Rennlist - Porsche Discussion Forums - Finished Leather and the use of conditioning products

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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. Here is one definitive truth –you are dealing with the leathers finish, not the hide itself. The use of oils, replacement of fat liquor, oil-based conditioning, proteins or the adjustment of pH levels is totally unnecessary; the surface is a urethane that contains pigmentation (colour) it neither needs or benefits from any of the above

Unless a Premium Leather option was purchased Isocyanate based ethyl carbamate (urethane) finished leather upholstery is used by 95% as OEM in modern (post ’85) automobiles. It comprises a multi stratum acrylic and polyurethane resin binder system covering over the leather hide; the top strata are the surface pigmentation (colour) and an abrasion resistant urethane is used to improve flexibility, fastness and adhesion to the leather.
Half-life (t1⁄2 - a decay constant) [:is the time required for a quantity to reduce to half its initial value]
The half-life of urethane is usually considered to be five-years. However, this is dependent upon it’s exposure to climatic conditions

Two or three aqueous (water- based) pigmented base coat are applied, and then finally 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

It also has micro-pores that allow evaporation and hydration (the passage of water vapour through a membrane or pore) they are not sealed per se. Oils are not compatible with water-based pigmented urethane coatings and their molecules are too large to permeate, so they remain on the surface to be removed by clothing

So why would you need conditioning / what are you conditioning?

Finished leather seats consist of leather hide that has colours added (Pigmentation) and then top coated with a polyurethane/polyacrylic resin.Urethane hydrophobic (repels water) and, if it’s hydrophobic, then won’t it repel any ‘conditioning’ oils just as it repels water.

Wearing out the polyurethane/polyacrylic resin protective layer

The urethane clear coat on the exterior paint system is subjected to environmental abuse as well as the use of high alkaline car washes and machine polisher/abrasive compounds.

Whereas the interior upholstery is only subjected to the abrasion of driver/passenger entering/exiting. Yet vendors of auto upholstery conditioners would have you believe. Could this be the need to sell various conditioning products?