All About Leather
LEATHER IS A COLLECTIVE TERM FOR ALL HIDES AND SKINS, WHICH HAVE BEEN TANNED. THE DIFFERENT LOOK AND FEELOF LEATHER, FROM ONE HIDE TO ANOTHER, IS A RESULT OF THE VARIETY OF WAYS IN WHICH THE HIDE CAN BE TANNED AND THE DIVERGENCE OF RAW, UNTANNED HIDES AVAILABLE.
Hides, like human skin, have individual wrinkles and scars that make each one unique and natural. No two pieces of leather are alike; each has its own natural markings, which make it unique. These natural markings are the hallmarks of the beauty of Leather. When you buy leather, you should be aware of the inconsistencies from hide-to-hide and recognize that this is part of the leather’s appeal and what makes it different from all other materials! Leather is the strongest upholstery material known to man. Nature has created its strong physical nature by weaving an intricate network of leather fibers. Leather will not readily burn or melt, and, unlike fabrics and vinyl, it is extremely difficult to puncture. Because of recent improvements in the tanning process, today’s leathers will remain supple indefinitely. While initially more expensive than fabric upholstery, leather is recognized worldwide to be a better investment over time. Under normal conditions and proper care, you can even expect let her to last a person’s lifetime. Leather can stand up to the rigors of daily life in the home or office with minimal care. Unlike imitation leathers, genuine leather will become neither hot nor sticky in summer nor cold in winter. Upholstery leathers used by reputable furniture manufacturers are permanently preserved in the tanned process and do not need any care and cleaning with saddle soaps, oils, etc. associated with other leather products. There is no other material to match the feel and aroma of good leather. Over the years, leather becomes richer and suppler and acquires a soft patina like a well-worn glove or saddle.
THE MAKING OF LEATHER
Less than 5% of all hides harvested each year are suitable for upholstery. This is due to the size of the unblemished pieces required to make a leather sofa. The balance of the hides is used for clothing, shoes, bookbindings and luggage. The overall size and condition of a hide is a critical factor in determining the ultimate cost and quality of a leather sofa. If the hide is deteriorated or of low quality, there is little that the tanner can do to improve it. Due to the large sizes of leather required making a sofa there is little use for the small pieces left over after cutting the hide. These pieces are called waste and must be calculated into the total cost of materials used in making the item. Leather hide sizes vary and range from 38 to 70 square feet depending on the area of the world they come from. The largest cows are located in the colder regions of North America and Europe where the ranges are larger and the animals are better fed and cared for. Due to their larger size these hides afford the manufacturer a better cutting yield. They also have fewer markings such as brands, barbwire scratches and tick bites, which reduce the overall amount of leather necessary to make a sofa. In Northern Europe the cows are grain fed and taken inside at night thus making them much larger and freer of scars. They are kept in by use of electric fences and wooden corrals. Smaller cows are located in Mexico, South America and Australia.The smallest cows come from the Far East and Africa where conditions are rough and feed is not as plentiful. Just as meat is perishable, so too are large hides. If they are not cleaned and treated quickly, the hides will begin to decompose and lose their leather making properties. Processing basically includes two steps: Curing and Tanning.
A hide is an organic material that will begin to decompose shortly after the animal is slaughtered. Fresh hides are composed of 60 – 70 % water. To prevent deterioration in storage and transit from the packinghouse to the tannery, hides are cured in a salt solution with biocide that controls bacterial growth. The hide will remain preserved until it is scheduled to be tanned. Tanneries buy leather hides by the pound from slaughterhouses. They receive the hides while the hair is still on them, in a state we call salted hides. Untreated hides rot if kept damp and dry ones harden. Salted hides are packed in containers and shipped all over the world.
