The tannins are vegetable, not synthetic, so every notebook becomes a unique piece, slightly different from all the others. For this reason, small imperfections in the leather should not be seen as defects, but as a sign of the authenticity of the article. Two processing methods are used for the notebooks: “dry” and “sublimation”, both with calfskin.
The “dry” method is used for notebooks with or without Tau embossed on the cover. This is the most commonly used printing technique in which the leather is permanently embossed using pressure and heat. The binding with long wraparound ribbon looks as if it comes from the time of the scribes when it was used to hold together the less important manuscripts that were not bound in the more expensive classic way; that is, by sewing and gluing the pages (almost always parchment) together to create the manuscript as we know it today.
Instead, “sublimation” is a technique in which pressure, temperature and steam are used to “inject” the pigments into the surface layer of the leather. Basically it could be likened to a permanent tattoo. This is also the reason why there is no 3D relief between the sublimated part and the hand-dyed leather part.