Difference between revisions of "Leather quality"

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Leather quality

It is easy to identify the vast differences in skin quality that exist from one species to another. However, variations also occur even between animals of same race, same gender, who are of the same age and have similar nutrition , and even within a skin of one animal. Leather is a natural product and therefore not always equal in quality. Differences mainly occur due to the gender of the animals, their age, nutrition, feeding and general animal keeping practices. Below we have laid out how some of these factors can affect skin quality.

Differences in quality of cow leather (but also applies to other species):

Age: The quality of hides from older animals is generally worse than that of younger animals.
Gender: Females have a denser fibre structure and a finer grain structure.
Gender specific activities: The more often a male animal was used for impregnation and the more often a female animal gave birth, the worse is the stability of the fibre structure of the skin. Castrated oxen tend to have finer skin structure.
Nutrition: Fresh forage promotes better quality skin.
Animal keeping: If an animal is kept on open pastures, the texture of the skin is better.
Climate: A harsh and cold climate favours a good skin quality.

Leather is used for many different applications. As car leather, for shoes, for leather straps and belts, for leather suits or buttery soft leather gloves. Diverse set of demands are placed on leather depending on its use. Furniture leather should be easy to maintain, but should also be soft and warm. Shoe leather should be waterproofed, soft, retain heat and robust, yet also remain breathable. A car leather should be easy to maintain and should be impervious to heat, cold and wear.

In all applications, it should not tear, it should be easy to clean, it should not bleach, it should not smell unpleasant, it should not contain pollutants and it should be durable. All these parameters are summarised as "leather quality" or "leather properties".

In reality, many parameters of the leather properties are in conflict. Leather can`t be soft, robust and easy to clean and maintain at the same time. Leather can't be paper thin and soft and also tear proof at the same time.

In particular, the sensitivity of especially high quality leather like soft aniline leather of a luxury leather jacket, of exotic leather or of an expensive set of furniture are often misjudged. Especially because the object was so expensive customers expect that it would be very easy to clean and maintain the leather. But the reality is the opposite. Such valuable leather has the sensitivity of silk. With regular use the beauty diminishes rapidly, and incorrect cleaning can even ruin the material.

A good leather feels warm and soft, but is also more sensitive.

Particularly car leather is considered to be robust. Most of the vehicle manufacturers require more than 40 quality criteria that must be fulfilled. Stringent wear tests must be passed. It must be resistant to suntan lotion and bug spray. Many chemicals are not allowed to be used and leather emission is tested. As a result, the leather is extremely durable, but no longer soft and warm to touch.

The tanner and the producer of a leather object therefore should establish their own, verifiable quality parameters depending on the desired properties of leather. The consideration of these parameters starts with the selection of the animal species and the rawhide. Also during the subsequent processing, the differences in the quality of the individual sections of a skin including the possibility of skin damage when cutting must be considered. Only a limited quantity of skins can be worked upon at any given time during the manufacturing process of leather and all of them do not behave the same in each run. Often the tanner is required to intervene and make minor changes, which can lead to deviations from one batch to another. Differences can be detected depending on the quality control limits set.

Apart from the production quality, the longevity of leather depends on certain other factors too. An important element for long lasting pleasure of a a leather object is the handling of it. If leather is regularly cleaned and maintained and not excessively overused and if the basic rules in dealing with leather are respected, you will prolong the enjoyment of this durable and robust material.

Leather testing - leather properties

To evaluate leather properties there are many different parameters and test methods. For a layman, only rough and basic testing options are available when purchasing a good and beautiful leather item. Some of the criteria can be checked directly as an end customer, but when certain criteria cannot be tested, it always helps to direct the correct questions towards the vendor. Below we have laid out some basic checks that can be carried out.

