Characteristics of the film/ Ideal film:
1. Flexibility & stretchiness:
Leather is a flexible material with certain degree of stretchiness. If the film doesn't posses these properties to the same extent as leather, it will make the leather hard & the film will crack in course of time.
2. Adhesion:
The film should be firmly fixed to the leather surfaces so that the former doesn't come out during use. The film should also adhere to the pigment particles & others very firmly.
3. Holding power:
The film should have sufficient capacity to hold in it other substances like pigment, plasticizer etc. During drying or fill formation or ingredient of the finish should precipitate out.
4.Gloss:
The film should glaze by itself or should aquire this quality after glazing under glazing machine or hot plating or brushing.
5. Abrasive resistance & fastness:
The film should have sufficient resistance to abrasion for longer life & it should hold the coloring materials so tightly that it doesn't come out when rubbed with a dry & wet cloth.
6. Water proof-ness & water vapour permeability:
The film should repeal water so that the leather under it doesn't come in contact with water but it should allow water vapour to pass through. This is important for shoe upper leather.
7. Thickness:
The film should be as thin as possible so that it doesn't spoil the leathery appearance but the film should hide all the defects in the leather.
8. Resistance to acid, alkali & chemicals:
During use the leather comes in contact with dirt, mud, acid, alkali, sweat etc. This is specially common for leathers used by air, navi & army personnel in the field. So, the film should have sufficient capacity to protect the leather from these.