As we can see from the picture below, the hide, for its nature, it is not homogeneous but changes from point to point in resistance, in firmness and in elasticity.
Resistance to traction > 1,7 kg/mm2
Extension to breaking point > 60%
Resistance to traction > 1,7 kg < 2,6 kg/mm2
Extension to breaking point > 26% < 60%
Resistance to traction > 2,6 < 3,5 kg/mm2
Extension to breaking point > 20% < 26%
Resistance to traction > 3,5 kg/mm2
Extension to breaking point > 20%
One of the main aims to obtain from the various operations of tanning is the reduction of the differences from hide to hide and from a single zone of the hide to another, but despite all efforts, it is not possible to have a real and complete homogeneity.
Even in the case of shoe leather, hides are worked, sold and divided in single parts (shoulders, sides, croupons) which have differences in characteristics and in prices.
These differences are one of the main characteristics of the hide which make its working more complex than fabric. What on the contrary makes leather more workable than fabric is its isotropicity, or better, its resistance and elasticity almost equal in all directions. It is evident that in a fabric, on the contrary, there is a low elasticity in the direction of the warp, an elasticity a little bit higher in the direction of the weft and an extreme elasticity and deformability in the diagonal direction. This means that while on a fabric the pieces of a sofa have to be cut always in the same direction, on the hide pieces can be rotated without any significant consequences.
We remind you that apart from the differences in the natural origin of the hide, there is also a long list of differences intentionally caused by the different process operations in order to give peculiar characteristics to each article. It is important to not to forget that each process has positive and negative effects, and consequently while the final aspect of the sofa will be improved by the positive aspects, the process will be penalised by the negative effects, binding the possible processes to the type of leather used. Therefore we can say that as few sofa models can be obtained with a type of leather, also very few types of leathers can be adapted to a singular and precise sofa model.
Every sofa, to come out at its best, needs its “own” leather.