Look of the leather: A beautiful top quality leather looks very natural and does not contain markings on the surface.
Leather grain texture: The grain texture should be good looking and should be as natural as possible. An embossed grain pattern is very uniform, which does not correspond to the natural grain of a skin and embossed leather often feels less natural.
Softness of the leather: Generally, leather should be soft to touch and have a natural feel. But leather shoes or leather belts require a certain strength.
Haptic evaluation of leather surfaces: A firm leather, as well as all other leather should feel good. This does not include only the softness. A leather can also be expected to feel blunt or smooth. The more beautiful leather feels, the better is the quality of the leather.
The leather finish: To protect the leather, it is often useful to apply a binder based finish on the leather surface. The more layers of leather paint are applied to leather, the more unnatural it feels. If the grain texture sanded before the finish, the leather feels even more unnatural. Also a film coated leather is less natural, and usually considered to be of inferior quality in comparison to natural leather and therefore relatively inexpensive. But for a patent leather, this effect is an accepted feature.
Breathability of leather: An advantage of leather over alternative materials is its breathability. But the more a leather is coated with leather colour or a film, the lower is the breathability.
Tear strength and stability of the leather: Good leather is stable and resistant to tearing, whereby suede and nubuck or extremely soft lambskin cannot have the same stability as a belt leather. But within the types of leather there are very different qualities and an inferior quality leather within the same type of leather will always tear more easily in comparison to the higher quality ones. Also sanded leather is usually less stable than full-grain leather.

Criteria of quality leather

To determine whether a leather corresponds to the desired quality requirements, it passes through a series of testing processes. Extremely high and strict standards are set particularly in the automotive industry. Minimum qualities are set and controlled also for furniture, shoe and garment leather . In addition, there are statutory testing regulations for harmful substances, which is also a sign of quality.

In the manufacturing of leather, the leather quality is constantly checked with all senses and with test equipment.

Although the specific test standards vary by manufacturer and are chosen according to the intended use of the leather, the tested properties are quite uniform.

Further rules on permitted ingredients in leather are regulated by national laws.

Test criteria for the leather quality include (and is regulated in many national and international standards):

Breathability: The ability to absorb sweat and to submit it to the opposite side.

Weight: Important e.g. for aircraft leather, because it should weigh as less as possible to reduce fuel costs.

Thickness of leather: The thickness has an influence on the stability of leather.

Tensile strength - Tear strength: If the leather is drawn (for example, more than 200 N per 5 cm).

Tear force: Leather should not easily tear further (for example, desirable: more than 20 N).

Adhesiveness of the finish: The colour layers on the surface should not come off (for example, desirable: more than 25 N per 5 cm).

Flammability and fire retardancy of leather: Important for aircraft, nursing homes, public buildings etc.

Flame-retardant leather.

Rub fastness: Dry, wet, alkaline. The surface should not change in friction or wear zones.

Light fastness: Leather should not fade.

Flexibility: Desirable: robustness in more than 100,000 cycles. Leather should be extensible, but not baggy.

Buckling behaviour: Leather should not break in folds. Desirable: 30,000 folds without damage.

Water permeability: Leather should be waterproof.

Acid and alkali resistance: The leather surface should be resistant to as much as possible chemicals.

Hydrolysis resistance: Leather should not decay caused by humidity.

Haptic: Leather should feel accordingly as desired.

Climate Alternating Test: Leather should be weather-resistant.

Degree of gloss: Leather should have the desired degree of gloss.

Back polishing: Leather should not lose the desired gloss level in use.

Soiling behaviour: Leather should not easily get dirty.

Creaking noise: Leather should not make undesired friction noise when moved.

Smell: Leather should not smell or it should smell acceptable.

Leather emission: Leather should not evaporate any substances.

Alcohol resistance: Drop Test. Resistance to e.g. disinfectants.

Sea water resistance: Resistance of boat leather to sea water.

Usually material destructive tests are necessary to check the leather quality. - Samples are punched out of the leather.

The extensive testing standards set by manufacturers meanscar leather is very similar and uniform across board. Most are monochrome, surface-coloured smooth leather.

