The rate of photoyellowing, when wet, of wool cloth bleached conventionally with hydrogen peroxide and then with stabilized sodium dithionite depends on the pH of the dithionite bleaching bath. Between pH 3.5-7.5, the lower the pH. the higher the lightfastness. The enhanced photostability of damp fabric which has been dithionite-bleached at pH 3.5 is not fast to washing. Indeed, when washed under certain conditions, the wet wool becomes particularly sensitive to sunlight yellowing. These effects become very apparent on fabric treated with a fluorescent whitening agent. Cloth treated with sodium metabisulfite behaves similarly. The photostability of dry wool is not affected by bleaching or washing conditions. The lightfastness on wet and dry cloth of a selection of commercial fluorescent whitening agents is compared here.
Get full access to this article
View all access options for this article.
References
1.
Asquith, R.S. , Falkingham, A.H., and Pearcy, M.N., Yellowing and Bleaching of Wool Fabric Using a Xenotest 450, J. Soc. Dyers Colour.86, 367-368 ( 1970).
2.
Fallaw, D.C. , and Tucker, D.J., Optical Brightening Agents on Wool, Textile J. Aust. 40, 46-48 (1965).
3.
Frommelt, C. , Bleaching and Fluorescent Whitening of Wool , Bayer Farben Rev.25, 80-83 (1975).
4.
Ganz, E., Whiteness: Photometric Specification and Colorimetric Evaluation, Appl. Optics15, 2039-2058 (1976).
5.
Graham, D.R. , and Statham, K.W., The Photochemical Oxidation of Wool in the Presence of Fluorescent Compounds, J. Soc. Dyers Colour.72, 434-439 (1956).
6.
Griesser, R., Instrumental Measurement of Fluorescence and Determination of Whiteness: Review and Advances, Rev. Prog. Color.11, 25-36 (1981).
7.
Gruen, L.C., and Inglis, A.S., Studies in Wool Yellowing, Part XXI: Further Studies on Wool Fabrics Treated with Fluorescent Brightening Agents and Thiourea-Formaldehyde, Textile Res. J. 38, 509-517 (1968).
8.
Holt, L.A., Milligan, B., and Wolfram, L.J., Fluorescent Whitening Agents, Part V: The Use of Reducing Agents for Retarding the Yellowing of Fluorescently Whitened Wool by Sunlight, Textile Res. J. 44, 846-851 (1974).
9.
Holt, L.A., Milligan, B., and Wolfram, L.J., Fluorescent Whitening Agents, Part VI: The Whitening of Wool by Surface Application of Whitener Polymer Solutions, Textile Res. J. 45, 257-264 (1975).
10.
Holt, L.A., and Milligan, B., Evaluation of the Effects of Temperature and UV-Absorber Treatments on the Photodegradation of Wool, Textile Res. J.54, 521-526 (1984).
11.
Launer, H.F. , Effect of Light upon Wool, Part IV: Bleaching and Yellowing by Sunlight, Textile Res. J.35, 395-400 (1965).
12.
Leaver, I.H. , Studies in Wool Yellowing, Part XXII: ESR Investigation of the Action of UV Radiation, Textile Res. J.38, 729-734 (1968).
13.
Levene, R., and Knoll, A., Determination of Fluorescent Whiteness: Experience in Using Linear Whiteness Formulae, J. Soc. Dyers Colour. 94, 144-149 (1978).
14.
Levene, R., and Lewin, M., ch. 3 in "Handbook of Fiber Science and Technology," vol. 1B, M. Lewin and S. B. Sello, Eds., Marcel Dekker, New York, 1984.
15.
Levene, R., ch. 4 in "Handbook of Fiber Science and Technology," vol. 1B, M. Lewin and S. B. Sello, Eds., Marcel Dekker, New York, 1984.
16.
Lewis, D.M. , Applying Shrink Resist Polymers to Wool Fabrics at Room Temperature Using Pad-Store Methods, Textile Res. J.52, 580-586 (1982).
17.
Maclaren, J.A., and Milligan, B., ch. 13 in "Wool Science, The Chemical Reactivity of the Wool Fibre ," Science Press, Marrickville, NSW, 1981.
18.
Milligan, B. , and Tucker, D.J., Studies on Wool Yellowing, Part III: Sunlight Yellowing, Textile Res. J. 32, 634-640 (1962).
19.
Milligan B. , and Tucker D.J., Studies on Wool Yellowing, Part V: Effect of Buffer Pretreatment on the Sunlight Yellowing of Wool, Textile Res. J. 33, 487-488 (1963).
20.
Milligan, B., Sunlight Yellowing of White Wool: A Complex Problem, in " Proc. 6th Int. Wool Textile Res. Conf., Pretoria," V, 1980, pp. 167-181.
Savige, W.E. , Studies in Wool Yellowing, Part XVIII: Processes for Retardation of Sunlight Yellowing of Fluorescent-Brightened Wool, Textile Res. J.38, 101-102(1968).
23.
Tucker, J.E. , Reduction of Sunlight Yellowing of Wool Fabric Treated with Fluorescent Brightening Agents, Textile Res. J.39, 830-835 (1969).
24.
Valk, G., Sulphitolysis and Hydrosulphitolysis of Wool, in " Proc. 3rd Int. Wool Textile Res. Conf., Paris," II, 1965, pp. 375-386.
25.
Van Rensburg, N.J.J., Reductive After-Treatments of Peroxide-Bleached Wool, Textile Res. J.38, 318-320 (1968).
