The different parts of the skin present great differences in terms of thickness, fibrous structure and fiber density. The most homogeneous and valuable part is the butt. The skirts have a much looser and more irregular fibrous structure and a rather uneven thickness.

You can download Chapter 01: Skin Structure in PDF format and in this way you can access the content without being connected to the internet.

In living animals, the skin is protected from the action of bacteria externally by the horny layers of the epidermis and internally by defense systems brought into action by overcoming the resistance of the outer layers. After the death of the animal, the internal defense means cease to act, leaving the skin subject to the action of microorganisms and the activity of enzymes of the tissue that constitutes the skin.

The soak has another important task. During this work process, the hair should already be loosened to a certain extent so that it can be removed more easily together with the hair roots during the haircut.

You can download Chapter 03: The Soak in PDF format and in this way you can access the content without being connected to the internet.

As its name suggests, it removes hair or wool. As it is done with alkaline products, the skin swells. 99% of the unhairing is done with sodium sulfide, in many cases adding sodium sulfhydrate and lime.

You can download “Chapter 04: Unhairing and liming” in PDF format and in this way you can access the content without being connected to the internet.

The fleshing machines are characterized by their cylinder conveyor system, one of which is made of steel, generally provided with grooves, in crossed helices adapted to the skin and against which, when the machine is closed, a rubber cylinder presses that presses the skin against the operating cylinder that is the one with the blades.

You can download “Chapter 05: Fleshing and Splitting” in PDF format and in this way you can access the content without being connected to the internet.

The main objective of this process in the tanning industries is the total or partial elimination, through neutralization, of the alkaline agents that the skins carry from the unhairing and lime. If these were contained in excess in the skin, they would cause a detrimental action in the following processes.

You can download “Chapter 06: Deliming” in PDF format and in this way you can access the content without being connected to the internet.

In the picling operation, the delimed and bating skin is treated with acidic products that incorporate a significant amount of acid into the skin and, at the same time, by lowering the pH to values of around 3.0-3.5, it is possible to totally eliminate the alkali from the skin, even the combined one.

You can download “Chapter 08: Pickle” in PDF format and in this way you can access the content without being connected to the internet.

Once the chrome tanning is finished, it is advisable to place the leather on horse up to avoid the formation of chrome stains and leave it at rest for 24-48 hours to obtain coordination of the chrome salt.

You can download “Chapter 14: The neutralization of chrome leather” in PDF format and in this way you can access the content without being connected to the internet.

In order for us to see an opaque object, its surface needs to send light to our eye. A surface that does not send light, for example a completely black and matte surface, or a non-illuminated substance (due to a foreign source, being hot enough or emitting its own light), would not be seen or, rather, could not be seen. but by contrast with the other objects.