U) lamps. Sample holders were designed to allow the necessary e.h. to be obtained. The MBTF lamp gives results which are in good agreement with those obtained with daylight and the xenon arc, this source placing the blue standards in the correct sequence with an average interval-fading factor of 2.1 up to Standard 6. A patent [47a] has described a water-cooled cell for use in this equipment. Accelerated light-fastness testing has been examined [48] by using carbon electrodes such as those employed in cinema projectors together with a lens and a means of cooling h e samples. An exposure time of 30 h in this apparatus was similar 72 REV. PROG. COLORATION VOL. 6 1975 in effect to 500 h in a carbon arc. Another procedure was to concentrate the sun’s rays by means of a lens; with this Heliotest device [49] a 25-fold increase in light intensity was obtained. The MB/U source developed by Giles is also claimed [47] to be suitable for rapidly grading materials of high fastness. Rapid methods of testing fastness to light and weathering have been reviewed [50]. It is interesting to note that, of fifteen lamps mentioned for light-fastness testing [5], only two can be operated at the recommended e.h. Work of a theoretical nature has been undertaken but little has been published regarding the direct comparison of results obtained from different fading lamps and the necessary statistical analysis. Four papers [ 5 1 ] contain tables comparing the results obtained from the xenon arc and other sources. An analysis of these results indicates that both the carbon arc and the xenon arc give similar results to daylight, slightly better correlation being obtained with the carbon arc. With both lamps, approximately 15% of all results are one grade or more different from the daylight figures. Friele and Selling obtained better correlation between daylight and the xenon arc when an e.h. of 30% was used with dyeings on synthetic-polymer fibres which had previously given poor correlation between daylight and carbon-arc results. Zukriegel [ 5 2 ] obtained anomalous results with wool- acrylic blends when comparing xenon-arc and daylight testing. Park and Davis [53] compared the MBTF source with daylight and the xenon arc for the major dye-fibre combinations. Excellent correlation was obtained with dyes on wool and nylon, although some anomalies were found with other dye-fibre systems, these being no greater for the MBTF source than with the other sources. Further experiments [54] resolved most of the anomalies. Hindson and Southwell [ 5 5 ] exposed patterns to daylight in Melbourne (Australia) and to radiation from the carbon and xenon arcs, but their results failed to support the accepted view that daylight and xenon arc results correlate any better than daylight and carbon arc results. It was suggested that it may not be essential to use a light source of similar spectral distribution to daylight provided that similar results can be obtained. The same authors found [56] that the MBTF was a satisfactory standard fading source, correlating closely with daylight and the carbon arc. It was claimed that the source is now being widely used despite some anomalous results with sewing threads caused by the presence of fibre finishes. Park and Smith [57] compared a number of fading sources and obtained good correlation between daylight, xenon arc, carbon arc and the MB/U source with water-cooled cells. Differences in results were found between two xenon lamps owing to variations in operating conditions. Light-fastness Standards Two papers [58] describe the historical development of the blue wool standards. Ricketts [59] found by visual assessment of the blue standards after carbon-arc exposure that Standards 1-6 had an interval fading factor of 2. The fading rates of the standards were found [60] to be different in industrial and rural areas, this being explained by differences in r.h. and temperature. Since fading also occurs in winter, it is not necessary to limit exposures to summer months. Rawland [61] confirmed that fading may be seasonal and that the average interval fading factor of the standards is 2 but that there is a range of energy values for any one standard. The average spacing of the standards was found by Jaeckel et al. [62] to be 2.5 and not 2 in daylight but they were irregularly spaced and there appeared to be a seasonal factor. McLaren [63] found that Standard 6 was 1.6 times as fast as Standard 5 and that Standard 7 was 4.2 times as fast as Standard 6. increasing the sample size increases the ease but not the accuracy of assessment [62] . Friele [64] measured the amount of light energy (in langleys) required to produce predetermined degrees of fading of blue standards 1-7. The light energy required and the colour change obtained vary with the time of year and English testing stations gave much lower average langley units than European stations. Twice as much energy was required in Xenotest 150 exposures to reach the same degree of fade as that required in daylight. In addition, the fading behaviour in the Xenotest of several British and German standards was compared with the original IS0 Blue Standards, the greatest discrepancies being found with Standard 7. It has been found [65] that ‘just