the so-called Wet Blue, wet blue leathers ready for further processing. Retanning gives the leather the structural characteristics of softness, grain firmness, elasticity and fullness. In large rotating cylinders - the buttons - solutions of water and chemical reagents are introduced, with the utmost attention paid to saving water and using biodegradable products to reduce environmental impact. The dyeing process gives the leather an initial desired colour, thanks to water-soluble dyes that penetrate deep into the leather evenly.