Wet white tanning
Innovation in chrome-free leather
All tanners are facing the same problems of minimizing the environmental and health impact of their processes when selling into the global market.
Regulatory pressures oblige tanners to make continuous improvements in the processing operations. The regulatory authorities and consumers are looking more closely at whether hazardous substances, such as certain preservatives, some azo-dyes, and chromium (VI) are present in leather and leather products.
Closer monitoring of this aspect has revealed that leather and leather products sometimes contain some hazardous substances like chromium (VI) although only chromium compounds in the form of chromium (III) were used in the tanning process. It has been concluded that the chromium (VI) in the leather is formed by an oxidation of the chromium (III) added to the leather during the tanning or the retanning processes.
In order to avoid this issue, wet white leathers are produced by combinations of synthetic tannins, vegetable tannins, glutaraldehydes and minerals, such as aluminum and zirconium.
Wet white tanning allows making chromium-free leathers with the same equipment that a chrome tannery uses.
A wide variety of different types of leather can successfully be produced using the wet white system, including automotive leathers, upholstery leather, garment leather and shoe upper leather.
Advantages of wet white tanning
- Wet-white leathers are lighter in color and can be converted into pastel shade leathers
- Shrinking temperatures of at least 70°C
- High softness
- Good lightness
- Natural sensation
- Pleasant touch
- Beauty over the time
- High-performance leather can be obtained, often better than chrome tanning
- Leather can be burnt without the hazard of chromium (VI) formation
Disadvantages of wet white tanning
- Slightly higher production cost compared to chrome tanning. Newer techniques have reduced this difference
- Requires more controls compared to chrome tanning
The driving force behind the push towards chrome-free tanning is the automotive industry, which is the biggest user of chrome-free leather. In 2000 a regulation came into force in the European Union which requires that 95% of abandoned vehicles must be recycled by January 2015 (EU End-of-Life Vehicles Directive N. 2000/53/EC). Leather not containing heavy metals is more easily biodegraded than leather which contains chromium. Wet white leather can be burnt without producing chromium (VI).
Although chrome-free leather only accounts for around 5% of total automotive production, the major automotive leather producers are nearer 30% chrome-free. Taking Audi as an example, all its car interiors leathers are free of chromium.
The persistence of chromium (VI) in leather goods continues to be problematic as highlighted by its continual presence in weekly EU RAPEX reports.
The consumers growing concerns and some legal developments result in an increasing demand for Free of Chrome leathers, with health considerations playing the major role for consumers.