Standards of quality leather

There are countless national and international standards to determine the quality of leather. Also, the labelling of leather products is regulated by national and international standards. Additionally, many leather manufacturing and processing companies have extra internal standards and requirements.

Overall, the standards set for the quality of leather are correct and necessary. But they are also filled with a lot of grey areas, loopholes and weaknesses.

In Europe, confusing rules exist on labelling of split leather. In some cases, it is required to declare and designate the type of leather and in some cases it is not. In Germany for instance, coated split leather is used in vehicles, without the obligation to inform the customer. An end user cannot differentiate between the two, When the surface of split leather is embossed with a grain structure it is virtually impossible to tell the difference. In such cases, the standards must do more to ensure transparency, so the customer knows exactly the type of leather they are getting.

Standards are often referred to find a verifiable solution or reach verdicts in legal disputes. However, they are inconsistent, ambiguous and open to interpretation. They do not mention when one particular rule or standard should take priority over the other. An end consumer must be able to find out the quality of the material and be able to compare prices and qualities. The leather standards and norms must do more to protect the end consumer by ensuring dealers, manufacturers provide clear transparent information.

Test equipment

To test the various requirements for leather, there are a wide variety of test devices.

VESLIC rubbing test: The rubbing test checks the dry abrasion and wet abrasion qualities of leather. Wool felts are rubbed dry and wet in a specified number of times over the leather. The wear in daily use and the prone to discolouration is examined.

VESLIC rubbing test.

Leather flexometer test: This test examines resistance of the leather to wrinkles. Folding the leather multiple times in all directions allows it to test its resistance.

In particular, shoe upper leather gets buckled during walking and needs a special resistance to breakage. The "Bally Flexometer" named after its inventor is a commonly used instrument and method to test resitance. It is also used for car leather, furniture leather, clothing leather and other leather applications.

Bally Flexometer

Taber abrasion tester: The Taber abrasion tester checks resistance of various materials. The Taber Abrasion test is an internationally recognised test method. Abrasion resistance is tested using two friction rollers that are pressed with a predetermined force to the test material which circularly rotates below the friction rollers. Thereby, simulating a combination of scraping, sliding, squeezing, thwarting and abrasion.

Taber abrasion tester

Martindale method: The Martindale rub test examining the abrasion resistance of upholstery leather.

Martindale rub test - Martindale method

The ball plate test simulates selective frictional stress.

Light fastness - Xenon tester: The xenon tester validates the effect of light on surfaces. Sunlight causes rapid aging of materials. In the test, a xenon arc lamp is used as a radiation source, wherein the filtered spectrum has similarity to the sunlight. The xenon test is suitable for all paints, textiles, plastics etc.

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Light fastness test - Aniline leather and semi-aniline are natural and soft, but fade more easily.

The change in colour can be checked with measuring devices. The scale of difference is measured in delta value. Delta DEcmc is a number that represents the distance between colours. The difference in colour depends mainly on two factors: 1) the variation in brightness and 2) The tone of the colour itself. For example, a leather can turn from blue into green, without noticeable changing in the measured brightness. A variation tolerance of delta value of 1 is usually considered acceptable. However, the automotive industry requires a maximum Delta of 0.5, which is difficult to achieve. Surface irregularities of the grain texture or different degrees of gloss can also change the Delta value. Even within an area, the delta value can vary up to 0.5 due to differences in the grain texture.

Photos below show a deviation in Delta DEcmc of 6.6 because of fading following a Xenon test

The Xenon-tester shows the light sensitivity. The finish is recognisably faded. DEcmc 6.6.

Aniline leather day 0, day 16 and day 50 - faded in daily sunlight.

Quality differences

It is difficult to judge the quality of leather for the end consumer with virtually no experience. Even an expert will not be able to identify and recognise every defect with their naked eye. Experience is needed to discover differences in quality and majority of quality criteria can only be tested in the laboratory.

The aim and purpose of this dictionary is to help people understand Leather. For buying furniture, we have an extra instruction.

