1) Leather blackened by using water or vinegar mixed with either copperas or iron filings, a sort of black ink.
A term found from the late fourteenth century: 1398 to make stirrup lethyrs of blak barked lethir, York. It was a process that had to be checked by the searchers in the York shoemakers’ guild: 1417 si invenerint aliquod corium nigrum non tannatum, York. In 1491, the serssors of the cordweners agreed to pay 13s 4d annually to have ther old ordynaunces agayn delivered with serche of blake and rede lether, York, and in 1550-1 they had indentures drawn up with the Lord Mayor and his officers towchyng the grant of serche of blak leader onely and correction of all defalts in their craft .