Ever wondered how leather – the beautiful material used to make clothing that makes you look terrific – is made? It may not seem like a lot, but much work goes into converting raw material into the finished usable material used to make leather bags and accessories. People in charge of the whole process are called tanners, and it takes almost two weeks to turn to hide (the raw material) into leather.
Furthermore: experts must inspect the finished material to ensure it meets all quality control specifications. Here are the processes involved in making leather.
Obtaining the Raw Material
The raw materials come from animals, mainly cattle, pigs, and sheep. The quality of the raw material obtained largely depends on the environmental conditions where the animal was bred and the feeding method used. For instance, cattle raised in a moderate climate produce better hides than the ones bred in extreme environmental conditions.
If there was excessive use of growth hormones in the animal's diet, the quality of the hide produced from such an animal is lower, making it more prone to insect attacks that can lead to holes in the hide and thus lower yield for the manufacturers. A yield of 60% or lesser is low, while a yield of 80% is of high quality.
Curing the Raw Material
The curing process involves all the methods used to preserve the raw material before the processing stages. The hide is covered in a large amount of salt or placed in salt brine to prevent the risk of the raw material from decomposing quickly.
An alternative to salting is freezing the hide at an extremely low temperature. This preservation process is done a few hours after the animal hide is collected to improve yield results and reduce decomposition and deterioration.
Hide still has components of animal flesh in it, so during preservation, the sides containing flesh are made to touch through folding.
Cleaning the Hide
As soon as the hide has undergone the curing process, it is taken to the tannery for storage. When it is time for processing, the hide is soaked in water for an extended period- typically hours to days- to remove excess salt in the hide and revert the dehydration process.
Soaking the hide also helps to remove dirt and other unwanted materials. If the hide contains a lot of hair, it is made to undergo the liming process. Liming means using alkali chemicals to remove all unwanted hair in hides. The resulting material is called a pelt.
The pelt still contains fleshy materials that are not needed, so it is made to pass through a machine that gets rid of the flesh. Pelt has limited storage time and is sometimes split into different stages. Since there was an application of alkali, neutralization is done by Deliming through a slow or gradual addition of acid.
This process has to be done as slowly as possible to avoid excess acidification that could make the pelt undesirable for use. Enzymes are then added to the pelt to cause it to straighten and flatten out. If the pelt seems oily or greasy, a solvent or water is used to reduce the greasiness.
Splitting
The pelt that has been highly moisturized is about 4-5mm thick. It is then split into layers- the upper portion or dermis has a highly compact structure, making it ideal for making high-quality leather products. The strength of this topmost layer makes it durable enough to withstand the effects of tanning(to be discussed in the next step).
The bottom layer, however, is known as the split segment and isn't as strong as the topmost layer. This part is used to make bags and shoes since they are not of very high quality and are relatively inexpensive.
Tanning
Tanning is the process of converting the pelt or hides into leather. This involves using chemicals that change the pelt's structure, converting the proteins present in the material into leather. This procedure completely halts the decomposition process.
For the tanning process to occur, the hides are placed into a tanning drum using minerals like chromium salts and vegetable tanning agents for 8-10 hours while the drums are rotated constantly. The tanning solution is also constantly reheated to allow deeper penetration into the material. Bovine oil is then added to make the leather appear softer but stronger.
Chromium salt is the most popular mineral for tanning, making leather supple. Sometimes, this chemical is used alone or combined with other vegetable tanning agents to make the resulting leather firmer and tougher, which is ideal for making leather bags, belts, and shoes.
The hide has been converted to leather. However, there are still a few more steps to undergo.
Shaving
The shaving process gives the leather desired thickness depending on the kind of product used to make it and the quality.
The shaved parts are not wasted and can be recycled to make other products like bonded leather and belts.
Re-tanning
The resulting leather is re-tanned using vegetable tanning agents, chromium salts, or a combination to impart specialized texture to the leather.
A process called “sammying” is then used to remove almost half of its moisture content through machines.
Stretching and Drying
The leather is stretched out and dried using an oven, vacuum, or air. The drying process allows for the extraction of water content, enabling the leather to have a smooth, refined look and texture. It is then softened to become supple using a stalking machine.
Finishing and Grading
Finishing helps to detect and fix any irregularities in color by dyeing. After the dyeing process, gloss is added to the leather to make it shine and give it a water-proof protective layer.
Quality control tests and final grading help inspect the finished products' quality, check for scratches and other defects, and feel the texture. Quality control helps to ensure that the leather meets all the specifications before shipping to the customer.
The finished product is then horse-draped or rolled with the finished leather inwards to prevent any damage to the product during shipping.
Conclusion
The process of making leather is a long one but rewarding when done right. The finished leather material then gets in the hands of the designer, who turns it into fabulous fashion pieces like leather bags, shoes, and belts that everybody loves.
