Finishing defects on the leather

Marking off

 Causes:  Excessive quantities of brightening dyes or organic pigments inefficient amount of binders in the pigment finishes or top coats which have been applied too thin may result in making 

  Off of the finish.

Remedy:  Avoid the causes

 Cracking off

Causes:  Use of polymer binders which are not cold resistant very hard pigment finisher or top coats inadequate content of plasticizers or impaired adhesion of the individual finishes coats

Remedy: Avoid the causes

Powdering of Surface layers

Causes: Occurs in very hard causes finisher which have been applied in a very thick coat

Powdering of the entire finish coat

Remedy:  Reduce the thickness of coat. It is recommended that several thin coats be applied with intermediate drying. Addition of small amounts of polyacrylate dissolved in alcohol to the base coating agent prevents powdering of the finish coat.

Stripping of the finish    

Causes: impaired adhesion of the individual finish layers caused by an insufficient absorption capacity of the leather when applying the base coat and by inadequate reswelling of the preceding finish.

 Remedy: If the absorbing capacity is not adequate, use a penetrative pretreatment primer. Reduce the use of sealing, water-resistant binder. If using cross-linking binders continue processing without storing the leathers for a longer period as otherwise the film becomes insoluble by subsequent reaction.

Migration of plasticizers

Cause: Excessive drying temperatures direct application of nitrocellulose floats to the leather without previous base coating.

Remedy: Control the drying temperatures and if using nitrocellulose finishes apply a barrier layer on the basis of polymer binders.

Chalking

Causes: Caused in finish coats by migration of white pigment based on titanium oxide on exposure to light. Changes the shade of pastel colors. Contact with metals may also produce dark streaks.

Remedy: replace the white titanium oxide pigments by pigments based on zinc white which have a slightly reduced covering effect.

Fissure in the finish coat

Causes: Very high pliability of the leather and inadequate elasticity of the finish coats. Insufficient drying of polymer binders, especially if they contain organic solvents. These binders require a prolonged drying time as the finish films are solubilized and swelled.

Remedy: Use softer, more elastic finishing floats and dry each finish coat thoroughly.

Exudation of plastizers

Causes: If excessive amounts of non- gelatinizing plasticizer are used such as castor oil or rape oil, they may exude by storing the leathers in cool and warm places alternately or by ironing with excessive temperatures. Visible as a fatty on the leather surface.

Remedy:  Reduce the amounts of non-gelatinizing plastizers or choose a combination with gelatinizing plasticizers.