Tanning preserves the hide and makes its natural characteristics permanent. Chromium tanning is a relatively new process developed at the turn of the century. This is the reason why current day leather is softer and properly tanned leather does not crack, fade or peel. There are essentially five steps in the tanning process: Liming A tannery does not know what kind of hide they have purchased until the hair has been removed. The process of removing the hair is called liming. Liming is accomplished by placing the hides in large narrow drums, shaped like a wheel. The drums rotate for many hours until all of the hair is removed. Selection and Sorting The hides are then sorted as to their quality. The highest quality hides are those with the fewest markings. The least amount of work must be done to these hides to prepare them for finishing. Tanning This process preserves the hide and makes its natural characteristics permanent. Tanning is accomplished by placing the hides into large rotating drums for 24 hours. These drums contain alkaline chrome salts. The hides emerge with a slight bluish tone. This state is called the “Wet Blue” state. This process enables current day leather to be softer and not to crack or peel. Splitting The average thickness of a cowhide is 5mm. Upholstery leather requires a minimum thickness of .9-1.1mm. The hides are split in a splitting machine. This operation divides the hide in at least two hides: the grained hides and one or two splits. The strength of the fibers will vary with these hides. The fibers are very strong on the grained hide, and get weaker the deeper the split. The split has much less resistance and flexibility than the grained hide. These splits are processed as suede or embossed with graining to make it look like the grained hide. This is done to offer a lower price on some leather furniture. Aniline Color At the beginning of the finishing process, hides are placed into the wheel shaped drums to soften, remove excess water and apply an aniline dye. This means that they are dyed with a color all the way through. The aniline dye penetrates completely through the entire hide. At this stage the hides are “pure top grain aniline”. These superior hides (free from flaws) are then tumbled in drums for several hours to give added softness. This is called milling. These hides are now done. All other hides progress through additional surface treatments.
BUFFING Heavily scarred hides must receive correction. Feeding them through a machine that is calibrated to the pressure needed to smooth out the hide does this correction. The graining is, therefore, lost in the process. These hides must later be embossed with “graining”. BASE COAT (COLOR) Hides then go through the process of receiving a consistent color over the entire surface of the hide. This color is close to the aniline color already received. This enables a less apparent color contrast, if the hide somehow gets ripped. At this point, the hide is considered semi-aniline, aniline dyed with a base coat of color. These leather are uniform in color with the natural markings being covered. TOP COAT (CLEAR) These hides then go through a clear coat finish. This seals the base color to the hide. The color will now not rub off or be damaged. EMBOSSING Because these hides were buffed smooth, the next process is embossing a grain into it. This is accomplished through heat and pressure. A hot plate is used which has the grain pattern etched into it. Less quality hides receive more buffing and embossing. With more embossing, the hide becomes firmer and less soft to the touch.
UNDERSTANDING THE MARKS OF QUALITY LEATHER
Markings are natural, and in no way affect the strength or wearability of the leather. In fact, these markings are indeed the unique characteristics of the leather. There are Seven Marks of Leather: Graining Graining, like human fingerprints, is unique to each individual hide, and is the hallmark of quality full-grain leather hides. Branding Marks Although seldom found on finished furniture, the branding mark is a part of virtually every hide. Neck Wrinkles So that the steer will have the flexibility needed to move its head while grazing, the skin located on its neck is full and loose. As the neck stretches and contracts, wrinkles naturally occur in the hide. (Not unlike many of us.) Scratches These healed scratch marks are evidence of this cow’s unsheltered life. The fewer marks of this kind on the hide, the more expensive it is. Urine Burns Cows have never won any awards in hygiene, so it should come as no surprise that these acidic urine burns are found on the leg areas of full hides. The affected area actually never has the chance to dry out during the cow’s lifetime. Backbone These natural furrows appear along the backbone of all hides. Again, due to the animal’s physiology, they are your proof of a natural full-grain hide. Stretch Marks Stretch marks appear in cowhide for the same reasons they do in humans. The process of calving requires the stretching of the skin to accommodate the new calf. Nothing could be more natural.