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Leather Conditioning


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#1 TOGWT

TOGWT

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Posted 30 August 2011 - 02:03 AM

Many of the following statements are controversial and are polar opposite of popular leather care practices recommended by product manufacturers. I've found that some leather care myths are deliberately perpetuated by the industry, especially those on the use of oil-based leather conditioners and others are just common errors of judgment.

Modern (> 1990) automotive finished leather upholstery used by 95% of OEM has multi- strata finish, the actual hide which must be kept hydrated to maintain tensile strength, elasticity and suppleness to prevent the hide from cracking and becoming dry. Within the top strata (urethane) which provides protection from abrasion and the surface coloring (pigmentation) which can wear off from normal use. This can be exacerbated by oils from the skin and grit, both of which act like an abrasive and can wear a hole in your bolsters and arm rests if you don't keep the surface clean. Finished leather s only requirement is to be kept clean and protected, urethane doesn’t require conditioning

Avoid using any product that seals or renders finished leather water-proof, this includes most of the newer polymer or silica coating type products as they will not allow hydration (transpiration and evaporation of moisture)


Leather Care

Understanding leather care products and how to usethem is essential; obtaining accurate technical information on automotive care products can be problematic, but detailer’s should be knowledgeable on the dressings sold for leather, vinyl, tyres, rubber, and their chemical content. Otherwise they are at the mercy of a biased supplier to provide not only products, but also the technical knowledge and application methodology regarding product usage.

Unfortunately not all suppliers or distributors have the ability or technical knowledge to provide accurate information; some do not want to divulge what they term ’trade secrets’ as the information might be detrimental to their product sales or company image. Honest opinion or merely advertising? Commercialism brings with it concerns of honesty and true representation. In other words, it’s difficult to know what is true when someone is motivated by income, i.e. directly targeted at product sales, more so than an unbiased opinion

Automotive leather care is a subject surrounded with misinformation and myth, products such as leather (Saddle) soaps, oil-based Conditioners, Neat’s-foot oil, and Hide Food still prevail as top sellers, albeit most are made for equestrian tack, Leatherequi, an oil-based product is also a very popular, that is used in a market that is dominated by pigmented leather with an acrylic water-based polythene protective covering; which are very different leathers with completely differing care requirements.

The exact reason why this is the case is unclear. It’s possible that there is an association with old world quality (i.e. European automobiles with leather upholstery and real burl wood interiors) with these types of products, despite the fact that the automotive industry has been using water-based polyurethane covered pigmented leather for many years

How your leather feels
(its Patina – literally ‘hand’) tells you more about its condition than anything; it should feel like something between velvet and satin, supple, inviting and luxurious. Leather care starts with maintaining factory fresh feeling leather from the beginning. Keeping it clean is important, and hydration is the key; preserving the life, flexibility, appearance and longevity of your leather.

Definition of Leather conditioning

Not all conditioners are alike; some are aqueous (water- based) as opposed to oil-based, some are an emulsion of oil and water. Some use a solvent as a carrier system and when applied to the leather surface, it appears to “soak in”.

a) Proteins, collagens and oils cannot permeate the leather and therefore remain on the surface; the same thing will apply to seating surfaces; the problem will be exasperated as the oil will attract dirt/grime to the surface. So the claims of strengthening and nourishing the leathers fibres are groundless as the oils cannot permeate the leather and therefore remain on the surface; the same thing will apply to seating surfaces; the problem will be exasperated as the oil will attract dirt/grime to the surface.

The finished leather used in automobiles is removed from a dead animal and then is subjected to a tanning process. Why would a deceased animal skin (hide) require proteins and collagens, these types of proteins are used to ensure a healthy and elastic dermis and to ensure the tendons remain supple in living tissue.


B) When leather tanners talk about conditioning leather they are referring to re-hydration; not the replenishment or replacement of the fat liquoring oils and waxes. The only 'conditioning' required for finished leather upholstery is hydration; oil-based products cannot permeate the finish leather (urethane pigmentation and / or covering) that is used in 95% plus of modern automobiles.

