Cardboard hard (dehydrated) leather’

[togwt]

Microscopic view of Leather`s Corium (Fibres)

Research



Information regarding the care of leather is scarce, often contradictory, misleading, or simply wrong. Misinformation can lead to inadvertent damage to your vehicles leather upholstery; my goal is to present clear, concise, accurate information.



There is a great deal of conflicting information on leather care being put out by leather experts themselves who use baffling pseudo scientific techno speak as another marketing ploy, which makes it difficult to find a definitive, unbiased answer. It had always confounded me that such a simple subject has been made into something so complicated.



After various meetings and discussions with leather tanners, their chemists and fat liquoring formulators and many leather care product manufacturers I’ve gained an understanding of this versatile material on both a practical and scientific level.



I have always thought that the more facts and information you have at hand the easier it is to judge what information you are being given. After all, how can you fully understand and properly use any product unless you have all the facts? In the final analysis; it’s your vehicle, your hard earned money and your choice



Leather Tanning Process



Is the process which converts the protein of the raw hide or skin into a stable material which will not putrefy and is suitable for a wide variety of end applications. The principal difference between raw hides and tanned hides is that raw hides dry out to form a hard inflexible material that when re-wetted (or wetted back) putrefy, while tanned material dries out to a flexible form that does not become putrid when wetted back.



Leather is hygroscopic (naturally absorbs and retains water), meaning it’s also susceptible to losing the moisture necessary to keep it pliant and soft. The denaturing process of leather tanning removes moisture from the hide; water-based products restore the lost moisture of leather hides to maintain its natural flexibility.



Fat liquoring



Leather, at the time of completion of the tannage does not contain sufficient lubricants to prevent it from drying into a hard mass. Almost all light leathers need a greater softness and flexibility than is imparted by tannage. This is attained in the fat liquoring process by introducing oil into the leather, so that the individual fibres are uniformly coated. The percentage of oil on the weight of leather is quite small, from 3-10 %. The precise manner in which this small quantity of oil is distributed throughout the leather materially affects the subsequent finishing operations and the character of the leather.



These fat liquoring formulas are closely held secrets, passed down through generations; this is the origin of the new car ‘leather smell’. This is one reason why one company`s leather can have a totally different feel, fragrance, texture and softness from another company`s product. Modern leather tanning methods; chrome tanning, seals the hides ‘locking in’ the necessary fats and oils



Every leather tanner has his own, unique, blend of tanning oils. These formulas are closely held secrets, passed down through generations; they are neither volatile nor migratory, this is the origin of the new car ‘leather smell’. This is one reason why one company`s leather can have a totally different feel, fragrance, texture and softness from another company`s product



Leather Hides



Leather is the fibrous corium or structural part of animal skins as shown above in microscopic cross-section. For a material that is so versatile, stylish and practical you could be fooled into thinking it is an extremely complicated material...far from it.



There are basically just three main materials from which hides and skins are made: water 60-65%, protein 25-30% oil and fats 5-10%. The protein is mainly collagen (found in many cosmetics) and it is this collagen that is transformed into leather by the tanning process.



Raw hides have four main parts - an epidermis, grain, corium and flesh



Two of these layers, the epidermis (which is a thin protective layer of cells during the life of an animal) and the flesh are removed during tanning by a process called liming.



This leaves just the grain and the corium, the parts that are used for automotive leather upholstery .The grain layer is made of collagen and elastin protein fibres and its structure varies quite a bit depending on the age, breed and lifestyle of the animal. The grain carries many distinctive marks such as insect bites, growth marks and wound scars giving the leather a unique appearance.



The corium is packed with collagen protein fibres, arranged in larger bundles and interwoven to give the structure great strength, excellent elasticity and durability. In the tanning process these fibres and impregnated with collagens and polymers that are designed to hold them together and keep them supple. Much of the suppleness of leather comes from its moisture content. After tanning the skin is protected with a thin pigmented (colour) urethane and then a clear, abrasion resistant topcoat.



Hydration

Definition [: to supply water in order to restore or maintain fluid balance:]

When leather tanner’s talk about conditioning leather they are referring to its moisture content, re-hydration is used to restore or maintain fluid balance (transpiration and evaporation of moisture); not the replenishment or replacement of the fat liquoring, oils and / or waxes.



Moisture balance is a sine qua non (an indispensable and essential action) in leather care. Leather naturally absorbs and retains moisture vapour, meaning it’s also susceptible to losing the moisture necessary to keep it pliant and soft. One of major attribute is its ability for transpiration; allowing the movement of moisture back and forth (evaporation and hydration), which it does even better than wool.



This means not just its permeability to air but its permeability to water vapour, on the other hand, whilst it absorbs water vapour it doesn`t readily absorb liquid, so a light rain will not harm it and a damp cloth can be used to keep it clean, however the introduction of any solvent-based products accelerates aging of the leather.



