Vol.:(0123456789) 1 3 Fibers and Polymers (2023) 24:3221–3233 https://doi.org/10.1007/s12221-023-00296-4 REGULAR ARTICLE Online ISSN 1875-0052 Print ISSN 1229-9197 Color Shade Extension of Reseda luteola L. Natural Colorant on Wool Textiles via Binary Combination of Metal Salts: Colorimetric and Fastness Studies Siyamak Safapour 1  · Majid Mazhar 2  · Saiedeh Abedinpour 2 Received: 18 June 2022 / Revised: 16 November 2022 / Accepted: 28 December 2022 / Published online: 31 July 2023 © The Author(s), under exclusive licence to the Korean Fiber Society 2023 Abstract Reseda luteola L., commonly known as weld, is an important source of yellow natural dye used for dyeing the wool textiles since ancient times. In this study, to develop the color shades of weld on wool textiles, single and binary combinations of eight metal mordants, i.e., Al, Fe, Cu, Co, Zn, Sn, Ni, and Cr were explored using the premordanting method. Depending on the type and nature of mordant in the mixture, substantial variations in the color shades, lightness, color strength, and fastness of the samples resulted. In addition to metal mordants that individually improved color strength, color fastness and produced various color shades, binary mordanting showed several novel features in terms of the development of new color shades, the synergistic efect of dye uptake (color strength), and color fastness, etc. Furthermore, several rare or unique shades of high-cost and toxic mordants, such as Cr, could be reproduced using alternative binary low-cost and non- or less toxic mordants, such as Fe and Cu. Keywords Natural dye · Reseda luteola L. · Metal mordant · Wool · Color shade · Color fastness 1 Introduction The majority of industrial products are frst inspired by nature, and then their improved characteristics are expanded by researching and examining man-made products during a long period of time. The dyeing industry is not an exception to this rule. Hence, in the mid-nineteenth century when W. H. Perkin introduced “Mauveine” as the frst synthetic dyes, colorants obtained from renewable resources like insects, fungi, minerals, and some parts of plants, such as roots, leaves, barks, skins, fowers, fruits, and shells of plants with- out any chemical processing were used exclusively as color- ants [1–3]. Due to their lower cost, quick synthetic process, increased fastness, durability, broad range of color diver- sity, capacity to dye synthetic textiles, and availability on a big industrial scale, synthetic dyes subsequently expanded quickly [4, 5]. After a while, the side efects of production and consumption of synthetic dyestufs were identifed as serious problems for human health and environment [6–8]. The dyeing industry is one of the largest industries pro- ducing toxic efuents [9, 10]. In recent decades, the world community is moving towards cleaner alternative technolo- gies and materials to protect the environment as much as possible. So, natural colorants as alternatives to synthetic dyes due to the biodegradability, eco-friendly character, less toxicity, sustainable nature, etc., would help the world community to achieve a green and clean world [11–13]. In several industrial felds, natural dyes made from plants have been used for millennia to color products. The family of favonoids that produces yellow hues includes a signifcant portion of these natural dyes [14]. Their general structure is based on 2-phenyl benzopyrone, which is colorless. But, its poly-hydroxy derivatives (favonols) by absorbing UV and blue part of the visible region show yellow colors [15]. In addition to coloring potential, natural colorants show sev- eral functional properties multifunctional properties, such as * Siyamak Safapour s.safapour@tabriziau.ac.ir Majid Mazhar m.mazhar@azaruniv.ac.ir 1 Key Laboratory of Advanced Eco-Dyeing and Functional Finishing of Textiles, Faculty of Carpet, Tabriz Islamic Art University, P. O. BOX 51385-4567, Tabriz, Iran 2 Department of Chemistry, Faculty of Basic Science, Azarbaijan Shahid Madani University, Tabriz, Iran