Modern leather needs to be kept hydrated with moisture to ensure the leather remains flexible and maintains its soft tactile feel. The oils cannot permeate the leather and therefore remain on the surface; the same thing will apply to seating surfaces; the problem will be exasperated as the oil will attract dirt/grime to the surface. This is done by regularly wiping the surface with a damp 100% cotton micro fibre towel and by using aqueous (water- based) leather care products. There is no reason to use oil-based leather care products to condition or feed leather hides

Aqueous (water- based) products are able to permeate deep into the hide, unlike oil, due to its larger particles, whereas water particles are smaller than both oil and the molecules of urethane, which enables aqueous (water- based) products to permeate and provide hydration, which is essential for suppleness recovery.

In summary, an aqueous micro emulsion is readily absorbed into the fibres and provides lasting and effective lubrication without migration, while re-hydration leaves leather feeling silky soft and pliable.


Particulate size - you can tell how small the emulsion droplets are and in some cases how concentrated an emulsion is by its colour. Opaque white emulsions typically have a large particle size, while faintly opaque or pearlescent emulsions typically have a small particle size approaching 1µ or less.

Water - unlike other organic or hydrocarbon-based solvents, is non-flammable, odourless, non-toxic and non-sensitizing to the skin and it doesn’t impart a greasy or tacky feel to the surface of the leather.

Leather is hygroscopic and so moisture is the most important element (median15 %) in the care of leather; all changes in leather are due to moisture differences. Too little moisture (< 10%) will cause the leather to become hard and inflexible, too much (> 20 %) and it may the fibres to swell and may cause mould formation.

Be cognizant that ‘too much of a good thing can be bad for your leather’ if your leather becomes saturated with water it will dry and the hide will become hard and inflexible. The original Roman armour and shields were made from leather that was first soaked in water and then left to harden in the sun


Oil-based Conditioner

I have discussed this issue with many people in both the leather tanning and leather care products industry and some specialised industrial chemists who have worked in the leather manufacture and care industry for 35 plus years. As specialists in leather care they had a much better understanding of what the ideal product is for maintaining finished leather surface used in automotive leather upholstery and i asked the following questions.

(a) How much conditioner will get through the cross-linked urethane coating on the leather?

(B) A chrome tanned leather hide is sealed at the tannery and then pigmented; what could a conditioner do for the hide?

We discussed the product s that are currently being used and the consensus was that many of the products simply were not suitable for the current finishes used for automotive leather

I looked at a detailing care product vendor site and found nine pages of leather care products, mostly expensive oil-based leather ‘conditioners’ this could be the reason they ignore an appropriate care product for the upholstery material actually used for automotive (finished leather) upholstery.

1. How much conditioner will permeate the urethane top coat on a sealed pigmented leather hide? Chrome tanned leather hide is sealed at the tannery and then pigmented; what could a conditioner do for the hide?

2. If oil is allowed to permeate any micro fissures in the leather or via the stitching it will travel laterally compromising the resin binder system which will delaminate from the hide releasing its adhesive bond. It will then be able to move in a different direction from the hide, which will result in surface fissures and cracking, further compounding the problem eventually leading to the subsequent replacement of the protective covering

3. 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 polyethylene covering to protect the hide from abrasion from clothing as well as the dust / dirt introduced by the vehicle’s AC system.

4. The complaint that most leather conditioners are "greasy" is typically attributable to the use of Lanolin. On most leather conditioners the containers label warns against its use on steering wheels as it will make them slippery and unsafe. The oils cannot permeate the leather and therefore remain on the surface; the same thing will apply to seating surfaces; the problem will be exasperated as the oil will attract dirt/grime to the surface


Many so called leather conditioners utilize chemical solvents in order to facilitate penetration of the oils into the urethane covering or the pigmented leather. Most covered leather finishes are water -based and so any solvent or alcohol can begin to cut through them, even if you go over it and you see no colour come off, you have probably compromised the clear protective top coat and possibly the leather’s pigmentation (colour).

Solvents will soften the protective covering, which can get tacky very quickly, attracting abrasive dust/dirt and will eventually wear through as it does not have the durability found in the topcoat. What happens when the solvents vaporise - polish and many surface protection products are formulated with oils to enhance the surface or to nourish leather surfaces, neither of which is necessary?

