English Red (Angel Red, Iron Red, Venetian Red, Italian Red), is iron oxide that is used as a paint pigment, grinding or polishing agent. A distinction is made between: 1) Indian Red, red to rose red, is prepared in Bengal by beating very pure pieces of naturally occurring iron oxide and is used as a fine paint. Persian red and the powder obtained from bloodstone are similar, the latter is also used for polishing. 2) Polishing Red (Dead Head, Caput Mortuum, Colcothar Vitrioli), paint or polishing agent, a residue in the manufacture of Nordhäuser oil of vitriol, also obtained by annealing alum mud, evaporated mother liquors from the preparation of iron vitriol and from roasted pyrites, is a light brick red to dark purplish red, depending on the temperature at which it was made. With increased heat, the density, hardness and saturation of the preparation increase. Bright red soft Golden Red is used for polishing silver and gold, as well as a paint. The denser, darker Steel Red is used to polish steel, while the Iron Violet, obtained when it is incandescent, is used as a paint. Chemical Red, Nuremberg, Naples, French Red (Imperial, Royal, Berlin or Prussian Red, Brown Red) also belong here. A preparation for sharpening and polishing of steel goods, for strops is obtained by annealing equal parts of iron vitriol and common salt and boiling and washing out the residue. By annealing pure iron vitriol, two beautiful paint colours are produced, the darker Van Dyck’s Red and the lighter Mars Red. The finest polishing red for glass and metal is obtained by heating freshly precipitated oxalic iron oxide in an open iron bowl to 200-300°. See also Bole.
Source: Meyers Großes Konversations-Lexikon, 6. Auflage 1905–1909