Spanish leather was sumach tanned. This pale tannage allows truest dye colors. By the 1600's, sumach was imported into England; by the 1700's it was used to tan morocco leather. Vegetable dyes were used on moroccos mordanted with alum, while bark-tanned calf and sheep skins were colored by sprinkling or marbling. Sixteenth century russia leather was stamped with engraved steel cylinders. Degradation of leather manufacture began with the 1769 use of sulphuric acid to tan heavy leathers. With the advent of aniline dyes ca.1870, sulphuric acid was used to clear skins before dyeing. Leathers were judged on color brilliance and uniformity, not durability. In 1851, the electroplate process facilitated grain reproduction, and (weaker) sheepskin imitated morocco, pigskin etc. As bookbinding leather quality declined, buckram etc. flourished. Around 1900 a Committee on Leather for Bookbinding was appointed by the Society of Arts to create standards. The Council of the Library Association also appointed a Committee, supported by leather manufacturers who see that leather needs a standard of manufacture and honest trade descriptions to recover. Librarians should note: 1) Shabbiness, i.e. over edges: probable cause, sulphuric acid. 2) Red rot (powdery) morocco: probably sheepskin goat . 3) Withered and discolored pigskin: probably over pulling down during puering . 4) Deteriorated and discolored calfskins: probably bookbinder's use of oxalic acid to remove grease marks.