ALL ABOUT LEATHER - WHAT IT IS & HOW IT IS MADE
Readers, let’s talk about leather. At Pala Leather, you know we are all about leather. It is the material that makes so many items that we know and use today. It can be used for purses, couches, shoes, chairs, and our favorite - jackets. Leather is a versatile material that is steeped in history. If you have read our blog before, you have likely read articles about not only the different kinds of leather skins out there but the different quality options as well. But we have not talked about leather itself - what it is and how it is made. So today, we’ll dive a little deeper into the material that we love so much.
A Brief History of Leather
Leather is a durable and flexible material created by tanning animal rawhide and skins. There are a variety of animal rawhide and skins that are used, such as cow, deer, and lamb. The earliest record of leather artifacts dates back to 2200 BCE. Leather is said to be one of man’s useful as well as earliest discoveries. When an animal was hunted, everything was used - the meat for food, bones for tools, and the skin for clothing and protection from the elements. Originally, the skins would not last too long because they would decompose. This led to the experimentation and discovery of preservation, the same way salt was used on food. Leather could also be used for clothing, shrouds, and to make equipment. Beginning with simple drying and curing techniques, the process of vegetable tanning was developed by the Egyptians and Hebrews about 400 BCE. During the Middle Ages, leather became the cover of choice for dining chairs, because it was easy to maintain and did not absorb the odor of food. The spread of industrialization in the 18th and 19th centuries created a demand for new kinds of leathers, such as belting leathers to drive machinery.
Leather is produced in a wide variety of types and styles, and as we mentioned, it is used to make a variety of products. It is produced around the world. There are certain cities and countries that are well known for their leather. The most important leather-producing countries are Italy, South Korea, Russia, Argentina, India, Brazil, the United States, and China. These countries produce the most leather in the world. You may have visited any of these places and walked away with a leather souvenir. Perhaps you went to Italy and purchased a pair of leather gloves in Florence. Or maybe you live in the United States and are a regular purchaser of leather products. Either way, if you have leather, it is likely from one of these countries. It is also good to note if you are visiting any of these places and love leather the way we do to be sure to get something there.
The Science of Leather
Now that we know the basics that there is to know about leather, let’s really talk all about leather and dive a little deeper. Leather is animal hide, but what is the process of tanning the rawhide so that it can be worn? How does it go from rawhide to shoes, jackets, or belts? This is a multi-step and extensive process. You may have heard of the process of tanning leather, or even curing it. But there is a lot that happens in-between. The steps in between curing and tanning are known as beam-house operations.
- Curing -The first step is curing the animal hides and skins. Curing removes water from the hides and skins using a difference in osmotic pressure. The moisture content of hides and skins is greatly reduced, and osmotic pressure increased, to the point that bacteria are unable to grow. This is important because the rawhide will no longer be able to decompose.
- Soaking -After curing, the hides and skins are soaked in clean water to remove the salt that may be left-over from curing and to increase the moisture so that the hide or skin can be treated further. To prevent hide or skin damage by any kind of bacteria during the soaking period, biocides may be used.
- Liming -After soaking, the hides or skins are taken for liming. Liming is a treatment that gets used on the hides and skins. It is made up of milk and lime and it may involve the addition of sharpening agents. Sharpening agents include sodium, sulfide, amines, and cyanide. Liming removes the hair from the rawhide as well as removes natural grease and fats from the hide and skin as well. Liming also allows for the collagen in the hide or skin to be in proper condition for tanning.
- Unhairing and Scudding -After liming, unhairing and scudding occur. Unhairing occurs when hair and wool are removed from the hides or skins. In order to make this happen, unhairing agents are used, such as sodium hydroxide, sodium sulfide, or calcium hydrosulfide. Unhairing does not remove all of the hair, and whatever left is removed during scudding. Scudding is the mechanical removal of the remaining hair. A machine is used at first, and then the rawhide is scudded by hand with the use of a dull knife.
- Deliming and Bating -Once the hair is removed, the pH of the rawhide is brought down to the lowest level that the enzymes that are going to be used may act on it. Depending on the end-use of the leather, hides and skins may be treated with enzymes to soften them so they are pliable enough to work on. This is referred to, respectively, as deliming and bating.
