Blacking

Blacking is the material employed for producing a black glazed shining surface on leather. The main ingredient in the various kinds of blacking is Bone-black (q.v.), which is mixed with an oil, some sugar, and a little sulphuric acid. The materials in Day & Martin's blacking are finely powdered bone-black ground with sperm-oil, raw sugar or molasses, a little vinegar, and some concentrated sulphuric acid (specific gravity 1843). The substances are incorporated together one by one in the order in which they are stated, and the action of the sulphuric acid is to convert much of the lime in the bone-black into sulphate of lime, which causes a thickening of the mixture, and a tenacious paste results. This paste, diluted with weak vinegar, is put, whilst warm, in stoneware bottles, and is then ready for the market. For harness the blacking consists mainly of beeswax, softened with turpentine, and mixed with ivory-black, Prussian blue, and copal varnish.