Mike Redwood

Columnist

International Leather Maker

Soccer and rugby routinely name their choice for player of the match. It is harder for a trade show. There are too many possible criteria: too much opportunity for favouritism or self-promotion; too much likelihood of bias.

Despite this, the APLF Awards for products worked well and the tanneries who won awards with the tall, twisted blue trophy always valued the public relations gain among their home communities.

More than anything, left me inspired

Despite the doubts, I am going to break the rules and name a person from last week’s Milan Simac Tanning Tech and Lineapelle. Someone who refused to be dragged down by the difficulties and pessimism of the moment and the rather poor decisions taken when people do get worried about the future; and, more than anything, left me inspired.

My rationale is totally based on being unexpectedly startled. As ever, both shows were full of new leathers, new materials, new machines and new chemistries all worthy of comment. Perhaps part was merely the delight of being recognised by the Founder and President of Italprogetti, Mario Serrini who remembered me from the 1970s during my time working in Santa Croce. He passed me to Lorenzo Boldrini, the project engineer whose lucid and infectious account of the new Injection Drum made the machine and its implications for lower water use fully memorable.

Tuscan tanning cluster

The Tuscan tanning community built around Santa Croce and Ponte a Egola are simultaneously intensely local and remarkably global. They have survived not just because they make wonderful leathers but also partly because they were exceptionally good at engaging with the outside world – perhaps a carryover from the days when Florence was a massive commercial power with Barchetto sull’Arno and the special Navicelli Channel barges passing by Santa Croce on the river.

A tannery does not survive by remaining unchanged. It survives by retaining some core knowledge while continuously incorporating new raw materials, new chemicals, new machinery, new markets, new customers, new management and new technologies. It is a form of continuity not so much based on preserving everything but being open to routinely transform to suit the time. Leather itself is versatile and can well accommodate appropriate change be it in end use, performance or appearance.

The key is to be visionary enough to turn industrial knowledge into the basis for the next generation of the industry. A community like Santa Croce has shown decade after decade that it can retain deep tacit knowledge while becoming technologically sophisticated. Its industrial success has depended upon precisely that accumulation of local knowledge.

To work in such an environment is eternally invigorating and to be excited like a child after 50 years is a very odd sensation. But on meeting my personality of the Milan week Ing Boldrini had me back with that feeling again.

Ing Lorenzo Boldrini is a mechanical engineer with Italprogetti Spa. While I have often met Italprogetti around the world and seen excellent facilities established with their equipment I have never bought any of their machines in my career, nor had I met Ing Boldrini before.

Yet, the connection was immediate. He is the engineer who over the last four years has been developing their injection drum for retanning. Boldrini made their drum unusually easy to understand. He explained the saturated-steam and controlled-injection approach with the vividness of someone who has helped turn an idea into a reality: a feeling I have not had since one of the Volvo designers took me through every detail inside and out of a new model in Munich over a decade ago. The drum uses water differently; in a way that means that little is needed and yet the leather ends up with a tighter grain.

Low float processing, like hot stuffing, is far from new and has already been taken further by some of the amazing new dry drums we have been using for a few years. In these perfumes, oils and surface enhancers could be added which took the dry drum methodology from adapting an old dye drum and adding old car tyres to provide extra weight to a refined precision machine.

Taking the “sponge effect” to a new level  

For the retanning stage, the injection drum takes the “sponge effect” in leather processing to a new level. This refers to the mechanical action where the collagen fibre structure of hides is repeatedly compressed and relaxed during drum rotation. This mechanical pounding forces the hides to compress (squeezing fluids out) and expand (absorbing fluids back in like a sponge), facilitating the deep penetration of retanning liquors, dyes and fatliquoring chemicals. What is inside the drum is only what the leather requires. By comparison, a conventional system with a larger float depends on the mechanical action as the hides or skins drop after being carried up to the top by the shelves. The high dilution, however, limits the amount of uptake meaning that the run time must be longer and the uptake falls off well before the liquor is exhausted.

So, the injection drum, which I understand was first shown in 2024 as a prototype, transforms all this. It operates using only 10-20% of standard water consumption. Because the sponge effect absorbs the concentrated chemistry almost perfectly, it results in extremely low chemical waste, reduced production costs and significantly shorter process cycles.

As we come to expect with Italian leather machinery, the design is simple and beautiful.

The alchemist tanner from Santa Croce

My attention was grabbed not only by a first look at the drum and its workings but at the comment that the machine would produce good leather by transferring a formula directly from a standard drum, but that with only two or three trials the “alchemist tanner from Santa Croce” was able to transform the outcome, adjust and reduce the chemical input and achieve a better outcome.

Last week, I wrote extensively about the balance of alchemy and pure chemistry and that while a tanner from the earliest times, such as the Copper Age of Otzi the Iceman, was both a chemist and a craft practitioner with the skill to adapt advancing science to everyday work producing goods or medicines.

What I was being told was that a Tuscan engineer could create a new machine and know that the tanners would look at it objectively and quickly identify the best way to use it create the finest leathers possible. What a magnificent term for those Tuscan magicians, be they of the vegetable/sole-leather tradition or Santa Croce’s more mixed fashion-leather base.

The Italian economic model for leather demonstrates that craft skills and industrial modernity are not opposites. A society can retain deep tacit knowledge while becoming technologically sophisticated. Indeed, its industrial success may depend upon precisely that accumulation of local knowledge.

So, for me, one trade stand, one machine with the technical detail, visible evidence and evident pleasure of an engineer explaining a machine he believes can change how a tannery is designed brought a week in Milan to life.

I am sorry there is no red carpet, or bottle of champagne, Ing Lorenzo Boldrini was the personality of my week of leather in Milan.

mike@internationalleathermaker.com

You can find Dr Mike Redwood across social media at @michaelredwood.

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