A urethanes fibre structure will stretch in all directions with no particular grain or stress pattern. The urethane surface coating will not withstand multi directional stress, however, and when it’s flexed or stretched continuously in the same place the surface coating develops minute cracks. If oil is allowed to permeate any micro fissures in the leather or via the stitching it will compromise the resin binder system and delaminate from the hide releasing its adhesive bond, and it will be able to move in a different direction from the hide, which will result in surface fissures and cracking, further compounding the problem eventually leading to the subsequent replacement of the protective covering

In summary, an aqueous micro emulsion is readily absorbed into the fibres and provides lasting and effective lubrication without migration, while re-hydration leaves leather feeling silky soft and pliable.


Feeding Leather

[Zymol Treat Leather Conditioner is a solvent-free, banana-oil and collagen-based feeding product that releases trapped solvents and restores moisture to keep your leather looking, feeling, and smelling like new. Helps to reduce the aging process in leather upholstery and trim] Zymol Marketing

Older (50 and 60’s) automobile upholstery leather and exterior paint was finished with Nitrocellulose lacquer and required oils for it to remain flexible otherwise it would crack. This is where the ‘feeding’ paint / leather comes from

Leather is the hide removed from a deceased animal and the tanning / curing processes used seal in the necessary oils during the fat liquoring stage, thereby ensuring that the fibres cannot nor, do they need to be fed. Hide foods are something again that can be used in the horse and saddle business or with the older Aniline type dyed leathers.

There is no correlation between how we look after our own skin and how we look after finished leather upholstery, Proteins, Collagen, Lanolin and Aloe are used for human skin reconstruction and nutrition, leather is not like human skin, its dead and cannot be regenerated or revived. The finished leather used in automobiles is removed from a dead animal and then is subjected to a tanning process. Why would a deceased animal skin (hide) require proteins and collagens, these types of proteins are used to ensure a healthy and elastic (living) dermis and to ensure the tendons remain supple.

Many leather treatment theories have grown up around the fact that you need to moisturise skin and so this is wrongly transferred to the care of finished leather, especially when you consider that it has a urethane pigmented coating

Fat liquoring

All cowhides are naturally oily, unfortunately, these natural oils are stripped away in the tanning process (tanning is a process using a water vat and chromium salts to preserve hides and prepare them to absorb dyes) and some equivalent oils must be re-introduced after tanning. This step, the replacement of oils, is called fat liquoring.

[Fat liquor is not volatile nor migratory, so leather is not going to lose it. However, along with the fat liquor, the other critical factor is moisture. Any leather is going to lose its moisture in a hot car. Although leather seems dry, it is not. Of course too much moisture quickly leads to mould and mildew problems, so soaking it down is not reasonable. Ideally, exposure to a humid atmosphere will help balance the effect of over drying on hot days. Leather is very dynamic with respect to moisture content, meaning moisture comes and goes easily under normal circumstances....] American Leather Chemists Association (ALCA)

Connolly Hide Care

Made by Connolly Brothers, established since 1878, a leader manufacturer of leather tanners and curriers, this cleaner/conditioner made of lanolin (a natural substance used in soaps, cosmetics, and ointments) is the best leather protector in the market, recommended for cleaning and preserving Connolly Hide, upholstery, clothing and leather goods. This has been known to be the leather conditioner of choice by European automotive enthusiast. For use on Nitrocellulose lacquer coating, applying once a month would give the fine look and keep the finish soft and clean.

“Connolly Hide Care is a traditional lanoline based bees' wax treatment for fine leather goods, upholstery and clothing. It moisturises and feeds the leather prolonging its life and restoring suppleness” This leather care system is based on 10 – 15 year old technology


Leatherequi Pristine Clean and Rejuvenator Oil

Here is a little of the manufacturer info:

[Leatherique Pristine Clean and Leatherique Rejuvenator Oil work with a capillary action. The proteins, cleaners, and conditioners find their way deep into the natural pores of the leather and force out the dirt, perspiration, air pollution, and other toxins that dry out and destroy the fibres of the leather, depleting the fibres strength and flexibility, and causing them to deteriorate...

The enriching formula, once bonded with the spongy leather fibres, continues to nourish the hides for several months. On cardboard hard leather, several applications may be required. Then for maintenance, use one application 2-4 times per year.

Prestine clean is a natural, gentle ph correct cleaner that is formulated to be a perfect stand alone cleaner for maintenance dusting and detailing of all the leather, vinyl, PVC plastic, and is also wonderful to soften black rubber trim on seals, as well as keeping your tires clean and plump without the glazed donut look.

