100 JSDC VOLUME 115 MARCH 1999

The colour fastness of dyed fabrics to activatedoxygen bleach-containing detergents: aninternational interlaboratory trial

Duncan Phillips, Geoff Bevan*, John Lloyd†, Robin Hall‡ andJurgen Hoffmeister§

Dept of Textiles, UMIST, PO Box 88, Manchester M60 1QD, UK

*Lever Brothers Ltd, PO Box 69, Port Sunlight, Merseyside L62 4ZD, UK†Unilever Research Laboratory, Quarry Road East, Bebington, Merseyside L63 3JW, UK‡Procter and Gamble Ltd, Whitley Road, Longbenton, Newcastle upon Tyne NE12 9TS, UK§Henkel KGaA, WEW-Waschtechnik, Henkelstrasse 367, D-40191 Dusseldorf, Germany

The UK-TO single wash test procedure, developed to be diagnostic of the oxidative bleach responseof dyed articles to repeated washing in activated oxygen bleach-containing detergents, has beensubjected to extensive interlaboratory trials. The results indicate that both its repeatability andreproducibility are fully acceptable for the purpose of interlaboratory comparisons.

INTRODUCTIONThe development of a diagnostic single wash test toidentify those dyed cotton fabrics that are susceptible to theactivated oxygen bleach present in domestic detergentproducts was described in a previous article [1]. Followingsuccessful interlaboratory trials in the UK [2], theprocedure was adopted as a British Standard: BS 1006‘UK-TO Colour fastness to domestic laundering –oxidative bleach response’ in May 1998.

Prior to submitting the test procedure for adoption asan ISO standard, an international interlaboratory trial wasorganised through the Fastness Tests Committee of theSociety of Dyers and Colourists. A set of dyed fabrics wastested in laboratories in Germany, Japan, Spain, Sweden,Switzerland, the UK and the USA. This paper describesthe results obtained from the study.

TEST METHODAs in the UK trials, the main objective of the internationalinterlaboratory trial was to assess both the repeatability ofthe test method within a single laboratory and itsreproducibility between different laboratories.

Eleven of the twelve fabrics used were dyed at a level of4% owf, the other being a pale–medium (1%) depth of CIReactive Black 5 (Table 1).

Participants in the trial were provided, through theSociety of Dyers and Colourists, with the BS 1006 UK-TOtest procedure [3], samples of dyed fabrics, ECEnon-phosphate reference detergent base [2], TAED (tetra-acetylethylenediamine) and sodium perborate tetra-hydrate to enable them to carry out three replicatewashes. The colour fading arising from the application of

Table 1 Test fabrics

Fabricno Substrate Dye

1 Polyester CI Disperse Red 60 2 Polyester CI Disperse Blue 79 3 Cotton CI Vat Blue 4 4 Cotton CI Sulphur Red 10 5 Cotton CI Sulphur Black 1 6 Cotton CI Reactive Red 2 7 Cotton CI Reactive Red 195 8 Cotton CI Reactive Red 228 9 Cotton CI Reactive Orange 1610 Cotton CI Reactive Black 5 (1%)11 Cotton CI Reactive Black 5 (4%)12 Cotton CI Reactive Blue 225

the test procedure was measured instrumentally as CIEL*, C* and H* values to allow a range of colour-differenceequations, e.g. CMC(2:1), and calculated grey scale data(ISO 105:A05) to be employed in the analysis of repeat-ability and reproducibility.

RESULTS AND DISCUSSIONData were returned from 15 laboratories and the meancolour changes (∆E) of the individual fabrics aresummarised in Table 2.

For purposes of the analysis, fabrics were groupedaccording to whether the colour change was greater(seven fabrics) or smaller (five fabrics) than two CMC(2:1)units. A CMC(2:1) value of less than two is equivalent to acalculated grey scale (ISO 105:A05) of four or more, and

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others and was the fabric giving the highest level offading. All participating laboratories agreed with this levelof high fading, but differed in the absolute magnitude.