appreciable fading’ of AATCC LA wool standard, using both visual and instrumental techniques, is equivalent to about 3 NBS units of colour difference or Grade 4 on the grey scale. This degree of fading is produced in 14 hours in the NBS master carbon-arc lamp or in 1 1 NBS standard fading hours. The relationship between the IS0 blue standards 1-8 and the AATCC standards L2 to L9 has been given [66]. The major difference between the two sets of blue wool standards is that the IS0 standards are each produced with single dyes that differ in fastness whereas the AATCC standards are produced by blending different amounts of wool dyed with a fugitive dye (Erio Chrome Azurole B) and a fast dye (Indigosol Blue AGG). To overcome the problem of the unequal spacing of Standards 5 , 6 and 7, Stead [67] suggested that a new Standard 6 should be used, based on a 5% dyeing of Serisol Blue 4GLS (C.I. Disperse Blue 58) on polyester fibre a t 125°C. A further anomaly with one batch of the blue standards has been pointed out [68], namely that Standards 6 and 7 had the same fading rate when the MB/U source was used, although not with the MBTF lamp. When treated in boiling water with or without the addition of a reducing agent, Standard 7 faded at the correct rate, suggesting that the effect may be due to traces of oxidizing agent remaining after the application of the solubilized vat dye used to produce this standard. The difficulties of assessing light fastness above Standard 7 or 8 have been mentioned [69] and a joint SDC-OCCA committee suggested [70] that light-fastness testing of materials faster than Standard 8 be based on the successive exposure of Standard 7. A number of workers have suggested alternatives to the use of the blue standards. It was claimed [71] that greater accuracy could be obtained by using photoelectric measure- ment of light exposure and using an assessment based on the number of ‘just noticeable differences’ in colour from the original pattern. Mudd [72] designed a simple fading lamp using a 150-W xenon lamp in which the light falling on the pattern could be maintained at constant intensity so that the light fastness could be precisely expressed in terms of the amount of light (kilo-ft-candle-hours) required to fade the pattern. Schmitt [73] indicated that the langley system was superior to the sun-hour system and claimed that the AATCC standards were superior to the IS0 standards. REV. PROG. COLORATION VOL. 6 1975 73 Carbon-arc lamps can be calibrated using paper dyed with Benzo Azurine G [74]. This paper is exposed with the patterns and compared with previously prepared standards. Clock hours can thus be converted to ‘standard fading hours’. Correlation between the fading of the blue wool standards, clock hours and standard fading hours is influenced by the age of the light source, and to overcome confusion a new term - twenty AATCC fading units - has been introduced. This is defined [75] as the exposure required to produce a ‘just appreciable fade’ (Grey Scale grade 4) on the AATCC blue wool light-fastness standard L4. The other blue wool standards can be similarly defined in terms of AATCC fading units, which are independent of clock hours, langleys, etc. Friele [76] proposed a method which depends on the measurement of relative radiation and the use of Standard 5 to calibrate the new scale. Light-fastness ratings are obtained by means of a contrast scale after exposure times that are indicated by the calibrated radiation meter. Loepffe [77] reported the results of numerous tests carried out between 1965 and 1970 in an attempt to introduce measurement of daylight intensity in langley units. The degree of variation in the results of the pyranometer measurements were such that the project was abandoned. Heuberger [78] reviewed developments concerning the light fastness of fluorescent brighteners, including recent attempts to establish white standards and scales for assessing changes in whiteness. Weathering Two papers [79] have reviewed the test for fastness to weathering, the principal findings being that outdoor results depend on location and season, that outdoor and lamp methods can be used and that the blue standards can be utilized for assessment provided that they are exposed under glass along with the patterns. A more recent review [80] has compared the types of actinometer used. Weathering is now included in the relevant British Standard [ l l ] and it was agreed in Paris [9a] to include a filter for u:~. radiation and to protect the blue standards by window glass in the xenon-arc method. The Effects of Ozone Salvin [81] reported that ozone and oxides of nitrogen present in the atmosphere could affect light fastness. These gases themselves will fade dyes [82], the effect being greater at high humidities, with disperse dyes being the most susceptible; durable-press finishes accelerate the effect. A test procedure was developed in which specimens are suspended in a chamber where a humidity of 85-90% can be maintained, ozone being generated and passed through the chamber. The samples are subsequently assessed against a fading control, this being a dull green dyed with disperse dyes on nylon. This test has now been accepted as an AATCC standard [83]. Beloin [84] found significantly greater fading in urban districts, the main causes of fading being sulphur dioxide, oxides of nitrogen and ozone. A later study [85] confumed these findings and indicated that increase in humidity and temp- erature increased the rate of fading but that this was not related linearly to the exposure time. Gas-fume Fading The history of gas-fume fading, with references to the original work, and the associated tests has been covered in a number of papers [e.g. 861. Various aspects of the IS0 tentative test were examined [87] and an improved apparatus was described. Preliminary neutralizing had little effect on many of the dyes tested but about 40% of them were affected by the e.h. Better reproducibility was obtained by using gas from cylinders because of the better pH control of the samples, although the composition of the oxides of nitrogen had little effect. Fastness to Washing The series of IS0 wash tests [5] is well established and it is many years since the variables in the test were elucidated [88]. i n brief, the IS0 tests are a series of soap-based procedures of increasing severity intended to cover the range from hand washing up to high-temperature washing of cellulosic materials. These tests are extremely useful for screening dyes but require careful interpretation by experi- enced users when considering fitness for purpose of dyed materials. A British Standard, however, specifies [89] the tests to be used for apparel, furnishing and household textiles, excluding wool. The washing tests developed in the U.S.A. were enumerated by Sylvester [ 121 . Originally, four tests were used but these were considered to be too mild and the ‘accelerated’ tests were established to predict the loss in colour and abrasive action due to washing by hand up to mechanical washing in presence of chlorine. Changing from soap to anionic or nonionic detergents did not alter the loss in colour significantly. The ‘A’ tests are designed to produce in 45 min the effect of five repeated washings of the appropriate nature in regard to loss of colour [90]. The accelerated tests were reviewed [91] by comparing the results obtained with a wide range of fabrics both in the laboratory tests and in different types of domestic washing machine after 5 washes at 1.00, 120, 140 and 160°F. The laboratory tests gave a reasonably close prediction of the fastness to be expected on repeated domestic washing in regard to loss of colour. Domestic washing at 120’F. generally gave results intermediate between tests IIA and IIIA while some materials were faster to washing at temperatures higher than those covered by test IIIA. These tests do not cover staining. Stetson [92] questioned the relevance of current testing procedures since commercial laundering differs from home laundering. Lenz [93] stated that washing-fastness tests should be based on consumer washing habits. He used a test to determine the suitability of materials for sale based on the IS0 2 conditions but using 5 g/l of a detergent containing 20% perborate, the white adjacent fabrics being the same as the test piece, cotton and heat-set nylon 6. Blackburn [94] underlined the suitability of the IS0 1 to 5 washing tests plus the peroxy test for selecting dyes and argued that these tests must be retained by colour users. However, further tests may be required for appropriate care-labelling. It has so far been impossible to find alternative tests but perhaps the American tests should be examined [95]. Hine and McPhee [96] suggested that synthetic detergents should be used since soap does not give a true indication of the effects of domestic laundering because the degree of staining is altered by changing the detergent, although change in colour seems to depend on detergent type to much less extent [90]. A test has been developed [97] based on the use of 0.75 g/l sodium perborate and 4.25 g/l of a washing powder which was approved by the European Council of Domestic Appliance 74 REV. PROG. COLORATION VOL. 6 1975 Manufacturers (Ceced). While developing tests to evaluate cloths intended to meet Superwash (IWS) standards, Smith [98] found that tests based on the IS0 2 and 3 tests were unsuitable. Dyeings could pass five IS0 3 tests but fail in a machine-washing test. The test adopted, which correlates with machine washing, is based on the use of 3.75 g/1 heavy-duty, low-foaming detergent plus 1.25 g/l sodium perborate, and is carried out for 45 min at a liquor to goods ratio of 50: 1, at 50°C., using shrink-resist- treated wool, nylon and cotton as adjacent fabrics. Since most detergents available in the U.K. contain sodium perborate, it would seem likely that washing tests will be developed incorporating a compound of this type. A new draft test for fastness to commercial and domestic laundering is to be issued, in which the AATCC detergent without fluorescent brightener will be specified [9a]. Scales [99] suggested the use of nylon adjacent fabrics in all washing tests because of the high substantivity of this fibre for dyes of a large number of classes. The degree of staining on nylon is, however, influenced by the chemical type (e.g. nylon 6.6 v. nylon 6), the physical characteristics of the fibre (i.e. whether texturized or flat