Tuesday, April 19, 2005

Quality of leather

There's a fair bit of information on leather and leather quality available online, and quite a few Barcelona chair sellers have some sort of 'leather quality backgrounder' available. I was looking for a more independent source of information on this subject, and I found Atalante, Inc.'s Terry Scheller's essay very informative. Here's an exert:

Preface/background
30 years ago I performed a cost analysis for a leather tannery. During most of my career I have purchased and sold leather and leather goods as well as making leather goods. During this time I have talked with hundreds of people that process leather. Over this time period I have learned about leather from the following companies which I purchased (usually just the assets): Manon Handbags, Lorraine Handbags, New England Leather Accessories and Leather World Manufacturing.

Leather knowledge is not rocket science, but still, there's a lot of misinformation about leather. I'd like to try to explain to the general public as well as to others in the industry what some of the definitions really mean, as well as what they now mean in common use.

Composition of leather
Real leather is composed of many microscopic fibers which are inter-linked. When leather is used, it bends and the fibers bend and rub against each other. When it was alive and connected to the oil ducts of the animal, the fibers were all naturally lubricated. During tanning, the oils are first extracted, then later replaced with other oils (usually called "fat liquors.") Once the leather has been tanned, these oils will eventually dissipate (faster in hot weather and exposed to the sun). At this point oils must be reapplied to the leather or the fibers will start cutting into each other as the leather bends and flexes; cut fibers result in cracks in the leather. Once leather develops cracks, the cracks cannot be repaired, although further cracking can be prevented by applying oil or conditioners to the leather. Silicone waterproofing is only a surface coat and will not properly lubricate the leather fibers. Silicone can prevent oils from entering and lubricating leather so is only a quick fix for water-proofing. I personally prefer a natural oil although it will darken most leathers. A general purpose leather lotion or even hand lotion will replenish fiber lubrication and some will not darken the leather except temporarily.

Napa leather
Originally, only sheepskin was referred to as "napa." However, in recent years, the word "napa" has become an adjective meaning "soft," as in "napa cowhide;" this is really a misnomer. If it looks good and feels good, it is probably, but not always a better, more expensive grade of leather. The touch of the leather is called the "hand" of the leather, and the way the fingers slide across the surface is called "drag." My preference is that the ideal soft leather hand be similar to the feel of a baby's skin. A napa leather, or sheep/lambskin, is naturally one of the softest leathers and is closest in "hand" to a baby's skin.; a great tanning technician can approach this "hand" with lambskin.

Full grain leather
The best leather is full grain leather. The reason it is best is because it is usually the strongest part of the leather. At the top of the skin, or epidermis level, fibers are tighter together and hence stronger. In order to be considered "full grain leather" the leather cannot have been buffed or sanded on the top. Therefore, at the surface the leather fibers are most closely inter linked, and hence strongest. When any of these fibers are buffed (sanded) in order to reduce the number of apparent blemishes, leather's natural strength diminishes. Atalante® uses full grain leather for making most of its leather goods.

Only the best (least damaged) skins can be used for making full grain leather. The more natural the dye and top coatings, the more transparent they are. These transparent dyes are usually aniline. Only a small percentage of skins can be used to produce an aniline dyed full grain leather. Cowhide originating as a by-product from USA and Western European beef provides most of the top quality full grain cowhide. This is because cows in most other countries are not as protected by pesticides and enclosures. Brazil, for example, has large herds of cattle, but their hides are marked with thorns, horns, insects, etc. so that almost none of their hides are used to produce full grain leather. Full grain leather may be hot plated or not, the plating (done with a large metal plate which has usually been etched to look like a perfect full grain leather) being added to hide some of the natural defects in leather.

Top grain leather
Top grain leather is full grain leather that has usually been buffed and has originated from the top of the skin. I know it's confusing to many people so will explain further. Both top grain and full grain leather are considered "top grain" because they originate from the top or outside layer of the skin. However, not all top grain leather is full grain leather. Most top grain leather will be buffed then hot stamped with an enormous metal plate. Many times a finely finished top grain can be quite nice, with a variety of textures and finishes, but a cheap and poorly executed top grain on an inferior quality skin can look worse than plastic. Metal plates can simulate large grain cow or fine grain calf as well as ostrich, alligator, basket weave, or flowers. The finest leathers do not need to be plated, but are rare in a world of bugs, barbs, bumps, bruises and brands.

Leather can still qualify as "top grain" or "genuine leather" even though it has been buffed. The buffing process involves sanding off the surface blemishes. The mildest form of buffing leather is called "snuffing," (as in, "Has the leather been snuffed?) Taken to the extreme, the sanding can remove almost all of the natural hair cells of a cheaper leather such as pig (where the pores are unusually pronounced), hence, in this process the leather is weakened because most of the tightest leather fibers are removed. These cheaper grades of top grain leather are usually sprayed with a pigment die (see color).

