What Is Leather Manufacturing and How Does It Work

The process of creating leather is complex and complicated. Accuracy and care must be taken to ensure that the procedure produces high-quality leather with the same finish every time. Beginning with the raw material, the process will result in a piece of leather that is prepared to be made into a bag, article of clothing, or other leather product. Three essential steps make up the modern commercial leather-making process: preparation for tanning, tanning, and processing tanned leather. Typically, the complete procedure takes 6 to 8 weeks.

Raw material

Since a good hide yields between 80 and 90 percent, the quality of the hide produced will depend on the quality of source. For instance, cows maintained close to barbed wire fences, exposed to a lot of insect bites, or those who have had electric cattle prods placed on them may suffer damage to their hide. In order to prevent flaws and holes, the hide yield in this case is more likely to be in the range of 60%. Even some diets containing cereals or growth hormones may result in a poorer quality hide.

The surface must first be properly removed before the flesh can be removed, either manually or with the aid of a fleshing machine. If the process is carried out manually. It is crucial to do it as soon as possible because the material dries out fast. The technique should leave a crisp, white surface behind. The hide is now safeguarded during storage and delivery before it reaches the tannery.

Preservation

A dehydration procedure is followed by air drying, wet or dry salting, or pickling with acids and salts before a hide is delivered to a tannery in order to prevent it from starting to degrade. If the hide is not salted or frozen within a few hours of being removed, it can become unusable and wasteful. Until the next step is ready, this hide will stay salted.

Soaking

These salted hides are now immersed in water for a few hours to several days to wash away all water-soluble impurities like dirt and salt and return them to their former softness and shape. The water lost during the salting process or during transportation can be reabsorbed using this method.

Liming

The hair on the hide must be removed, therefore it is first loosened by the liming procedure. It involves soaking the hair for one or two days in a chemical solution containing calcium oxide or a solution of lime and water. During this procedure, the hide will also soften and swell to a thickness of around 4 mm, at which point it can be divided into two layers.

Fleshing

Here, superfluous flesh is removed from the hide by running it through a machine. At this point, hides may be divided into layers so they can be used for various leather products. Due to its tighter fiber structure, the upper portion of the skin is used to produce leather goods of the finest quality, such as full grain leather. And because it is of lower quality than the top layer, the bottom layer is utilized for leather that costs less. The majority of the time, top grain and split leathers like these are used to make shoes and handbags.

Deliming

The main goal of deliming is to progressively neutralize the alkali in the pelt while avoiding abrupt pH changes that could cause tissue distortion or disturbance.

Bating

The elimination of any leftover lime, scud, and other materials broken down during liming can be considerably improved by a lengthy deliming. This procedure is finished by bating, which relies on the employment of enzymes, leaving the pelt flat, relaxed, clean, and prepared for pickling and tanning.

Pickling

The pelt is brought to the weakly acid state necessary for most tanning methods using weak acid and salt solutions. Pelts are preserved using stronger pickling solution. So they can be kept or transported in a stable state for several months at a time.

Degreasing

Before tanning, the hide can be cleaned of superfluous grease such as natural fats and oils using solvents or water-based processes.

Tanning

Through the preservation of the hide and the halting of degradation, the tanning process transforms the protein of the hides into a stable material. The hard, unyielding material is transformed into a supple form throughout the tanning process. The type of process depends on how the leather will be used in the end. There are various sorts of tanning methods and materials. The most popular tanning substance is chromium, which gives tanned leather a pale blue hue (a result of the chromium). This product is sometimes referred to as “wet blue.”

The hides must be placed in a particular tanning drum along with a unique tanning solution. This drum will contain a unique mixture of either vegetable tanning chemicals or a chromium salt mixture. The oldest tanning techniques are for plants. The majority of the time, a vegetable tanning mix comprises tannin extracts. They are naturally present in tree bark, roots, leaves, and seed husks. This results in leather that is flexible and typically used for furniture or luggage. The different vegetable tanning processes can take several weeks or even months to finish.

Re-tanning

The leather can then be fully prepared for its intended use by going through the re-tanning process in the following stage. The goal of this process is to give the leather the desired “character”. You can alter the leather’s appearance, texture, fullness, weight, and color during re-tanning to add features that distinguish a given bag, jacket, car seat, or other finished product in the marketplace. The process will be repeated, this time removing the extra moisture under pressure while utilizing either the vegetable mixture or the chromium salts (or a combination of both).

The hides need to be dried after the tanning procedure is finished. This drying can take place using a variety of techniques, including vacuum drying or air drying. A hide is air dried by being placed on a rotating surface, such as an overhead conveyor, and allowed to dry completely. The fastest way to dry something is by vacuuming up all the air surrounding the hide. The hide will somewhat contract as a result of this technique, but it will retain its tight and smooth texture.

An ideal foundation for the leather dying stage can be created by using a bleaching chemical during the re-tanning step. Rp Comtrade makes sure that every product should go through this process.

Dyeing

The technique of dyeing leather into a wide range of colors is crucial in addressing fashion demands. This can range from bright, dramatic colors to the dark, leather-like browns and blacks. Drum dyeing, spraying, brush dyeing, and staining are typical dyeing techniques. The leather is subsequently lubricated with a mixture of oils and greases. It also improves its strength, softness, and water-shedding properties.

Drum dying is the most popular method of dyeing. Although it can take a very long time since hides must be added to a big drum with the chosen dye and left there for a long time to ensure the dye takes. A cutting should be made after around 8 hours to make sure the dye has properly permeated the hide. If not, the leather will appear spotty. The leather must then be carefully cleaned to eliminate any remaining color or chemicals. The hide should be completely dry after being cleaned.

After that, the leather is dried to a moisture content of roughly 14 percent. Either by stretching it first and then drying it in the air or a tunnel, or by any combination of these methods. The less popular techniques of paste and vacuum drying are also available. The leather is finished by being reconditioned with damp sawdust until it has a consistent moisture content of 20%. The grain surface is then coated to further increase its resistance to abrasion, cracking, peeling, water, heat, and cold. It is then stretched and softened.

Finishing

The finishing process is the final step in creating leather after the dyeing process is finished. The leather will be worked at this point to give it the shiny luster and supple, flexible character that are so desirable in leather. A finish that might be easier to clean while also protecting the surface. If a naked leather is wanted, this step would be bypassed. The leather is stretched and then heavily lubricated with natural oils using a device known as a staker to soften the material. The leather’s pore structure is additionally tightened by this stretching process. This contributes to the creation of an improved finish that is appealing to customers.