Comparison of Colourfastness in Printex-Finished Cotton Fabrics across Three Washing Exposures: Key Soap Versus Standard Soap

Aim: This laboratory study compared the colourfastness of three black-and-white 100% cotton Printex fabric finishes (plain, embossed, and plissé) after three washing exposures with Key Soap and a Ghana Standards Authority reference soap (Standard Soap). Methodology: The colourfastness component comprised 18 specimens representing three fabric finishes, two soap systems, and three washing exposures corresponding to 30, 60, and 90 min. Colour change was assessed against unwashed controls using the ISO Grey Scale for assessing change in colour. Three observers evaluated the washed and control specimens. The primary interpretation was descriptive. The one-way ANOVA values reported in the original analytical summary are retained as exploratory because the colourfastness subset contained one specimen per finish × soap × washing-duration condition. Results: With Key Soap, all finishes were rated 4–5 after 30 min; after 60 min, the embossed finish declined to 4; and after 90 min, the plain and plissé finishes were rated 4 while the embossed finish was rated 3. Under the study's predefined pass criterion of at least 3–4, only the embossed finish under Key Soap at 90 min fell below the criterion. With Standard Soap, all recorded ratings remained at or above 3–4 across the three washing exposures, although the pattern was not strictly monotonic. Exploratory ANOVA values were p = .42 for Key Soap and p = .03 for Standard Soap; these p-values are not treated as confirmatory evidence because independent replication at each experimental cell was not available. Conclusion: Within the tested fabrics and laboratory conditions, colour retention varied with fabric finish, washing exposure, and soap product. The most pronounced colour loss occurred for the embossed fabric washed with Key Soap for 90 min. The findings support product- and finish-specific care recommendations, while broader claims about detergent chemistry or general detergent superiority require replicated testing and direct chemical characterization.