Introduction
The word “finish” as a verb means bringing the task to an end or in another meaning is by completing the manufacture or decoration of (an article) by giving it an attractive surface appearance. (Dictionary). The same applies for leather when it reaches the final stage. The leather is now set to be modified and upgraded to give it more characteristics that meet with customer expectation. That’s why tanneries all around the world are putting more effort on the final stage in order to enhance and sell their leather.
After tannage, all classes of leather, whether vegetable or chrome tanned have to be finished to make them suitable to the purpose for which they will be ultimately used. With the exception of sole leather, finishing may broadly be said to consist of (i) dyeing or colouring, (ii) treating the leather with grease for softening and water-proofing (technically called currying) and (iii) polishing or glazing. But the finish imparted to leather is peculiar to it, so that no two varieties are finished the same way
Coming up with a finishing recipe high relays of different factors highly depending on what the customer wants. Giving an example when trying to achieve a shoe upper finish it differs from an upholstery finish. When finishing vegetable tanned leather it is neither dyed nor glazed. Its finishing is consisted in setting it out well to make it flat and smooth on the surface and pressing heavily to make it stiffer and water resistant. For chrome it differs it is run through more operation in order to achieve its final appearance starting with shaving in order to make the leather thin then neutralization taking place ending it up with stacking in order to make the leather softer then glazed to give it the glossy look and feel.
What is the purpose of finishing? The purpose of finish is done in order to enhance certain qualities and characteristics for example protecting the leather upgrading the leather look and feel by providing a texture which is waxier and smother.
Full grain leather can be addressed as the leather that does not go through the buffing stage and this is widely used when achieving furniture leather or automotive. Achieving a full grain can be expensive to most tanners. In order to achieve the natural grain of the leather it most not contain any marks or scratches, veins and putrefaction so it is very important on how to sort out your leather. The tanner should pick a good quality grade of crust leather in order to enable for finishing.
Corrected grain leather is known as chrome tanned side leather which is buffed with emery paper on the grain enabling it to remove the defects of the leather and then applied to it a plastic resin and pigmented finish to he help being built up on the leather usually this type of grain is used in the footwear industry.
Crust preparation
Crust is mentioned as the dried leather after tannage. And as it’s widely known as chrome leather ends up drying quickly and that results in leather becoming stiffer and making it harder when rewetting, drying usually occurs after any normal retanning and fatliquoring. leather that is exported around the globe in usually in this state while still many prefer at wet-blue or pickled stage because this gives them more ability of the leather process. When crust preparation applied for full grain leather or corrected grain leather both operations are related except for some procedures for example in buffing. Leading a leather from a crust stage to finishing still undergoes several procedures and also depends on the tanners recipe before receiving the end use .
Operations in common
for a
Chemicals used and finishing operation:
.
Finishing Recipes:
Casual Full grain upper footwear
Full Grain casual shoe recipe |
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1st coat |
2nd coat |
3rd coat |
procedure/remarks |
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Water |
75 |
500 |
100 |
1st x1 |
Adhesion |
|
RU 3961 |
25 |
light spray |
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DRY |
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RU 13-541 |
75 |
base coat |
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PP 39-111 BLACK |
100 |
light spray |
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RA 1246 |
250 |
Dry |
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FI 50 |
50 |
3rdx 2 |
top coat |
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BI 596 |
50 |
plate at 80 °C at low pressure |
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HM 51-760 |
5 |
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LW 5490 |
100 |
Adhesion Coat : Polyurethane with fine particles that is applied to pre base coating the main purpose of it is for achieving higher adhesion it also help in the flexibility.
Base Coat :
RU 1 3- 5 4 1: classified as soft polyurethane that is added during the base coat to help in the embossing characteristics. It gives out softer leather outcome.
P-P black : it is a pigment applied to the leather in order to give its color
RA 1-2-4-6: Classified as hard acrylic resin which enables a better gloos and ensures better results in the rub fastness
FI 5-0: Considered to be soft filler which gives a better plating and gives out a wax that helps giving the leather a more waxy feeling.
BI 5-9-6: Soft binder which gives a nore flazing look on the leather. Also helps in giving a good plated which is considered to be helpful during the embossing stage
Top Coat
HM 51-7 6 0 – A TYPE OF SILICONE HANDLING MODIFIER WHICH ENABLES GOOD SMOOTHNESS AND a silky like feel it also enhances resistance onto the leather
LW 5 4 9 0 : they are water based lacquer which gives a kind of gloss onto the leather .
Safety shoe Corrected grain upper footwear
Chemical Name |
Pre-base coat |
Base coat |
Top Coat |
Procedure |
Pigment 39-111 (Black) |
350 |
1. 1 X Roller Coater |
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Impregnation Resin ( RI-193) |
300 |
150 |
25-30 gms/ft |
|
Acrylic Resin (RA-2312) |
100 |
200 |
Leave Overnight |
|
Aromatic polyurethane ( RU-3969) |
50 |
Vaccum [email protected]*C/30s |
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Wax Filler ( FI-50) |
50 |
15 |
Buffing 320-340 (paper) |
|
Natural protein binder ( BI-1352) |
90 |
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Colloidal Filler ( FI-1208) |
15 |
2. 2 X Roller Coater |
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Water |
50 |
50 |
200 |
8-12 gms/ft |
Water Topcoat ( WT-2524) |
200 |
[email protected]*C 200P haircell |
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H |
Viscosity 20-25s (cup-4) |
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Penetrator ( PT-6591) |
100 |
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Crosslinker ( XR-5923) |
55 |
3. 2 x Spray |
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Rheology Modifier ( RM-4410) |
15-20 |
15-20 |
Mix crosslinker (water) |
|
Impregnation Coat
Base Coat
Top Coat
Comparison
in order to achieve a full grain leather the sorting of the leather many scares and defects on the skin will lower the end product of the finishing for the corrected grain leather its easier because the buffing will hide many of the scars and defects n the skin .when it comes to embossing full grain leather it depends it may be required and it may not be depending on the grain of the leather as for the corrected grain in order to give a better grain surface. When it comes to performance full grain leather will achieve higher performances than the corrected grain
Conclusion
All in all both are different than each other when its comes to physicality properties to achieve good results selection of crust must be made for full grain as for the corrected grain it does not require