Although it was named Rejuvenator Oil by founding fathers, Ty Peck and George Pavlisko, Sr., this product actually contains no fillers such as mineral oil or petroleum products as Lexol and other products do.

The formula is based on a natural Old Swedish secret and is a complex blend of proteins and collagens that actually restore the tensile strength to the leather.

Our Rejuvenator does not just sit on top of the leather making it slick and greasy, nor will it be absorbed into the stitching to rot it as commercial products do]
Leatherequi

[After the ph correct proteins and collagens from the Rejuvenator Oil have permeated back into the pours and fibers of the leather, strengthening and nourishing them, the surface may be tacky, sticky, gritty, or have a white haze. This is simply the dirt, grime, air pollution, perspiration, salts and other toxins that have floated out of the leather to the surface. Apply Prestine Clean by putting it in a Spray Bottle then wipe off with a SOFT lint free cloth]
Leatherequi.

The idea of applying the conditioner, allowing time for it to work in a heated environment, before it can be cleaned off which is then rewarded by the rather odd fact that you have to then clean the leather in a secondary stage is really rather odd, and is reminiscent of the Saddle Soap process, before it can begin to clean it must first dissolve its own oils, which limits its capacity to dissolve dirt and oils in the leather, and I can see no technical reason for applying a product in this way.

Top-grain premium leather is mostly used in prestige European automobiles; Aston Martin, Bentley, Ferrari, Jaguar, Lotus, and Rolls Royce, US Cadillac and high-end German automobiles such as; Audi, BMW, Daimler AG, Mercedes-Benz, and Porsche, for most of these vehicles premium leather is standard OEM specified equipment, but for most it’s a ‘premium’ package that costs upwards of 2,000 USD . This is the niche market sector both Leatherequi and Connolly were originally formulated for.

When I first started detailing five decades ago at my Father’s BMW, Mercedes-Benz dealership the seats were made from a natural leather hide that used a solid pigment mixed with a cellulose lacquer coating, which are very absorbent and dried out quickly. If you looked carefully there were slight differences in colour and the way they felt (patina) as the OEM did their best to colour match them. They now use finished leather with a pigmentation added to a thin clear sealant that provided a uniform colour and abrasion resistance

Modern automotive finished leather upholstery used by 95% of OEM is a multi strata covering over the leather hide; pigmentation (colour) and an abrasion resistant urethane. Finished leather s only requirement is to be kept clean and protected, urethane doesn’t require conditioning

An acrylic and polyurethane resin binder system is used to improve flexibility, fastness and adhesion to the leather, then two or three aqueous (water- based) pigmented base coat applications, and then a clear aqueous (water- based) top coat is applied, which usually includes additives to give it a soft feel and a limited amount of ‘slide’ to assist in entering and exiting the vehicle as the final stage of the finishing process.

Always keep in mind that you’re dealing with the finished coating on the leather and not with the leather hide itself
The finished leather used in automobiles is removed from a dead animal and then is subjected to a tanning process, which effectively seals the hide’s fibres. Why would a deceased animal skin require proteins and collagens, these naturally occurring / regenerating proteins ensure a healthy and elastic dermis and to help to ensure the tendons remain supple.

Any leather conditioner is likely to make urethane feel softer as they all tend to soften up the polymer (urethane) coating; the problem is that due to their molecular size they cannot permeate the urethane, although oils can seep through the stitching. These so called conditioners act to trap dirt, perspiration, and anything else within the coating that commercial products leave behind and are then absorbed onto clothing. The only thing that can evenly permeate finished leather is water vapour

Oil-based leather care products can cause the urethane covering to be compromised by permeating the stitching, cracks and fissures and cause the urethane and the leather surface to delaminate, as the oils negatively effect the adhesive used

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.

But if you feel $50 and approx 4 hours work is a worthwhile investment of time / money to clean finished leather with a thin urethane pigmented covering, that’s your choice (See also article Oil and oil-based Products)



[EDIT: Leather Condioning Definition - added 02.12.2012]

Edited by TOGWT, 11 July 2012 - 05:10 AM.

Detailing Art; where applicable Chemistry meets Aesthetics See Autopia Detailing Wiki




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