Preparing the materials from hide to the fine-quality leather is a long process requiring time, knowledge, equipment and precision. For those of you fascinated in the leather products this article will hopefully help you imagine what is going on behind the doors of leather manufactories.
Production process of wet-blue leather
Production of the wet-blue leather has its specific flow. First, raw stock is selected – the material is mostly acquired from the cattle hide. Secondly, unnecessary part of the skin is trimmed and prepared for weighting. Measuring the weight is essential since appropriate amount of chemicals needs to be used for fleshing, and it depends solely on the weight of the skin. The next step in wet-blue leather production is the soaking which consists in rehydration of preserved raw hides. You know the soaking is done when flesh side becomes slippery. Then it is time for liminig which involves treatment of soaked hides with milk of lime (CaO). At this state, the hair is removed from the skin to be next fleshed, weighted again and put into a chemical bath.
Next stage is deliming – done to remove the lime, swelling and plumping.
Chemicals used in this process need to have ability to reduce pH. The following stage is called bathing and it is really interesting since here is when we decided the use of the finished leather. Depending on it, we treat the hide with enzymes (weak, mid strong or strong) to soften it appropriately. Next, comes the pickling – we call it a process of treating delimed pelt with a solution of acid and salt. Among other advantages, pickling helps to reduce astringency of chrome tanned leather.
Wet-blue leather is chrome tanned using chrome tanning salts and this process (taking place after the pickling) leaves the hide with blueish color. Then, the skin is going through basification – done to increase the strength properties of the material. After that, the final stage of preparing the leather is draining out the chrome liquor and piling up the material for 4-7 days in order to complete the fixation and polymerization reactions. It’s important to note that chrome-tanned leather is generally stronger than vegetable-tanned leather, so has a wider variety of possible uses.