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, fat liquoring formulators, their chemists 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



(OEM) Technology



Automotive original equipment (OEM) technology is becoming more and more complex requiring educated and skilled technicians to work on them. As the materials used are constantly changing we must maintain our knowledge base and utilize the correct products and application methodologies to keep up with emerging technologies. It is very important to be able to recognise the various finishes and materials used as they all require different methodologies and products for proper care and maintenance.



A competent detailer never stops learning; knowledge of new technology and application methods also make detailer’s an asset to both a company and its clients and increase the value of the services offered. A detailer should know how to tell the difference between -

a) Single stage paint and a base coat clear coat paint system and be able to match the correct products to each system

b) Coated and uncoated aluminium wheels and what products to use for each finish

c) Finished and uncoated leather and the appropriate care products to use



Product choices



Diagnosis is the key, not guess work. Before deciding on what products to use, you need to ascertain the grade of leather and the type of leather finish applied.

There are a few different types of leather and several types of finishes applied to the leather used for vehicles upholstery. There are also a myriad of leather care products available, which need to be used in accordance to the type of and finish used in for your vehicles upholstery



Automotive leather is a rather difficult category to define as OEM descriptions of leather finishes vary, often incorrectly from that of leather industry manufacturer’s descriptions. Automobile manufacturers have blurred the distinguishing lines on what exactly constitutes leather and the ambiguity of the information provided by leather care vendors make the selection of the correct products for the types of finished leather used in automobiles very difficult.



One size fits all is a vendor propagated myth
.



History



Prior to 1939 leathers produced were solely vat dyed. Usually these colors faded quickly and developed into strange shades of greens or browns after exposure to the sun. Although the surfaces did not crack and chip as badly, the leather still became dry and stiff.



After 1945 new technology created new demands and brighter colors quickly became popular with the availability of nitrocellulose resin emulsion lacquers. Leathers that were vat dyed were now surface coated as well. In the early 1980’s nitrocellulose lacquers gave way to the resin-base dyes in use today.



Before 1980 most automotive leather upholstery used was high quality top grain full grain leather with a pigmented solvent-based Nitrocellulose lacquer coating and their unstable plasticizers would easily migrate in the heat from sun exposure and again create `fogging` on the internal surfaces of the windows. As a result of this plasticizer migration the use of oil-based products that contained solvents to keep them from becoming brittle and cracking, creams, waxes and oils were needed in aftercare products to try and bring the suppleness back into the leather



By applying an oil-based conditioner and allowing time for it to work in a heated environment. This can be accomplished by covering the seats with a plastic bag to help retain the heat and them leave overnight will ensure the oils permeate the lacquer and reach the leather hide. This process can also be used for equestrian tack; bridles, harnesses’, saddle and leather chaps and riding boots.



This nitrocellulose resin conditioning methodology for some reason has been carried over to modern finished leather. Even though urethane’s only requirement is to be kept clean and hydrated, it doesn’t require conditioning. Products such as leather (Saddle) soaps, oil-based Conditioners, Neat-foot oil, and Hide Food still prevail as top sellers, albeit most are made for equestrian tack. These are very different leathers with drastically differing care requirements. The exact reason for this type of misapplication is unclear.

It’s possible that there is an association with old world quality (i.e. European automobiles with unfinished leather upholstery and real burl wood interiors) with these types of products, despite the fact that the automotive industry has been using aqueous (water- based) urethane covered pigmented leather since 1980.



Modern Leather Surface Technology



Automotive leather surfaces have undergone major technological improvements over the past decade. The complex tanning process of chromed tanned hides results in the fat liquoring and oils necessary to keep the hide soft and pliable being locked in, this is further sealed by a durable urethane covering to protect the hide from abrasion, entering and exiting the vehicle well as the dust / dirt introduced by the vehicle’s AC system.



The leather used for modern automotive upholstery is finished leather; the ‘finish’ applied to the leather hide is a pigmented (colour) urethane protective layer and a clear abrasion resistant topcoat.



Unfinished vs. Finished leather



Unfinished leather - the appeal of this type of leather is its initial "natural" look and the soft, supple texture. The downside is aesthetic vulnerability; due to the porous nature of untreated leather, it stains easily and it is sensitive to ultra violet (UV) light, which means that the colour is subject to photochemical degradation (bleaching, (fading), discoloration, chalking, brittleness and cracking) all indications of UV deterioration. The porous nature of unfinished leather will allow a water- or oil-based solution to permeate the leather.



Finished or micro pigmented leather is commonly used for automobile as these resins create a film that protects the leather. The water-based urethane pigmented (colour) coat and the clear topcoat provides abrasion and stain resistance. This type of leather finish is the most durable and easiest to care for but tends to be stiffer than both unfinished and micro pigmented leather.



