Understanding leather tanning

August 2017

The specially designed experimental set-up for measuring the tanning process in real time using the Australian Synchrotron’s X-ray beamline and detector. Photo: LASRA.

Our knowledge of leather tanning is currently flawed according to LASRA scientist Dr Sujay Prabakar. Dr Prabakar has been researching the tanning process in leather. In a first-of-its-kind in-situ experiment, Dr Prabakar used the Australian Synchrotron to measure the effect of tanning on the structure of leather in real time to improve our understanding of how chrome and other tanning agents interact with the leather’s collagen network during processing.

Chrome was compared with two alternative tanning reagents and all three were shown to have very different reaction routes. Utilising a specially developed sample holder/stirring bar, designed by Dr Bridget Ingham of Callaghan Innovation, and a robotic arm, programmed by Dr Nigel Kirby, Principal Scientist on the SAXS/WAXS beamline, differences in structure were measured for a number of process modifications for each tanning agent.

Individual samples were attached to the specially designed holder and connected to the robotic arm, which stirred the sample and periodically removed it from the tanning solution to conduct the measurements. In this way it was possible to follow the structural changes through the entire leather making process.

This research showed that only around half of the chrome tanning reagent used in a conventional process was involved in cross-linking to collagen. However, increasing the offer of chrome did increase hydrothermal stability from 90oC to 121oC.

Dr Prabakar says this fascinating insight into previously well-defined processing operations shows our knowledge of tanning is currently flawed and further experiments are currently being planned to explain more about the interactions between the main tanning agents used in leather making and skins and hides.

In addition to improving our understanding of the tanning process, the main purpose of this work is to develop optimised tanning recipes to maximise uptake to improve process efficiency and reduce the offer of tanning agent. In the case of chrome, this could be by as much as 45% of the current offer.

Dr Prabaker presented the results at the FILK Leather Days symposium in Oisterwijk, Holland in June. The research is part of the MBIE-funded Project LSRX1301.