A quality indicator that usually depends on the age of the animal.
The thickness of the parchment determines the both the age of the animals and the specific features of the parchment production. Due to finer collagen fibres of the skins of young animals, the parchment (vellum) is evenly thin (0.08–0.04 mm) and elastic. The variance in the thickness of the split hides of young animals does not exceed 20%.
In the case of the skins of older animals, one-sided splitting along with the mechanical processing of the other side, i.e . double-sided splitting. The variance in the thickness is greater than 20%.