What goes on in a tannery?

We all know that a tannery is the place where skins are processed and turned into a material ready for manufacturing.
Yet, what does exactly happen in a tannery? What are the technologies involved in the many processing stages?
Here is a brief overview to better understand the complex world of the art of tanning. Enjoy your reading!

First of all, not everybody knows that tannery materials come from the skins of animals bound for the slaughterhouse, making them a by-product of the food industry. In a way the production cycle of leather is one of the oldest examples of rescue and valorisation of a by-product.
Tanning may be considered a real art, transforming a putrescible skin into an incorruptible and durable finished product.
The complexity of the transformation of skins can be synthesized into a number of steps involving chemical, physical and mechanical treatments which turn the raw material into a finished one. Do you want to know more? Read on.

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1. Green skin

It all starts from green skins, that after removal undergo the initial preservation treatments.

The skin is dried (if small and thin) or treated with sea salt (for larger specimens). In this way we obtain raw skins that may show many pre-exising defects, such as damage by parasites or horn rakes, brand marks, or flaying defects, i.e. cuts or holes.

2. Raw skins

Raw skins first go through the so called beam house operations, that precede tanning and prepare the skins to receive the tanning substances. Through the use of special machinery, the skins undego desalting operations and an initial trimming (to shape the skins).

The next steps are:

  • Soaking
  • Liming
  • Unhairing
  • Fleshing
  • Deliming
  • Bating
  • Degreasing
  • Pickling

 

3. Pickled

The result is a semi-finished product that takes its name from the last of the steps here described: pickling.
The process continues with the following phases:

  • Tanning
  • Samming
  • Splitting
  • Shaving

 

4. Wet-blue

At this point we’ve got an intermediate product, already marketable, which is no longer putrescible and that is called wet-blue, because of its bluish colour. It is from this point that Conceria Stefania enters the transformation process. Let’s take a closer look at each production step.

  • Re-tanning
  • Dyeing
  • Stuffing
  • Setting outand drying

 

5. Crust

We have thus obtained a product called crust, which has already many important physical properties like water repellency, gas permeability, heat and abrasion resistance, etc; we only need to improve its appearance, in order to give leather the required characteristics like colour, shine, suppleness and strength by means of finishing processes.

In short:

  • Staking, milling and buffing
  • Coating
  • Spraying
  • Ironing
  • Glazing

 

6 Finished product

The last and most important phases are those of selection and measuring that are aimed to classify the leathers according to the perfection of the product: these tasks are performed by hand by our expert operators, who evaluate the leathers and classify them according to their quality and intended usage.

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