Spectrophotometric and colorfastness data for iron oxide (rust) dyeing on five textile substrates

This dataset contains raw spectrophotometric data (Datacolor 650 instrument output), colorfastness test records, and rubbing fastness measurements supporting the manuscript "Can Rust Dye Your Clothes? A Systematic Study of Iron Oxide as a Natural Dye on Five Textile Substrates" submitted to Royal Society Open Science (RSOS-261093). Data include %R values at 360–700 nm, K/S values, CIE Whiteness Index, CMC colour difference (ΔE) under three illuminants, and Grey Scale colorfastness ratings for five textile substrates under four pretreatment conditions.