TANNING PROCESS

HOME COLLECTIONS ABOUT LEATHER

 

1. Liming
A tannery does not know what kind of hide they have purchased until the hair has been removed. The process of removing the hair is called liming. Liming is accomplished by placing the hides in large narrow drums, shaped like a wheel. The drums rotate for many hours until all of the hair is removed.
   
  2. Selection and Sorting
The hides are then sorted as to their quality. The highest quality hides are those with the fewest markings. The least amount of work must be done to these hides to prepare them for finishing.
   
  3. Tanning
This process preserves the hide and makes its natural characteristics permanent. Tanning is accomplished by placing the hides into large rotating drums for 24 hours. These drums contain alkaline chrome salts. The hides emerge with a slight bluish tone. This state is called the "Wet Blue" state. This process enables current day leather to be softer and not to crack or peel.
   
  4. Splitting
The average thickness of a cowhide is 5mm. Upholstery leather requires a minimum thickness of .9-1.1mm. The hides are split in a splitting machine. This operation divides the hide in at least two hides: the grained hide and one or two splits.
 
   
  The strength of the fibers will vary with these hides. The fibers are very strong on the grained hide, and get weaker the deeper the split. The split has much less resistance and flexibility than the grained hide. These splits are processed as suede or embossed with graining to make it look like the grained hide. This is done to offer a lower price on some leather furniture.
   
  5. Finishing
     A. Aniline Color: At the beginning of the finishing process, hides are placed into the wheel-shaped drums to soften, remove excess water and apply an aniline dye. This means that they are dyed with color all the way through. The aniline dye penetrates completely through the entire hide. At this stage the hides are "pure top grain aniline". These superior hides (free from flaws) are then tumbled in drums for several hours to give added softness. This is called milling. These hides are now done. All other hides progress through additional surface treatments.
   
     B. Scar Correction - Buffing: Heavily scarred hides must receive correction. This correction is done by feeding them through a machine that is calibrated to the pressure needed to smooth out the hide. The graining is, therefore, lost in the process. These hides must later be embossed with "graining".
   
     C. Base Coat (Color): Hides then go through the process of receiving a consistent color over the entire surface. This color is close to the aniline color already received. This enables a less apparent color contrast, if the hide somehow gets ripped. At this point, the hide is considered protected, aniline dyed with a base coat of color. These leathers are uniform in color with the natural markings being covered.
   
     D. Top Coat (Clear): These hides then go through a clear coat finish. This seals the base color to the hide. The color will now not rub off or be damaged.
   
     E. Embossing: Because these hides were buffed smooth, the next process is embossing a grain into it. This is accomplished through heat and pressure. A hot plate is used which has the grain pattern etched into it. Lesser quality hides receive more buffing and embossing. With more embossing, the hide becomes firmer and less soft to the touch.
 

 
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