General introduction of Finishing and structure of finishing

The final product  of leather production reached with the finishing process. These treatments have the purpose of making the leather usable and suitable for the manufacture of end  products. The purpose of finishing is to lend to leather some kind off grain protection against soiling and water but also  the desired appearance, flexibility, color, gloss or dullness and handle. Furthermore, depending on the  end use, the finish has to meet some specific  performance characteristics  regarding dry and wet fastness, water  vapour and perspiration  permeability and high resistance to  staining by water droplets. 

The following properties of the leathers are to be achieved by application of different substances following final mechanical processing  depending  on the  type of leather:

1. Desired fashionable shades inn transparent, covering or effect finishes.
2. High-gloss , semi-matt or matt  top coats.
3. Dry waxy, greasy or  blunt surface  handle.
4. Leveling of stain patches and grain defects.
5. Protection against soiling, moisture and  process chemicals employed in  the manufacture  of finish products.
6. Application of fully covering artificial grain layer to splits and corrected  grain  leathers.

Structure of Finishes

1. Base  coat (Ground or bottom layer)
2. Pigment coat (Intermediate or middle layer)
3. Top coat (Final layer)

All coats aren't completely necessary their application depends on  the sorts of leather to be  produced. It's possible to selected intermediate stages or  to use the top coat  on its own. Basically, softer products are chosen for the  bottom layers, more durable and harder and more resistant  products for the top coat.

Typical coating stages - layers:

• Impregnation: To ensure good adhesion of coating layers, grain smoothness and tightness off the grain. It  will  be preceded by  spray staining (e.g. tier drum dyed shades).
• Base  coat: Accountable for the general look and levelness and uniform  distribution of pigment(s).
• Top coat: Crucial for final  look (e.g. gloss/ dullness, feel), handle, and in specially wet and dry rub fastness off the finish.

Intermediate coats are often applied to improve the adhesiveness and compactness of the coating They can also be called "the pigment coat" as most of the pigment particles remain embedded in the film forming materials of this  layer.

intermediate layers 

This layer can nicely be compared with a cement concrete slab, The void of the stone chips in concrete is filled up by sand and cement or in other words, thee stone chips remain embedded in thee slab formed by cement and sand mixture. I case of finishing the pigment particles are the stone chips whereas the film forming materials or binders like resin, shellac, casein etc., are thee sand/cement mixture. Like stone chips in concrete the pigment particles give body to thee finish layer and take the load or stress applied on the finish film. Over and above, these pigment particles give the desired shade completely cover up the defect on leather.