- Pickling -After deliming and bating, the hide and skin get pickled. Pickling a hide or skin is somewhat similar to pickling vegetables in its usage of salt. The hide and skin get treated with salt and then sulfuric acid. Common salt or sodium chloride penetrates the hides or skins twice as fast as the acid and checks the ill effect of the sudden drop of pH.
Curing and beam-house operations may seem like quite the process, but we are only halfway there. After this, the rawhide is now prepped so that leather can be made. The making of leather, or the tanning, is a multi-step process as well.
- Degreasing -Degreasing is exactly what it sounds like: the process of removing excess grease before tanning. In order to do this, solvents or water-based systems are used on the hides or skins.
- Tanning - Tanning converts the protein of the rawhide or skin into a stable material. Turning it into a stable means two things: the skin will not decompose or putrify and it is ready and suitable to use for various purposes. Scientifically speaking, tanning materials form crosslinks in the collagen structure and stabilize it against the effects of acids, alkalis, heat, water, and the action of micro-organisms. It permanently alters the protein structure of the hide or skin, making it durable. There are a few types of tanning materials that you can choose from:
- Mineral tannages - This process uses chromium sulfate and produces a stretchable leather. The leather is sufficiently soaked and the process takes about 24 hours.
- Aldehyde and oil tannages - Tanning with aldehydes and oils produce very soft leathers and this system can be used to produce dry cleanable and washable fashion leathers.
- Vegetable tannages - This makes use of tannin extract which occurs naturally in a variety of different tree barks. Various plant extracts produce brown-colored leathers that tend to be thick and firm. This process takes 3-4 days and it is used to produce stout flexile leather which can be used for belts, soles, shoe linings, and bags.
- Splitting -Splitting occurs when the leather goes through a splitting machine, slicing it into two layers.
- Shaving -A uniform thickness is achieved by shaving the leather on the non-grain side using a machine with blades mounted on a rotating cylinder. Residual chemicals are then removed so that it is ready for dyeing.
- Dyeing -Dyeing the leather is important for the fashion aspects of the leather. There are a variety of color options available as you know from getting jackets - such as black, brown, and red. The leather is either surface dyed or completely penetrated with the dye.
- Finish -Once the leather is dyed and oiled, buffed, and polished, it can be finished with a coat of acrylic or polyurethane to make patent or embossed leather.
Type and Quality of Leather - Where Leather Comes From and Its Grades
Now that you know about the brief history of leather and the many steps involved in making it, let’s go into more detail about the types of leather that exist.
The type of leather is one of the most important factors when it comes to your jacket. It determines the feel of your leather and what your jacket is overall going to look like. The most common types of leather are cow leather and lambskin, but here’s a running list of what you might find (and we are not including faux leather here, but that is always a plastic option):
There are a few leather qualities that are available when you purchase a leather jacket:
- Top grain
The quality of leather refers to the leather itself, and how altered or close it is to its natural setting. It has an effect on how the leather feels as well. Full-grain is the highest quality of leather for any leather product, followed by top grain, genuine, and then corrected leather.
Top grain leather refers to leather that is split from the bottom layers of the leather. Top grain leather is achieved by utilizing the process of sanding away the natural grain from the top surface of the leather. Imitation grain gets stamped into the leather to give a more uniform look. This results in no genuine grain remaining. This results in a leather jacket that is thinner in material and weight. Since leather is heavy and that can be uncomfortable for some people, many times top grain leather is preferred for that reason – it leads to more comfortable jackets. The bottom later of the leather is used to make suede, while the top layer is used for the jacket. Top grain leather is the most common type of leather in high-end leather products, but it is the second-highest quality, although the name suggests otherwise. The surface gets sanded and a finish coat is added. This results in a colder, plastic feel of the leather with less breathability, even though it is thinner and more comfortable. The coat does not develop a natural patina, and it is more pliable than full-grain leather. It is less expensive and is more stain-resistant, making it the most common type of leather in a leather jacket.