Price and quality go hand in hand. If a leather object is particularly inexpensive, in most cases it's not valuable. Branded products usually perform extensive tests to ensure the quality of their goods. Manufacturers who evidently endeavour to improve the quality of their products and to describe the origin and quality of the leather, usually have a good quality end product. This also applies to established dealers.

Leather in vehicles have quite rugged qualities due to the purchasing power and strict quality controls performed by manufacturers. The leather is not particularly soft and natural, but highly durable. Furniture leathers have greater variation in quality due to the large number of vendors.

Even if the leather is of good quality, over time due mainly due to wear, the top layer of colouration rubs off. The leather itself remains undamaged. However, if the leather itself is unstable, it deteriorates under the colour layer and the colour binder alone cannot compensate for this lack of stability in the fibre composite.

Typical wear in car and furniture leather with good quality.

Typical breakage in leather with poorer quality leather.

In order to be able to assess whether a leather damage is a quality deficiency or typical aging behavior of leather, many aspects have to be considered. No leather is immortal and depending on the leather type, type of usage and load, intensity of maintenance and age of the leather, a leather damage can be typical aging behavior or a quality deficiency.

Variations in quality

We have already identified how the quality of leather can vary drastically, depending on the section of the hide. Therefore, it may happen that different leather qualities appear within a leather item. This is often seen in furniture and clothing.

Furniture leather where adjacent areas have different qualities and therefore aged differently.

Furniture leather with different fading behaviour.

Car headrest - even when equal pressure is applied within different areas of the same leather, varying number of wrinkles appear. In the border region loose grain leather gets visible.

Types of leather - Leather quality - Ease of maintenance

Most assume that the best quality leather would be the least sensitive and easiest to maintain. But as with textiles or precious metals (silk is very sensitive and gold is not scratch resistant) is the sensitivity at the highest price and quality segment rather higher. Valuable objects often require more and better care than cheaper items. This also applies to the different types of leather.

Comparison of leather quality and ease of maintenance.

Suede - Nubuck - Aniline leather - Semi-aniline - Corrected grain - Coated split leather

Remarks:

Why is Aniline leather, nubuck and suede less easy to maintain? They are porous leather and therefore more sensitive to stains.
Why is Aniline leather evaluated with best quality? Because aniline leather is especially natural and warm.
Why is coated split leather less easy to maintain? It is more unstable, what cannot be improved by care and classic leather care products harms some types of split leather coatings.
Are there exceptions to the rules?

LEATHER QUALITY: An aniline leather could theoretically unexpectedly tear or have an undue smell or the leather colour might rub off. Then it is of poor quality. A smooth leather can be fine sanded and carefully embossed and feel like a semi-aniline leather. Then it may be better than a normal, pigmented smooth leather.

But in most cases, the leather corresponds to the expectations. Aniline leather is more expensive because hides without skin damages are rare. Therefore, more effort is applied in manufacturing of such leather.

EASY-CARE: Every type of leather has its own qualities. As long as the information provided by manufacturers and dealers at the outset is accurate, the leather should adhere to its usual qualities. Problems may occur when cleaning and maintenance if the leather is genuinely of a poor quality. But this is seldom.

Conclusion: Semi-aniline and pigmented smooth leather are the golden mean for leathers in constant use. They are comfortable, natural and easier to maintain as the remaining types of leather, but also cost a bit more. For price conscious buyers corrected leather is a good choice.

Additional information

WE UNDERSTAND LEATHER - WWW.COLOURLOCK.COM

@@ Line 87: / Line 87: @@
 * '''[[Thickness of leather]]''': The thickness has an influence on the stability of leather.
-* '''[[Tensile strenght - Tear strength]]''': If the leather is drawn (for example, more than 200 N per 5 cm).
+* '''[[Tensile strength - Tear strength]]''': If the leather is drawn (for example, more than 200 N per 5 cm).
 * '''Tear force''': Leather should not easily tear further (for example, desirable: more than 20 N).

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