Effects of drying methods on chrome-tanned leather

The drying operation is a critical leather-making step to attain the required physical properties for leather products. There are various drying methods currently being used today in leather manufacturing. To make quality leather, it is imperative to understand the effects of different drying methods on the physical characteristics of leather. Results from our comparison study showed that the method applied in a drying operation significantly affects the physical properties of leather, particularly area retention and compliance. Observations indicated that toggle drying produces higher area yield, but may result in stiffer leather. One of the important findings from this study is that there is a direct link between grain break and stiffness of leather. Data indicated that stiffer leather often results in poor break. Our research again showed that residual water content is a key factor for softness. Vacuum drying without toggling yields better toughness and softness, but does not significantly improve area yield. We also presented a dimensionless quantity "toughness index" that showed a strong correlation with the resultant area retention and stiffness of leather. Toughness index is independent of the geometry of the leather samples. Therefore, even without knowing the thickness or shape of the samples, one can still make an effective comparison of properties.