The overall results for the fabrics grouped on the basisof grey scale data are summarised in Table 4. In order toput these results into context, a laboratory carrying out arobust wash fastness procedure using visual assessmentsas the measure of fading might reasonably be expected toproduce gradings within 0.5 grey scale units in a series ofthree replicate tests. This corresponds to a repeatabilitystandard deviation of 0.289, which is larger than thevalues obtained here. The repeatability of the test methodis therefore within the range that might be expected forwash fastness tests in general.

Regarding the reproducibility of the test procedure, in aparallel international trial of the ISO 105:C06 procedure[4], a reproducibility standard deviation for colour changeof 0.41 was obtained. The estimates for reproducibilityshown in Table 4 are smaller than this figure, indicatingthat the proposed procedure is of a comparable level ofrobustness to that currently obtained from the establishedISO 105:C06 standard test procedure.

CONCLUSIONA single wash test procedure has been developed to beindicative of the oxidative bleach response of dyed articlesto repeated washing in activated oxygen bleach-containing detergents.

The test procedure has been subjected to extensive UKinterlaboratory trials, in which an excellent correlation wasfound between the results from the test procedure andthose after repeated washes in domestic washingmachines. Indeed, the intralaboratory repeatability andinterlaboratory reproducibility standard deviations of thetest were fully acceptable for the procedure to be acceptedas a British Standard, BS 1006 ‘UK-TO Colour fastness todomestic laundering – oxidative bleach response’ in May1998. The results from an international interlaboratory trialof the BS 1006 UK-TO test procedure have shown that itsrepeatability and reproducibility is completely acceptablefor the purposes of interlaboratory comparisons. The testprocedure has been submitted for ISO recognition.

* * *

The authors gratefully acknowledge the assistance of thepersonnel in those countries who participated in thestudy, Dr C Graham (SDC) for her help in organising thetrial and for the advice and continued support of Mr PCollishaw (BASF) and Mr D McKelvey (M&S) in technicaldiscussions.

Table 2 Mean colour change

Colour difference (∆E)

Fabricno CIELAB CMC(2:1) Grey scale A05

1 0.9728 0.4224 4.64237 2 0.6170 0.4140 4.67452 3 2.7555 1.3873 4.19360 4 11.6112 5.5621 1.27091 5 20.1533 17.1861 0.46778 6 9.4414 5.0709 1.93535 7 1.7975 0.8778 4.26418 8 12.3095 4.9458 1.63302 9 8.2378 3.7256 2.1423210 5.3955 4.2535 2.4571511 3.0402 2.8538 3.3508012 0.8090 0.7032 4.55031

Table 3 Individual test fabric repeatabilityand reproducibility standard deviations

Standard deviation

Fabricno Repeatability Reproducibility

Group 1a

1 0.19201 0.35273 2 0.15277 0.21323 3 0.25555 0.39416 7 0.29378 0.4640412 0.19162 0.25893

Group 2b

4 0.59862 1.24024 5 1.91037 3.53182 6 0.47951 0.79148 8 0.35514 0.43339 9 0.42133 0.6976110 0.61735 1.2892011 0.41935 0.80524

a ∆E CMC(2:1) < 2 (grey scale ≥ 4)b ∆E CMC(2:1) > 2 (grey scale < 4)

Table 4 Mean grey scale values and repeatability/reproducibilitystandard deviations

Standard deviation

Groupa Mean grey scale Repeatability Reproducibility

1 4.46500 0.17175 0.259762 1.89390 0.20505 0.35076

a For key see Table 3

corresponds to fabrics giving only very small colourchanges in the test. Results for the repeatability andreproducibility standard deviations, averaged over theparticipating laboratories, are summarised in Table 3.

Test fabric 5, dyed with CI Sulphur Black 1, stands outin respect of having a much higher variability than the

REFERENCES1. D A S Phillips et al., J.S.D.C., 112 (1996) 287.2. D A S Phillips et al., J.S.D.C., 113 (1997) 281.3. BS 1006 UK-TO (May 1998).4. D A S Phillips et al., J.S.D.C., in press.