This guide is a support for textile industry players, to improve commmunication about chemicals and raise the possibility for well-informed substitution work. It focuses on subsitution of highly fluorinated substances, also known as per- and polyfluoroalkyl substances (PFAS), offering textile buyers a deeper understanding about water repellence and the associated chemistry. The guide can be used as a starting point for your chemicals management and substitution work, with many links to other information sources. We recommend using the Table of Contents below as a navigational tool, to start filling any knowledge gaps and expand your reading from there.