BLACKING. A preparation employed for produchm. a black, glazed. shining surface on leather.
producing arc numerous recipes for making blacking, but they all involve the use of a pigment, which is usually ivory-black, bone-blaek, or lampblack, mixed with a vehicle which is usually some combination of oil, vinegar, beer, molasses, water, and hydrochloric or sulphuric acids. Blacking intended for harness usually has glue, gelatin, g,nin arable, or some resinous compound added to the vehicle. The fact that the addition of snlphurie acid to ivory-Idack and sugar produces sulphate of lime and soluble acid phosphate of limp, which makes a tenacious paste. is the foundation of many of the com positions used as blacking. The famous English blacking known as Day & Martin's consists of bone-black. sperm-oil, molasses. vinegar, and sul phuric acid. These ingredients, when mixed to gether in the order named, produce a thick, tena cious paste, which is liquefied by the addition of vinegar, and put into stoneware bottles. A familiar recipe for a liquid blacking is as fol lows: Five ounces of ivory-black: • ounces of treacle: :5; ounce of sweet oil; triturate until the oil is thoroughly mixed in. then add one pint
each of vinegar and beer-lees. A paste blacking which may be easily made consists of ivory-black, 41 pounds; molasses, 3 pounds; hot sperm-oil, 9 minces; gum arabic, 1 ounce, and vinegar, 12 ounces. These ingredients are mixed together and allowed to stand for about a week, With an stirring, when the blacking is ready for use. By adding more A-inegar the compound may be liquefied. A well-known recipe for har ness-blacking is as follows: Beeswax, 1 pound; ivory-Idack. 1 i pound : Prussian bine, I ounce; ground in 2 ounces of linseed oil; oil of turpen tine, 3 ounces; copal varnish, 1 ounce; mix well together and form into cakes while warm. In founding (see FouNniNo) the name 'blacking' is given to various washes of powdered charcoal, sea-coal, or graphite with which the surfaces of models are coated to give the casting a smooth surface and to preveirt the molten metal from penetrating the same.