Mike Redwood
Columnist
International Leather Maker
You will struggle to find mention of the term “patina” related to leather in ancient texts. Search through the early leather literature, the trade manuals, the tannery handbooks, the craft guides from the 17th to 19th centuries, nothing explicitly theorises or celebrates patina in leather. It simply was not a category that needed articulating, it was a given just as trees grow rings or wine ages.
The concept only became visible when changes in leather technology started to produce new leathers where no patina developed and consumers started to realise what had made their leather armchair or handbag special for them. This is a fundamental dynamic in material culture history, we tend to document things at the moment of their disappearance or endangerment, not while they are ubiquitous.
Now, talking about the patina is a common thing when marketing leather and tending to be a misnomer since the vast majority of leathers do not exhibit it. It is time it was properly defined, and tanners encouraged to ensure more leathers display it at least in some ways. Since it ties in so closely with longevity and the fight against fast fashion, it is perhaps a proper task for Leather Naturally.
Chrome versus vegetable tanning
One aspect that always stands out is how closely patina is related to vegetable tanned leathers and the belief that it will not occur with chrome leathers. This is an oversimplified binary often drawn in popular leather writing. The reality is that chrome tanning, as an industrial process, only rarely escapes a major retanning process. Pure chromium is economic and fast compared to a vegetable tanning but it creates a dry, empty leather. In certain performance areas, careful fatliquoring sees pure chrome through, so benefit can be made of its high shrinkage temperature and other properties.
Yet the vast majority of chrome tanned leather goes on to receive a retannage, and vegetable tannins (chestnut, quebracho, mimosa, phenolic syntans) are among the most common retans used, precisely because they add body, fullness and a degree of the reactive surface character that pure chrome-tan lacks. A chrome-plus-veg retannage can produce leather with genuine, if more modest, ageing capacity such as the Horween Chromexcel, “the original pull-up leather; using time honoured techniques and formulas that were developed nearly 100 years ago” – is just the earliest and most famous leather that is chrome tanned and retains its patina. In fact, its ability to develop a rich, distinct patina is one of its most famous and desirable traits with the “teacore” effect with their black creating a much-loved vintage look.
The degree of patina on any retanned chrome leather will sit on a spectrum determined by the proportion and penetration of the veg retannage and by how the fatliquoring has been managed, but the capacity is real.
The finishing layer is the culprit
In fact, the decisive variable is probably not in the tanning route but in the finish. A chrome-veg retanned, aniline-dyed leather with minimal surface treatment will age perceptibly and develop character. The same leather corrected, buffed, sealed with a heavily plasticised pigment coat and then embossed or top-coated effectively becomes inert, the finish forms a physical barrier between the leather substrate and the environment. Oils, UV light and handling can no longer reach the fibres. Patina is impossible not because of the tanning chemistry but because the surface is sealed.
The clearest evidence for this is the behaviour of pull-up leathers, heavily wax-and-oil-dressed leathers in which the finish is itself the absorbed oils rather than a surface film. These patinate dramatically regardless of tanning route because the “finish” remains open and interactive. Conversely, a fully veg-tanned leather with a heavy pigmented spray coat will not patinate meaningfully either. Indeed, for my 70th birthday I was given an expensive document case in English Saddle Leather from a UK tannery I was associated with at the time. As is frequently the case it had been buffed and heavily finished. When I took it on a visit to my local friendly oak bark tannery the owner scoffed and told me in his area this leather was nicknamed a “painted lady.” It is smart and elegant and will certainly last decades; but I do accept there is no chance of patina style development.
Accelerating plasticisation
What is more of a concern is that in recent years demand from brands to present what they describe as perfect products and worries about increasing defects on raw material as a result if husbandry and climate change has meant that more and more leather gets pigmented. When I got involved in fashion and sports glove leathers in the 1980s all of our huge production was full aniline with a polishing with a rotating plush roller the only “finishing” the leather received. No sprays, coatings or plating. Today such leather is a rare find from a few French or Italian producers and recently the CEO of large glove organisation told me that aniline dress glove leather was near impossible to buy.
So let us be clear that while the tanning route creates potential, the finish determines whether that potential is realised or suppressed. The heavy pigment coat kills patina at source, regardless of what lies beneath it. The commercial logic of such finishes, hiding surface defects on lower-grade hides, ensuring colour consistency at retail, and reducing care requirements for consumers, is precisely what drove their adoption, and their adoption is what made the absence of patina widespread enough to be noticed and mourned.
If any sector of the leather industry needs a rethink, this is it.
mike@internationalleathermaker.com
You can find Dr Mike Redwood across social media at @michaelredwood.
Publication and Copyright of “Redwood Column” remains with the publishers of International Leather Maker. The articles cannot be reproduced in any way without the express permission of the publisher. The views are those of the author and not necessarily those of ILM.
