Different layers in finish coat:
The final film on leather is composed of mainly three layers which can be named as-
1. Ground or bottom layer
2. Intermediate or middle layer
3. Top or final layer
1.Ground layer:
The layer which remains in direct contact with the leather surface. Generally, a solution of a suitable film forming materials which may or may not be colored with acid dye is used for this purpose.
Objectives:
- To prepare a suitable base for the successive intermediate and top layers.
- To make the leather surface impermeable both ways to different materials.
- To provide better adhesion between leather surface and the film layer i.e. intermediate layer.
- To fill up the empty spaces between the corium major and corium minor for better break and tightness of the grain.
- To make, as far as possible, the leather surface smooth and uniform.
- To cover up the defects on leather surface to some extent.
2. Intermediate layer or Pigment layer:
The layer just above the ground coat is the intermediate layer or Middle coat and it
represents the major portion of the film thickness. This layer can also be called "the
pigment coat" as most of the pigment particles remain embedded in the film forming
materials of this layer. Like stone chips embedded in the slab pigment particles give the
body to the finish layer bear the load or stress applied on finish film. The pigment
particles also provide.
3. Top layer:
This is the final top-most layer resting on the intermediate one.
Objectives:
- To give required degree of gloss.
- To protect intermediate layer from scratch, frictional damages and abrasion.
- To make the finish film waterproof or at least water resistance
- To protect the leather from damages due to sweat, acids, alkalies and other injurious materials and vapours with which the leather may come in contact.
- To provide extra resiliency, feel and smoothness to the leather.
- To make the top surface of the leather ideal for embossing.
- To prevent mould or fungal growths.