Finishing Techniques for Leather

Finishing Techniques for Leather Summery These papers make a brief clarification of some of the finishing technique which is to applied to two finishing procedure and clarification for full grain aniline leather finish and a full grain pigmented leather finish the material to be used in it and whey to apply such material for such both finishing type . also an observation on the needs for the finish for the leather . also a describe for the difference between the pigment and the dyes from their origin and behavior and other points of study for them . and after that an investigation about the organic and the inorganic pigment and the difference between them . plus a brief explanation about the comparison between cationic and ionic dyestuffs. more a study about two formulation for shoe upper finish for aniline and pigmented full grain leather plus study for the material to be applied for them . then end with product understanding from stahl mentioning their use and needs in the finish formulation and monitoring their behavior. Introduction Finishing The term finishing is applied in the leather industries to help enhance the properties and the appearance of the final piece of the leather its gives the leather more enhanced color and remove defaults that could be caused through the leather operation or a nature defect. The piece of leather is enhanced by treating it with dyestuff solutions, pigments, preparations, top coating then it enters he mechanical treatment in terms of plating. The basic rule in the leather finishing is the fewer blemishes on the raw hide The less finish has to be applied. The more grain layers is damaged layer is damaged, the more coats the leather required to replace The natural grain. Also the purpose of finishing is to provide different types of leather with special characteristics satisfy the requirement markets, The processes of finishing the leather give the leather upgrading of the following characteristics such as Color , brightness , matting , feel , softness , print pattern , water resistance and more . Part 1 Dyes and pigments Both dyes and pigments are powerful colorants material used to color other substances Pigments Pigments are the special type of dyeing material for wet processing technology. Pigment can also be define as a water insoluble coloring material and a coloring substance that makes the color of the product look different because of its absorption of certain wavelengths . dyes Dyes are substances found naturally and also made synthetically too . Dyes have the ability to change the color of the leather and material which they are applied. In earlier times, most of the dyes were obtained from plant sources , roots ,wood , stem bark and plants leaves . also in the 19th century synthetic dyes were produced and since then many of synthetic dyes have been produced . Special needs for the dyes in the surface coating where a high level of transparency is required, Dyes vs pigments Organic and inorganic pigments . The difference between organic pigments and inorganic pigment are based upon some principle factors. Such as Molecular structure of the pigments Carbon chains or carbon rings are always presented in the molecules of the organic pigments. But in the molecules of the inorganic pigments , the cations of metal are found in an array from the non-metalic anions . which with this arrangement does not allow these pigment to dissolve in the solvent . Source of pigments the main source of organic pigment are plants and plant products. The inorganic pigment are manufactured from topical cosmetic and dirt . Inorganic pigment are non-ferrous metal oxides , or some metal insoluble metal salts . Main difference between inorganic pigment and organic pigment Cationic and ionic dyes . Anionic dyes have a negative charge and attached to cationic surfaces, Cationic dyes have a positive charge and attached to anionic surfaces, The cationic dyes react with anionic sites on the surface of the substrate, the cationic produce a bright shades. The solubility of these dyes is very good in water in the presence of glacial acetic acid . Both anionic and cationic dyes have poor levelling properties . Part 2 One can ask the question. Why are there so many different types of leather ? simple answer is its all down to cost . The tanner should have the experience to sort and select the leather after the chrome tanning to forward each type leather batch selected and sorted to its category end use type product . The tanner forward the sorted chrome leather batches to the retanning and dying process. Such sorting is done according to the hide size, grain condition, surface grades , extra†¦ When it comes to finish the leather. The tanner already sort the leather in previous states So he knows what is he going to do with such sorted leather to apply the required finish to it . Almost all types of hides and skins can be finished . The final uses of the different leather leads to the type of the finishing to be applied . Type of the finish the tanner choose depend on the appearance he want sell his leather with it . Among of the types of finishing types of leather is. a – Aniline finish ( full grain aniline leather finish ) Aniline leather is the most natural looking leather with the unique surface characteristics of the hide remaining visible . To get such aniline leather you need to apply what’s called â€Å" aniline finish â€Å" Leather with an aniline finish is colored with dyestuffs only which means no opaque finish ie transparent finish so that the original grain surface can be seen through. Another transparent top coat can be applied to give bright finish and water repellent surface . Aniline finished leather has excellent tooling , polishing , and redyeing properties . B – Pigment leather finish ( full grain pigmented leather finish ) Such pigmented finish contains no aniline dyestuffs . the dyestuffs are all replaced with an opaque inorganic pigment , such mixture is bound together using a small amount of casein and a use of a binder ( mostely is thermoplastics type ) to form a continuous film , resulting in a more level finish and better coverage of the finish skin . The presence of such small amount of casein contained in the finish ensures the leather does not become sticky . After the leather is finally coated with a matt or bright water based lacquer emulsion to enable sealing the finish to give certain amount of resistance to wet , dry rubbing . Full grain aniline finish vs full grain pigmented finish