Wet Blue & Wet White Leather
Pre-Tanned Skins
What is the so-called Wet-blue or Wet-white leather?
Wet blue (or wet white) leather derives from the pre-tanning phase, which is divided into two main types: chrome tanning and vegetable tanning. Before explaining the difference between the two types, it is necessary to describe the main steps that lead us to obtain pre-tanned leather hides.
The preliminary stages to tanning of leather
The tanning phase of the hides is preceded by some operations, which are defined as “preliminary tanning operations”. These operations consist of descaling, maceration and degreasing. The descaling operation, performed to complement the depilation, has the purpose of removing lime residues from the hides and bringing them to the optimal conditions for the next stage: maceration. Maceration, on the other hand, aims to “purge” the skin of all keratin residues, interfibrillar matter and fatty substances not yet removed.
The next phase of the tanning production cycle is degreasing. In this case the skins are subjected to this procedure only if they contain an excess of fatty substances; for this reason it is usually performed on sheep and pig skins. The last phase before tanning is called pickling, which is carried out to reduce the pH of the skin in tripe before subjecting it to actual tanning and the choice of its parameters depends on the next tanning phase. This phase is most often performed in the pickel liqueur, from which it takes its name.
The tanning
Now the leather is ready for the tanning process: the purpose of this process is the penetration and fixation of the tanning material in order to obtain stabilization of the dermal tissue and avoid decomposition. In addition, tanned hides increase their size, resistance to mechanical actions, chemical agents and heat. From this first tanning process (also called pre-tanning) we obtain two types of intermediate products depending on the chemical reagents that are used: Wet Blue leather and Wet White leather.
The different types of tanning
Vegetable Tanning
Vegetable Tanning is performed with vegetable or synthetic tannins. Tannery materials and substances, which in the past were used to transform raw leather in finished skins, were mainly of vegetable origin. The active ingredient responsible for the tanning process is in this case the tannin, a substance that is, more or less concentrated, in some parts of certain plants: in the rind, in the leaves, in the wood or in the fruit. The intermediate product resulting from this process is the pre-tanned material called “Wet White Leather“.
Chrome Tanning
In recent times, chrome tanning has made shorter and even simpler the chemical and technological operations, with significant saving of vegetable tanning products. In addition, chromium salts are able to create a bond with the skin, which is certainly more stable than any known tanning process to date. Tanning takes place in a single bath, where the tanning fluid is made up of chromium sulphate solution, partially based on the addition of a certain amount of soda or other alkalinizing products. This operation is carried out in a drum and must be preceded by the pickling, which serves to facilitate and adjust the penetration of chrome into the skin. At the end of tanning, the skins have a light blue color (hence the name “Wet Blue Leather“) and they have a remarkable acidic reaction, which must be partially neutralized by deacidification before proceeding with dyeing and fattening.
The drums role in the tanning process
These two tanning techniques just described are the most used. It should also be noted that the tanning process takes place in special containers called drums, which are large cylindrical containers built with wooden slats held together by metal circles; whose dimensions vary according to the type of operation for which they are used. In order to guarantee this product penetration, inside the drums there are rungs, having a rounded tip to avoid damage to the hides, about 25 cm long which allow, during the rotation of the drum, to drag part of the hides upwards, to then let them fall on the others, in order to intensify the mechanical action imposed by the rotation itself.
Mapel today represents one of the major exporters of cheap Wet Blue and Wet White leather
In the wet-blue and wet-white field we are specialized in inexpensive types of leather and in particular splits, bellies, shoulders and butts. In our warehouses you will be able to see a wide selection of leather hides stored in this intermediate stage and ready to be re-tanned according to your needs.
Our staff is always available from Monday to Friday during opening hours
Email: info@mapelec.it
Tel. (+39) 0571 499345