The luminous dial is a compromise. On the one hand, we want to be able to see the time in the dark without spending 100 odd dollars on a minute repeater. On the other hand, we also want our dials to age well, and it is inherent to many luminous materials that sooner or later they will dim to the point of uselessness. At this point, it is common to replace the dial and hands if you wish to be able to see at night as well – of course, if you do this with a vintage fake rolex for sale, whose high value lies in the originality of all the components, you may have a watch that can be read at night, but you will destroy its investment value.
This subject is one of the most interesting for collectors, yet there is still a widespread misunderstanding of how luminous materials actually work. Understanding the history of luminous watch dials and having a basic knowledge of the chemistry and physics behind luminous coatings can go a long way toward helping enthusiasts have a firmer foundation in distinguishing between originals or replacements, as well as understanding how to safely store and handle these sometimes dangerous materials.
The ability of a material to emit light in the dark is known as phosphorescence, which is a special case of photoluminescence. Photoluminescence is the ability of certain materials to emit light when exposed to light. Light is made up of packets of energy called photons (photons are quantum particles of the electromagnetic field). While the exact quantum mechanical description of photoluminescence is complex, the basic concept is simple: if an electron orbiting an atom in some material absorbs a photon, it will be excited to a higher energy state, and when the electron “relaxes” to its ground state, it will emit a photon, which we see as visible light.
The two types of photoluminescence that are familiar to most of us are fluorescence and phosphorescence. Fluorescent materials tend to emit the absorbed energy very quickly buy replica watches – they will glow as soon as a light source excites the material (often with what is called a “neon” color), but the time scale of emission is only nanoseconds, so they will turn black the moment the light source is removed. Anyone who has played with UV lights has seen materials emit fluorescence. These were commonly referred to as “black lights” and black light posters were a staple of the dorm in the 1970s (and for all I know, may still be).
