What does “luminous dial” mean on an old alarm clock?
With respect to vintage clocks, “Luminous dial” refers to hands, numbers, dots, etc. that are painted with a material that continues to glow after the ambient light in the room is turned off. It does NOT refer to an electric backlight behind the dial, as we see in newer electric clocks. These are usually referred to as “Lighted dials.” A little known fact is that the old luminous paint was mildly radioactive–actually, a form of radioactive cobalt and/or radium, mixed with phosphorescent paint. Everyone is familiar with the concept of phosphorescents, as they are used to coat the inside of TV picture tubes. When electrons strike the material, it glows. It is similar with luminous paint. Of course, it has been a long time since radium was used in luminous clock dials. The newer material is an acrylic material consisting of a long-persistence phosphorescent material, sensitive to photons (light). In the old days workers who would use their mouths to point up the brushes to paint luminous
With respect to vintage clocks, “Luminous dial” refers to hands, numbers, dots, etc. that are painted with a material that continues to glow after the ambient light in the room is turned off. It does NOT refer to an electric backlight behind the dial, as we see in newer electric clocks. These are usually referred to as “Lighted dials.
