rays of a rough surface. The terms mirror, lustrous, medium, dull and dead reflectiveness express these degrees, which are created by the techniques listed on the adjacent chart.High reflective surfaces. The mirrorlike surface is due to extremely parallel light rays with uniform angle of refraction, thus displaying a reflected image. Full proof and prooflike metallic surfaces exhibit this phenomenon – both dies and planchets are polished to obtain a proof surface.Polishing or burnishing the struck or cast piece will create a highly lustrous surface. Luster can also be obtained chemically with a bright dip. Patina finishes that are lustrous are said to be glossy or semi-glossy.Low reflective surfaces. Dull or dead reflection results from a very irregular surface. The breaking up of a smooth surface – by matting tools, by acid etching or by abrasive blasting – produces a roughened surface. Light waves reflecting from such a surface are diffused – reflecting off in all directions, thus appearing dull.Reflective contrast. Some proof pieces are designed to have areas of both high reflective proof surface – generally the field or background because these are the high areas of the contrast of high and low reflectiveness. The matte areas are performed first by dilute acid etching, then the die is proof polished with diamond dust for the area requiring the mirror reflectiveness.Lustrousness. Striking a blank with dies in a press often creates some unusual reflectiveness phenomenon. Coining causes flow marks, minute striations on the surface of the struck piece. This may also cause iridescence or even a cartwheel effect on that same coined surface.Enemies of the reflective surface on a coin or medal are the same for any numismatic piece: tarnish, wear, handling and mishandling. Finger perspiration, contact with most chemicals or any abrasion reduces the reflective qualities. Haze and cleaning also reduce such reflectiveness. See proof finish, matte, tarnish.Any reflectiveness of any finish can be altered with the use of a lustrous lacquer. Patina finishes range from Gloss to Matte; although other surface treatments may be applied to a patina finish. See lacquer.Chart of ReflectivenessMedallic surfaces found on coins and medals.(In order of reflectiveness)Mirror *Full ProofProoflikeLustrousPolishedBurnishedBright DipGlossSemi-glossMediumSatin #Scratch BrushDullSemi-matteMatte (frosted)DeadSandblast or Abrasive Blast* Mirror finish – all proof finishes – are a productof the pressroom, not the finishing department. Theyare not a patina finish.# Satin reflectiveness should not be confused withsatin finish proof. See proof finish.
excerpted with permission from
For Artists, Makers, Collectors and Curators
COMPILED AND WRITTEN BY D. WAYNE JOHNSON
Roger W. Burdette, Editor