Influence of embossing parameters on colour changes and shape retention behaviour of vegetable‐tanned leathers

Abstract Vegetable‐tanned calf leathers are highly esteemed for their aesthetic qualities, durability and shape retention, making them particularly suitable for high‐end leather goods such as bags, belts and wallets. Some embossing processes are applied for visual purposes in the production of these leather goods. This study investigates the effects of different vegetable‐tanning agents and varying embossing conditions (temperature and duration) on the shape retention and colour change behaviour of calf leathers. For this purpose, hydrolysable tannins (valonia and chestnut) and condensed tannins (mimosa and quebracho) were incorporated into the tanning process and their effects on the leather's shape retention after embossing and thermal discoloration were analysed. The results provided valuable insights into the role of tannin type in determining post‐emboss leather properties. Colour analysis revealed that both the tanning composition and processing conditions, including temperature and embossing duration, significantly influenced the final appearance of the leather. Notably, elevated embossing temperatures further intensified colour variations. The results of shape retention after embossing indicated that higher temperatures and extended embossing durations improved the durability of embossed patterns, ensuring long‐term stability. These findings contribute to a better understanding of the relationship between type of vegetable tannin and the hot press behaviour of leather, aiding in the selection of suitable tannins for optimising colour stability and shape retention in embossed leathers.