continuous-filament) and the setting process used. The standard reference wool fabric for use in fastness testing has been specified [ loo] and a multifibre adjacent cloth has also been developed [ lo l l in which the nylon used has intermediate staining properties. Dry Cleaning The factors which influence fastness to dry cleaning are the solvent, mechanical action and the detergent. A number of test methods were compared [I021 but none was found to be satisfactory, mainly owing to their failure to reproduce the necessary mechanical action. A new method was developed in which the test specimen is placed in a cotton bag together with steel discs and then shaken in 200-ml perchloroethylene a t 30°C., for 30 min. The use of adjacent materials to assess staining can give misleading results, so assessment should be confined to colour change and the discoloration of the liquor. Thirteen different test methods for dry-cleaning fastness were evaluated [ 1031, the effect of changing various factors being assessed on a range of dyeings and prints on various fibres. Fastness ratings were high and changes in test con- ditions had little effect. Dyeings on polyester gave the lowest ratings and tended to be more sensitive to trichloroethylene than to the other solvents used. A test based on that described by Rhodes [ 1021 was adopted [ 1041 as AATCC 132- 1969 (now 132-1973). Rubbing Fastness A rotary rubbing apparatus has been developed [ 1051 which gives similar results to the oscillating type (Crockmeter) but which is useful for small test samples, although colour trilnsfer seems to be greater at the edges of the rubbing fabric. Bigler [ 1061 has described various tests, and a new machine I 107 I has been designed which enables rubbing-fastness tests to I ic carried out on carpets in situ,carpet yarns and cuttings: a drat'[ test procedure has been published [ 1081 . Carpets An investigation was undertaken [lo91 to assess the nccd 1'01 tests for determining the fastness of carpets to coiiiiiioii agencies. I t was decided that special tests for fastness to acid. alkaline storage, heat, reducing agents and urine were not required and that the effects of the latter are similar to that of salt. Light fastness should be tested according to BS 1006. Tests were developed and subsequently published [6] 'for fastness to salt, shampooing and water. A standard has been issued [ 11 01 for the testing of carpets to determine their performance. The carpet test for shampoo- ing was criticized [ 1 1 11 as being unsatisfactory for piece-dyed carpets, since dyes which failed the test had been found satisfactory in use. In reply, it was stated that the tests were not designed to set commercial standards based on pass-fail testing. Fastness to Pleating and Setting A test was devised [112] for determining fastness to steam pleating, this being based on wrapping the sample and adjacent materials on a roll and steaming in a pressure cooker or jacketed steamer. Five steaming conditions (later reduced to three) were chosen to cover all fibres. Good correlation was obtained between the test and practical pleating results, the test giving uniform staining of adjacent materials. A similar test was adopted [113] as AATCC 131-1969. Fastness to dry-heat pleating and setting is determined [I141 by placing the sample and adjacent fabrics between aluminium foil in a hinged holder and then placing the holder in molten metal at the required temperature for 30 s, three temperatures being used. Good agreement was obtained between results obtained with this test, the BASF precision- heating press and the Rhodiaceta Thermotest. Colour fastness to the chemical setting of wool can be determined [ 11 51 by subjecting the sample and adjacent materials to steaming in a press after the sample has been sprayed with a 5% aqueous solution of MEASAC. An untreated sample is also steamed for comparison. An apparatus for testing fastness to thermo- fixation has been described [ 1161 and a further contact-heat apparatus marketed [ 1 171 . Fastness to Water The test for fastness to water has been widely used on wool, especially in connection with the Woolmark (IWS) specific- ation. A number of test methods and the various factors in the tests were examined [ 1181. To obtain reproducible results, the test must be carried out under well-defined conditions of temperature, time and applied weight. It was recommended that the pH of the test solution should be specified in the standard method. Perspiration The work of the Society of Dyers and Colourists in developing tests for fastness to perspiration has been reported [ 1 191 . The effect of natural perspiration on dyes, especially copper complexes, is due to its amino-acid content, histidine being the 1iiost reactive in removing the metal. The development of perspiration tests on both sides of the Atlantic has been rcviewed [ I201 . Gobeil and Mueller [ 121 ] have compared laboratory results with those obtained during wear. They concluded that the alkaline test does not predict accurately tlic staining which may occur in wear. With wool the test gives iiiorc severe staining while the reverse is true for acetate. With nylon. the degree of staining on nylon is similar in alkaline and acid tests. The