The cheapest grades of "genuine leather" usually use the cheapest hides (such as pigskin) to replicate cowhide (it can still legally be called "genuine leather.") The best tanneries produce excellent top grain leathers because they only lightly snuff the leather and use top quality finishes and processes to duplicate the look of full grain leather. Often a smooth metal plate or hair cell metal plate is applied with heat and pressure to "kiss plate" the leather, or iron out wrinkles and some irregularities and provide a higher yield of cutting. Sometimes plating is done on a high quality calfskin to replicate reptile skins. The Italian tanneries produce fine cowhide leather replicas of alligator because they use high quality etched plates and spend a lot of time and care applying multiple layers of dyes.

Nu-buc and top grain suede
Nu-buc and top grain suede are top grain leathers with the grain raised to a velvety feel at the best. These types of suede are stronger, have a finer nap, and are more expensive than split suedes.

Split leather and split suede
Split leather and split suede are weaker than top grain leather, and is usually, but not always, less expensive. It is the layer of the leather which is closer to the meat. In this layer, the fibers are not as closely linked and are looser than in the top grain. This is why split leather is weaker than top grain leather (given the same thickness and animal). However, a very thick split leather can be stronger than a thin top grain leather. Cowboys still often use heavy suede chaps for protection. Atalante® makes several tote bags of heavy suede which have long lifetimes, even when used as a tool bags. According to some seldom enforced federal laws, split leather must be labeled as such. Sometimes the split may be stronger, more attractive, more expensive, and hence better than a cheap top grain pigskin that has had enough of its epidermis removed to get down to the "split" in a different way. If the method of doing it is via buffing, it supposedly still qualifies as "top grain" or "genuine leather."

Finished split leather
Finished split leather is split suede with a spray coating of color pigment, bonding agents, etc. which has been plated with a hair cell hot stamp. It is usually, but not always, weaker than top grain leather. When a urethane coating or PU (polyurethane) film is laminated to leather, usually it is laminated to split leather, but once it has been laminated it becomes impossible to tell whether it was laminated to a top grain or a split. Urethane coatings are usually very tough and in many cases stronger than top grain leathers, but the range of qualities in the coatings also varies with the price. Depending on the substrata and the coating it can be stronger than some top grain leathers, and sometimes more attractive and more expensive than a poor top grain leather.

Bonded leather
Many companies brand items that are not legally "top grain leather" or "genuine leather" as "leather" or "genuine goat grain". The problem is that they don't say goat grain "what". Bonded leather is composed of ground leather so that it is reduced to short fibers. They are then mixed with glue and pressed into sheets, then colored with the same coatings used on leathers. If you are looking at a stiff leather, looks can be deceiving. Bonded leather is only as strong as its thickness, the material to which it may be laminated, and the possible addition of a top urethane coat. Poor bonded leathers are weak and will not last long with use. The best bonded leathers will last longer, but not as long as genuine leather.

Types of leather (animal)
Leather is primarily a by-product from an animal used for food. Mink is one of the few animals which is raised primarily for its skin or pelt. Cowhide is probably the most popular, and is relatively strong. For its strength and also because of its "breathability", it is still the best material for shoes and many personal accessories. Crocodile, lizard, water buffalo, and goat are other durable skins. Sheep skin and especially lambskin, are relatively weak and will not last as long as the other leathers just mentioned, however, they are especially soft.

Color
The coatings applied to leather vary in strength and appearance The more transparent the dye and more natural looking the skin, the higher the price and quality. Aniline dyes are considered the best; they are transparent dyes which are usually added in a drum and preserve the transparency. Thicker pigment (more opaque) colors are sprayed on, not only for color, but also to hide blemishes and imperfections in the skin. Sometimes many different combination pigment layers contribute to a "semi aniline" look that has a bit of depth

Design considerations
On the other hand, in order to craft many items for maximum durability I would choose a thicker leather (which never feels as soft as a similar thinner leather). Good leather goods designs are done with the thought of the type of leather to be used in mind. Also, certain types of designs perform best with certain characteristics of leather. For example, if I wanted a briefcase to stand up, I would usually choose a thicker leather with more "stand up." Fortunately, this leather description is similar. A leather with more "stand up" is stiffer and not so floppy as soft leather.

Cost
Cost varies according to the scarcity and demand for a particular type of animal skin as well as in the cleanliness of the skin, and the art and types of finishes applied. A clean and elegantly tanned and finished calfskin costs three times as much as a cowhide from an older animal whose skin is full of scratches, bug bites, skin diseases, etc. and must be heavily corrected to cover the natural marks which many people call "imperfections." Ostrich and alligator are among the more expensive types of leather. Rare types of leather are monitored by US Fish and Wildlife to make sure that the skins have originated on special farms or areas not suffering from endangered species regulation. Both of these animals are now raised commercially and their meat is highly prized (and priced.) If a skin is rare and exotic, it is probably illegal to bring it into the United States. Yes, if you try to bring a leather product made from an endangered species into the country, it may be confiscated.

Recommendations
When looking for quality, look to a reputable manufacturer who makes high quality products and provides customer satisfaction.


1 comment:

b5 said...

Hi Mosez, Out surfing for information on skin treatment & happened upon your site. While Quality of leather wasn't exactly spot on, it did strike a note with me. Thank you for the really good read.