Definizione

• Torch Finish.  A method of coloring bronze medallic items in which a blowtorch is used to apply heat, hence the name. The coloring solution, often an acid, is applied with a brush, so the technician, called a patinaeur, heats up the object (or a small area of a large object) with the blowtorch – held in one hand – and a brush or cloth in the other hand applying the solution.
  Patina finishes in a variety of green and brown colors can be applied by torch finish. Many factors determine the ultimate color:  (1) alloy composition and (2) coloring solution, of course, but also (3) temperature of the torch and (4) the object; (5) number of applications and (6) manner of applying the solution. With so many variables satisfactory coloring only comes with long experience. The torch finisher's skill and artistry is important.
  Medals under 3-inch are heated with the torch and the solution is applied to the entire surface. Medallions and all other bronze objects larger than 3-inch are heated and solution applied to small areas at a time. The temperature – of both the torch and the object – is critical. Temperature is evidenced by the color of the flame, and here the experience of the torch finisher comes into evidence.
  Applying the solution is done with brush or cloth. Round, fairly stiff bristle brush works best with a stipple action, particularly for crevice areas. While smooth areas can be daubed with cloth or cotton wadding soaked with solution and squeezed – the solution should not flood the surface. Ideally the solution should sizzle in contact with the heated metal.
  Color is deepened or built up by repeated applications (or one color can be applied on top of a base color). Again skill and artistic experience of the operator will determine the final appearance. This process is widely used for bronze statues and other large objects, the technique remains the same, only the size is different.
  Medals are mounted on stilts, racks or prongs as they are heated by the blowtorch. The tiny areas on the edge where the medallic item comes in contact with the holder – usually at three equidistant points – is called rack marks. Coloring does not appear at these points of contact (unless, of course, the object is moved and colored again).
  Torch is one of several methods of metal coloring; others: immersion, applied, appressed, scratch brushed, sawdust and vapor. Perhaps only 5% of these methods are torch finishes but their importance rank them at the top for the permanence and beauty of their color on medallic metal surfaces.
  See also patina, finish and finishing.

  excerpted with permission from

  An Encyclopedia of Coin and Medal Technology

  For Artists, Makers, Collectors and Curators

  COMPILED AND WRITTEN BY D. WAYNE JOHNSON

  Roger W. Burdette, Editor

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