A common customer complaint6 February 2002
Peeling of the finish during use is a frequent customer complaint, particularly in domestic upholstery leather . Sometimes the entire finish peels away from the leather surface, but more commonly it is an inter-coat adhesion problem.
The cause If the finish is peeling away from the leather surface, it may be caused by a lack of wetability of the leather, for example due to an excessive amount of fatliquor or silicon containing compounds on the surface of the leather. Alternatively, it could be a result of too large a particle size of the finish. A lack of penetrator in the formulation will also give rise to poor adhesion. Inter-coat failures can also have several possible causes: * Over spraying. * Over-sealing of earlier coats. * Deterioration of the finish by inappropriate cleaning or accidental contamination of the leather in use. * Finish sticking. Over spraying, ie the application of two finishes, is sometimes done to correct a problem with the original finish, eg to match the colour better or to rectify a problem with the finish curing. However, modern leather finishes often contain a significant amount of silicon, which in use improves their performance, but does present problems with non-adherence of over sprayed finish coats. Over sealing of coats can be avoided by ensuring that intermediate plating is not too heavy. Tacky finish can cause the finish to be pulled off if it becomes stuck when the leather is in a pile. Apart from occurring if the finish has not been dried properly before piling, it can also result from finish formulation problems such as an excess of binder or too soft a binder. Insufficient wax is another possible cause. Of course, not all peeling problems are the fault of the tanner, sometimes misuse of the leather can result in a finish failure. Accidental contamination by substances harmful to the finish, eg nail varnish remover, can occur and cause localised peeling. More extensive damage can occur if the leather has been cleaned inappropriately. Some general household cleaning products which contain certain solvents can cause softening of the finish resulting in peeling during use. Laboratory investigations have shown that even some proprietary cleaners and conditioners sold for use on leather can cause damage to the leather finish and accelerate the effects of normal wear and tear. BLC recommend that finished leather is cleaned only with a soft white cloth slightly dampened in a mild soap solution then wiped with a clean soft white cloth dampened in plain water. The leather should never be wetted or rubbed vigorously. Prevention Key points to minimise finish peeling are: * Correct preparation of the leather: check the penetration of fatliquor and silicon containing products into the grain surface. In the case of corrected grain leathers, make sure that the buffing and impregnation, if used, is adequate. * Correct finish formulation: ensure that the finish contains the right amount of penetrator, wax and binder. Make sure that top and basecoats are compatible. If at all possible, avoid over spraying - get it right first time. * Correct finish application: avoid heavy intermediate plating and ensure that drying is complete. * Correct advice: ensure that customers are advised in the correct care and cleaning of leather.