ROSA, JORGE M.MELO, CAMILA G.PEREIRA, MARIA da C.C.BORRELY, SUELI I.2021-07-292021-07-292021ROSA, JORGE M.; MELO, CAMILA G.; PEREIRA, MARIA da C.C.; BORRELY, SUELI I. Reactive Blue 21 exhaustion degree investigated using the surface response methodology as an auxiliary tool in cotton dyeing. <b>Journal of Natural Fibers</b>, v. 18, n. 4, p. 520-530, 2021. DOI: <a href="https://dx.doi.org/10.1080/15440478.2019.1636739">10.1080/15440478.2019.1636739</a>. Disponível em: http://repositorio.ipen.br/handle/123456789/32069.1544-0478http://repositorio.ipen.br/handle/123456789/32069Response surface methodology was used to investigate the influences of sodium chloride (NaCl), soda ash (Na2CO3), and sodium hydroxide (NaOH) concentrations on cotton and the degree of exhaustion (DE) of Reactive Blue 21 dyestuff (RB21), as well as to optimize dyeing conditions. A 23 central composite and rotational design was used as a support to carry out 17 dyeings with RB21 on a 100% knitted cotton substrate. NaCl, Na2CO3, and NaOH concentrations were used as factors. Responses comprised color strength (K S‒1) and the DE. The results indicate that a square model was the best fit. This model was able to increase both K S‒1 and DE values, with the colorfastness to water and rubbing carried out with supplier’s formulation recipe. This study demonstrates that the use of the response surface methodology in color matching can contribute to the textile industry in the prediction or assessment of formulations for a specific color.520-530openAccessdyescottonexhaust systemscolorsurfacesArtigo de periódico41810.1080/15440478.2019.1636739https://orcid.org/0000-0002-9692-553986.5477.00