![]() There are many variations of Underline dials, both Open and Closed minute tracks. These are called "Underline" dials and were only used for a limited time in 1963. Of course, using a UV light or Geiger counter can easily confirm which material is present.Įarly Tritium dials were not identified as such until about 1962 when Rolex began to add a small round Lume plot under the 6:00 marker, sometimes called "Exclamation Dial." In 1963, Rolex marked dials with Tritium using a thin silver line. It can be difficult to tell which Lume has been applied under normal lighting and especially from pictures. A strong patina that develops can turn the markers an orange ochre color that can look virtually identical to Radium. It appears that at least two colors of luminous material were used, but since the Lume had a tendency to change shade and color with oxidation it is difficult to know with certainty. The same type of lacquer appears to have been used during this period and the Lume has a tendency to deteriorate. The texture and shape of the markers is very similar, as are the limitations on the quality and craftsmanship. Therefore, the Lume from this period shares many of the same characteristics as Radium. Glowie Tritium was also applied manually using the same techniques as Radium. ![]() It has a distinct glow that dims quickly when the source light is withdrawn, but continues to have a faint glow for some time afterwards. The moniker for the Lume from this period was coined dealers and collectors who wanted to describe the peculiar glow from this period. There is additional information pertinent information in the Geiger Section. Regardless, it is still helpful for collectors to have a Geiger counter and get familiarized with some of its readings on a variety of watches. The measurements can vary from one Geiger manufacturer to another and are influenced by other factors such as crystal thickness, Radium mixture and storage conditions. Radium Lume has a relatively active reading when measured with a Geriger counter, which is one of the methods collectors can use to determine if the Lume is original or has been reapplied. Unlike the other markers and hands, after exposure to light, the 6:00 marker dims quickly but continues to glow faintly for a time. Perhaps it was done to help divers orient themselves in depths without light? Although the texture is very similar to the other markers, the greenish white color is in contrast with the rest and glows much brighter under UV. It is interesting to note that circa 1955, for reasons that are not entirely clear, Rolex started applying a lighter and brighter Lume at 6:00 on Submariner models. But even after extended exposure to UV or even sunlight, the luminescence disappears in complete darkness. The Radium Lume has a dim but recognizable "speckled glow" when observed under a UV light. However, it cannot be understated that great care must be taken and the work should be performed by a dedicated professional. The good news is that it is possible to strengthen and preserve the existing Lume. There is no doubt that eventually the force of gravity will cause the Lume to crumble. Even the slightest contact with the Lume during service or strong jolt can shatter the fragile material. The gradual disappearance of the lacquer bonding component leaves the Radium in a more vulnerable state with each passing year. The lacquer component of the luminous mixture "gases out" or evaporates over time due to a normal chemical reaction caused by exposure to oxygen and humidity. Quality and consistency of the Lume application varied with experience and craftsmanship levels of the individuals who carried out the work. As a result, no two watches are exactly alike. The Radium luminous material was applied to dials and hands manually using a mixture of Radium and clear lacquer that acted as a bonding agent.
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