Water-based products to a certain extent hydrate finished leather, more so on perforated leather. Water molecules are smaller than the micro pores in urethane, so it can permeate the finish in vapour form. This is essential to transpiration (evaporation and hydration) to maintain a moisture balance as well as the suppleness and leathers natural flexibility, keeping finished leather at its optimum physical performance level, along with softness and strength



Ensure that the surface of the finished leather is clean and dust-free. Fill a fine mist atomizer spray bottle (Kwazar Mercury Pro) with distilled water; lightly mist the surface and then using a damp 100% cotton towel wipe the surface



‘Cardboard hard leather’ is certain indication that the leather has been allowed to dehydrate. The corium is packed with collagen protein fibres, arranged in larger bundles and interwoven to give the structure great strength, excellent elasticity and durability. In the tanning process these fibres and impregnated with collagens and polymers that are designed to hold them together and keep them supple. Much of the suppleness of leather comes from its moisture content. After tanning the skin is protected with a thin pigmented (colour) urethane and then a clear topcoat.

Be cognizant that you are dealing with the leathers finish, not the hide itself

When corium fibres lose moisture they shrink, when they are hydrated with water moisture they swell. The best way to care for finished leather and to keep wrinkles to a minimum is to keep the leather properly hydrated and avoid, as much as possible, these shrinking and swelling cycles. Keeping leather hydrated only requires a regular wipe down with a damp cotton towel.



To restore the suppleness to finished leather apply Leather Masterâ„¢ Soft Touch (Vital) to a clean surface - this is not a conditioner per se but is used to improve and maintain the tactile feel and lustre by rehydration and to ensure the leather remains matte, soft and supple.



Schedule



The age and general condition of your leather and its environment will determine how often it should be hydrated. The recommended frequency for hydration is a function of the environment. For example, in an automobile, the head rests and top of the rear seat backrests tend to dry out very quickly due to direct, prolonged sun exposure.



Ideally it should be initially thoroughly cleaned and hydrated so that it`s in as best condition as possible and then simply regularly maintained to keep it in that condition.



A regime of monthly hydration of leather in hot, arid climates and the southern states is de rigueur; Florida, Texas and Arizona, especially during the summer months, would not be out of line. In a northern climate or during winter months the interval between hydrations could be extended 60 to 90 days.



It can be vacuumed and maintained weekly or monthly depending on the usage of the vehicle and owners requirements.



Rain Ingress Damaged Surfaces



There are no leather finishes that are water proof. Leather hides used for automotive upholstery consist of approximately 45 square feet, that are stitched together to form a covering. The thousands of stitch holes allow any standing water to be absorbed and migrate laterally under the urethane finish. The perforated leathers used on many BMW, Mercedes-Benz, Porsches and other cars also allow standing water to permeate the urethane.



Rain ingress by inadvertently leaving a moon roof or vehicles windows open during a rain storm will very likely soak the leather seating and perhaps the carpets. The damage would depend on how long it`s exposed to water. Left for a couple of weeks your whole interior would probably have to be replaced.



Finished leather (urethane pigmentation) is water resistant, which means if you spill or allow liquid onto the surface and clean it right away it should not cause problems. Damage to the electronics that are under the seats (seatbelt sensor, seat positioning motor, air bag sensors, and etc) may be a cause for concern



Obviously the amount of damage could be lessened dependent upon how quickly action was taken. If you saw it immediately, and got it home quickly and dried it out using towels to soak up the rain water, most things would be okay.



Avoid flexing or bending the leather while you are restoring it because leather is weakened when the fibres are dry and it may crack.



Although water (hydration) is good for leather and is what keeps it in good condition generally when its fibres become over soaked they swell and become deformed. When they dry they may not shrink back to their original form and so become more brittle and distorted. Unfortunately at this stage it may be impossible to rectify.



Wet a towel with warm water, wringing out excess. Proceed to wipe the leather to remove any dirt and moisten the surface. If you are working on a large item, do one section at a time so you can apply Leather Masterâ„¢ Soft Touch (ex Vital) while the surface is still moist. This is not a conditioner per se; it contains polymers in an aqueous emulsion and is used to improve and maintain the tactile feel and lustre by rehydration and to ensure the leather remains matte, soft and supple.



Apply a small amount to a clean, damp 100% cotton micro fibre towel, use a circular motion and slight pressure to ensure the product permeates the dried-out pores, but do not push hard enough to damage the leather. Allow 20-30 minutes dwell time; unless the damage is severe, it should soften up after you massage it for a few minutes and then wipe surface with a dry 100% cotton micro fibre towel.





Associated Articles



1. “Reference sources and bibliography used for leather articles� - http://www.autopia.org/forum/autopia...ml#post1474865



2. “Leather Articles Hyperlinks� http://www.autopia.org/forum/autopia...yperlinks.html

[jfelbab]

A bit of cosmetic editing of the article is in order, but that aside you nailed it.

[wilfredes]

I also have the same problem, thank you guys.

[togwt]

A bit of cosmetic editing of the article is in order, but that aside you nailed it.

I’m glad this article was of some help.



I was going for factual, while maintaing asthetics to make it easy to read, I had not considered cosmetics … I’ll try harder