Abstract: Spiked plate (100) having an operating surface provided with a plurality of conical spikes (200), configured to penetrate into an inner side of a full grain natural leather having a thickness t and make blind holes in said inner side of the full grain natural leather, wherein:—a base diameter d of the conical spikes (200) ranges from 33% to 100% of the thickness t, whereby 0.33?t?d?t,—a height h of the conical spikes (200) ranges from 70% to 110% of the thickness t, whereby 0.7?t?h?t, and—a minimum distance D between the conical spikes (200) on the operating surface of the spiked plate (100) ranges from 200% to 430% of the thickness t, whereby 2?t?D?4.3·t.

Abstract: Method (1) for metal-free tanning of a quantity of hide having initial weight (w), said quantity of hide being contained in a drum, wherein said method (1) comprises at least one tanning treatment (B) of said hide including at least the following operating steps: B.1 feeding aliphatic aldehyde into said drum, in a percentage ranging between about 1% and 3% by weight with respect to the initial weight (w) of said hide, optionally equal to about 2% by weight, and B.2 moving said drum for a time period of at least about 10 min, optionally approximately 20 min at an operating speed between 1 and 8 revolutions/minute, preferably comprised between 4 and 5 revolutions/minute; B.3 feeding citric acid into said drum, in a percentage ranging between about 0.1% and 0.3% by weight with respect to the initial weight (w) of said hide, optionally equal to about 0.2% by weight, and B.4 moving said drum for a time period of at least about other 10 min, optionally approximately 20 min at said operating speed; B.

Abstract: Spiked plate (100) having an operating surface provided with a plurality of conical spikes (200), configured to penetrate into an inner side of a full grain natural leather having a thickness t and make blind holes in said inner side of the full grain natural leather, wherein:—a base diameter d of the conical spikes (200) ranges from 33% to 100% of the thickness t, whereby 0.33?t?d?t,—a height h of the conical spikes (200) ranges from 70% to 110% of the thickness t, whereby 0.7?t?h?t, and—a minimum distance D between the conical spikes (200) on the operating surface of the spiked plate (100) ranges from 200% to 430% of the thickness t, whereby 2?t?D?4.3·t.