Using advanced micro pigments this finishing technique makes the finish rigorous enough to stand up to the conditions it would be subjected to in an automobile. Generally speaking micro pigment style leathers come in very earthy natural colours, incorporating a small quantity of pigment (a thin clear sealant that provides a uniform colour and affords some protection) but not so much as to conceal the natural characteristics of the hide so it will still retain the soft hand of Aniline leather. This type of leather is also used for perforated leather finishes.



Automobile model ranges use different materials for their vehicles interiors; there are also various finishes applied -



• Aniline Leather (Immersion Dyed)



• Semi-aniline (Micro pigment) leather



• Finished leather[/COLOR]



As well as various grades of leather hide, full-grain, top-grain and split –grain, along with artificial leather such as MB-Tex and unfinished materials like Synthetics and Alcantara, and sometimes combinations of products (Alcantara seat inserts on leather seating) Using any product not specifically designed for your leather finish can cause staining and permanent damage.



1.Unfinished leather - leather that has had no surface treatment added; leather dye is applied by soaking the hide in the desired colour so that it permeates the hide. But due to the interior environment unprotected Aniline is rarely used for automobile upholstery. There is no urethane coating that will crack, however it will likely fade, wear and get stained. Stains can be very difficult if not impossible to remove depending on what the stain is and how long it has been there.



2. Finished leather - during the finishing processes - the final stages of the tanning process, various finishes can be added to the surface to make it more serviceable or to hide defects and scars in the hide’s surface. Leather pigmentation or colour is applied to the leather usually as a coloured urethane coating.



The applied finish - consists of two or three aqueous (water- based) pigmented base coat applications, and then a clear aqueous (water- based) top coat is applied as the final stage of the finishing process, which usually includes additives to give it a soft feel (patina) and abrasion resistance, as well as a limited amount of ‘slide’ to assist in entering and exiting the vehicle



Cross-linking enhances the physical properties of water-based pigmentation (colour) and the urethane coating, which proceeds to form a chemical bond between the molecules, creating a resilient and very durable finish.



Topcoat - an extremely hard wearing water-based clear urethane is used to improve abrasion resistance and colour fastness, making the surface much easier to clean and less prone to staining, while increasing resistance to perspiration, grease and oil. It greatly increases surface durability and also improves surface texture giving it a smooth, soft and silky feel.



It also has micro-pores that allow transpiration, i.e. evaporation and hydration (the passage of water vapour through a membrane or pore) they are not sealed per se. Urethane pigmented finished leather won`t absorb liquids because of the protective properties of the finish making for easier clean-up.





A simple test - place a drop of moisture on the surface of the leather - if it soaks into the leather you have unfinished leather (sometimes called aniline style)



If there is a very light color or clear coat on top of aniline-dyed leather, it is often referred to as "semi-aniline." Semi-aniline leather offers modest protection while retaining much of the aesthetic beauty of unfinished aniline-dyed leather but still remain absorbent to moisture. If the moisture sits on the surface and does not soak in and darken the material you have finished leather.







Section through leather upholstery - Diagram by Advanced Leather Solutions



Be cognizant that you’re dealing with the finished coating on the leather and not with the leather hide itself



Automotive leather and finished leather surfaces have undergone major technological improvements over the past decade. The leather used for automotive upholstery is finished leather; the `finish` applied to the leather hide is a pigmented (colour) urethane protective layer and a clear abrasion resistant topcoat.



This type of leather has an aqueous (water- based) urethane pigmented (coloured) coating, think of it as a urethane paint applied on top of the leather, and then a clear top coat is applied, o you are not actually touching the leather. The coating gives the leather more durability and protection. It is also much easier to clean. Finished leathers make up almost all auto leathers. Just because leather has a top coat doesn`t mean it is any less desirable.



It also has micro-pores that allow transpiration, i.e. evaporation and hydration (the passage of water vapour through a membrane or pore) they are not sealed per se



Pigmented leather won`t absorb liquids because of the protective properties of the finish making for easier clean-up. Since the leather hide has a clear coat finish, when treating the leather, so you are in fact dealing with a urethane (to all intents and purposes, a ~150 (micron) thick plastic surface coating, about the same thickness as automobile clear coat paint; that simply needs to be kept clean and hydrated ...it really is that simple.



A simple concept that been stated a million times and still some will swear that treating finished leather with a conditioner is beneficial. But if you feel $50 plus and approx 2-3 hours work is a worthwhile investment of time / money to clean a urethane pigmented covering, that’s your choice



I hope you’ve found this article both informative and helpful.




TOGWT Autopia Detailing Wiki Articles



1. “Proper Finished Leather Cleaning and Care” -http://www.autopia.org/forum/guide-d...ning-care.html



2."Leather Upholstery Type Surface Identification" - http://www.autopia.org/forum/autopia...fication.html#



3. "Leather Articles Hyperlinks" -http://www.autopia.org/forum/autopia...yperlinks.html







If you have any questions about automotive leather, its care or renovation techniques, please let me know