acid test is said to predict wear performance accurately. REV. PROG. COLORATION VOL. 6 1975 75 Bleaching The development of methods for assessing fastness to bleach- ing by chlorine and by peroxide has been reviewed [ 1221 . A test for fastness to peroxide bleaching has been described [ 1231 in which a liquor ratio of 1 : 1 is employed to simulate pad-roll and continuous processing. Assessment The use of the Grey Scales in fastness testing is now well established [4] and various papers [124, 125, 1261 have traced their development. Nine-step grey scales in a fold-out format are now available [ 1271 which give the same accuracy and reproducibility as the former slide-rule type. The Adams-Nickerson ANLAB [40] formula has been used [128] to assess colour fastness. Good correlation of results was obtained between visual and instrumental methods where ratings were made against the Grey Scales but not with the blue standards in the light-fastness test, where a graphical approach was necessary. The form of the sample used did not affect the fastness rating by more than a half-grade on the Grey Scale in the water and perspiration tests [129]. Poles [ 1301 found that, with a number of observers, fastness ratings varied up to one grade and this degree of difference could be obtained by the same observer at various times [see also 29 and 301. A statistical evaluation of variations in the assessment of light fastness according to the Woolmark specification showed [ 13 1 ] that three observers achieved much better accuracy than one, even if one of them differed systematically by a half-grade in either direction. The use of five observers is seldom justified. Since the fastness of a dye is a function of the depth of dyeing, it is usual to specify standard depths and these have been illustrated in a number of hues on matt and bright fabric [132]. Care Labelling A review of this nature would be incomplete without mention of fastness testing in relation to care labelling. An inter- national fastness label is thought [ 1331 to be desirable but it must be based on reproducible test methods. In any case, the dictates of fashion often result in fastness being a secondary consideration. The various types of labelling scheme have been reviewed [134]. it has long been the policy [135] for the Society of Dyers and Colourists to develop test methods but not to participate in establishing performance standards. Because of changes in fibres, processing routines, finishing procedures and washing practice, test methods and perform- ance standards should be continuously reviewed. Investigations were carried out [ 1361 on IS0 tests for fastness to washing, dry heat and shampooing, and on laboratory methods of determining dimensional stability and crease recovery, to see how the results compared with actual performance. The evidence on washing tests indicated that a large co-operative investigation would be worth while. Changing the liquor ratio did not affect the colour change but the staining of adjacent materials increased at low liquor ratios. The results were affected by the use of soap or detergents, the concentration of which influences the results, heavier staining sometimes being obtained at lower concentrations. The staining of adjacent cloths after 25 washes in various machines was similar or less than in the equivalent IS0 test. It seems that loss in depth is the main criterion in tests in the U.S.A., whereas the British consumer is more worried by staining; this factor comes to light in many of the investiga- tions which have been carried out on washing. In describing the HLCC scheme, Handley [137] pointed out that the majority of fabrics could be covered by eight washing procedures. In each the temperature, amount of mechanical agitation and water-extraction method are defined. A new series of HLCC symbols has been announced [ 1381. Care labelling in Europe, the U.K. and Canada has been summarized and the development of the various schemes described (1391. The variables covered include washing (i.e. whether by hand or machine, and wash temperature), bleach- ing, drying, ironing and dry cleaning. Staples [ 1401 discussed labelling in regard to washing and dry cleaning. A labelling scheme requires that the dyer and finisher carry out the necessary quality-control testing, preferably on the complete garment assembly. Correlation is desirable between the standard washing tests and the performance in home launder- ing, although this seems unlikely at present. There is also a need for a standard synthetic detergent. Conclusions The technology of fastness testing is now well established but there is scope for the consolidation of the information available, especially for the two more important tests, namely light and washing, where contradictory evidence exists. There are demands for consumer-orientated tests and a rationaliza- tion of tests developed by many retail organizations. Finally, there are still a large number of tests used at national level which are at variance with the I S 0 methods. This has been indicated by Schlaeppi [9] , for example, by comparing the IS0 and AATCC equivalent test methods, although BSI and IS0 tests correspond. 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